A Study on Utilization of Recycled Aggregate and Fly Ash ...

A Study on Utilization of Recycled

Aggregate and Fly Ash to Reduce

Environmental Load :

Application of Pulsed Power

Technology for Reconstruction of

the Great East Japan Earthquake

September 2014

ARIFI, Eva

GRADUATE SCHOOL OF SCIENCE AND TECHNOLOGY

KUMAMOTO UNIVERSITY

i

ABSTRACT

Great East Japan Earthquake which occurred in March 2011 and hit Fuku-

shima Nuclear Power Plant has spread radioactive substances into the atmos-

phere, soil, and water. Enormous amount of contaminated concrete debris from

collapsed reactor buildings, and other structures with high radioactivity need to

be disposed. However, due to the large amount of waste, without proper treat-

ment, landfill and cost required is very expensive. Therefore, an effective

method to reduce radioactive waste, especially contaminated concrete waste is

urgently needed.

In this study, the pulsed power technology is proposed as a decontamina-

tion method by reclaiming aggregate from contaminated concrete waste to re-

duce the volume of contaminated concrete waste. This method is applied be-

cause it can produced high quality recycled aggregate, which can separate mor-

tar from aggregate. As the radioactive contamination was mainly concentrated

in cement paste, the aggregate reclaimed from contaminated concrete waste,

therefore, can be recycled as aggregate.

In addition, it is expected that after the Great East Japan Earthquake the

coal-fired power plants are extensively in service and rapidly expanding to

meet the electricity demand. It means that the amount of fly ash as a by-

product of the combustion of coal-fired power plant should also increase.

Hence, the utilization of fly ash to mitigate environmental load is needed. Fly

ash was utilized as cement replacement and fine aggregate replacement. This

study, focusing on the utilization of fly ash and recycled aggregate produced by

pulsed power technology, sustainable construction is proposed and studied.

ii

Keywords: Contaminated concrete, recycled aggregate, fly ash, pulsed power,

two-stage mixing approach

iii

ACKNOWLEDGEMENT

All praises to Allah for bestowing His mercy and blessing in completing

my doctoral thesis. Foremost, I would like to express my sincere gratitude and

appreciation to my supervisor, Prof. Mitsuhiro Shigeishi, for his kindness, con-

tinuous support, patience, motivation, and immense knowledge in this research

work. My gratitude will never be enough to illustrate how much I thank him. I

would not be able to finish this thesis without his valuable assistance.

I would like to offer my special thanks to Prof Masayasu Ohtsu. His advice

and comments has been a great help in writing my thesis and journal papers. I

also would like to thank to other committee members, Prof. Toshitaka Yamao,

Assoc. Prof. Takao Namihira, for their valuable suggestions and insightful

comments.

My sincere thank goes to Dr. Yuichi Tomoda, Dr. Shinya Iizasa, and Mr.

Yasuo Miyazaki for their meaningful assistance during my research. My great

appreciation to my colleagues in Concrete Laboratory of Kumamoto University,

Retyce Ivan Herve Amoussou, Koichi Ishimatsu, Nobuyasu Oyama, Naoya

Honda, and Youhei Takanabe, also Dr. Achfas Zacoeb from Brawijaya Univer-

sity Indonesia for their great efforts in supporting my experiments. Many

thanks also goes to Ayako Sako, Shota Tajiri, Kentarou Nakao, Seiya Togoe,

Misaki Kira, Yusuke Nagai, and Yutarou Kawasaki, for their help and friend-

ship during my course.

I would like to thank to Mr. Hiroyuki Sakamoto from Taiheiyo Consultant

Co., Ltd. for his support in the analysis of Cs content of my samples, Dr. Ya-

suhiro Dan, Mr. Sinya Hiramoto, and Mr. Yusuke Ohtsuka from Nippon Steel

iv

& Sumikin Blast Furnace Slag Cement Co.,Ltd., for providing GBBS cement,

Mr. Masaru Watanabe and Mr. Sadao Fujibata for providing fly ash material,

Mr. Hiroshi Matsumoto and Mr. Yuji Yamashita from Khusu Electric Power

Co., Inc. for giving valuable information about fly ash, Dr. Sadanori Kusunoki

and Dr. Shinya Iizasa from West Japan Engineering Consultants, Inc., for their

precious advice on fly ash concrete. Their supports have provided substantive

input to my thesis.

I also would like to thank to Japan Society for the Promotion of Science

JSPS KAKENHI, The Global COE Program on Pulsed Power Engineering at

Kumamoto University supported by the Ministry of Education, Culture, Sports,

Science and Technology (MEXT) in Japan, and Ministry of Economy, Trade

and Industry (METI) in Japan for financially supporting my research.

Innumerable thanks to the Directorate General of Higher Education, Min-

istry of National Education of the Republic of Indonesia for granted me the

Doctoral Scholarship in Kumamoto University.

Special thanks to my twin sister, Evi Nur Cahya, for her accompaniment

wading through this life. It would not be the same without her. Many thanks to

Ratu Fatimah for the friendship and togetherness.

Most importantly, none of this would have been possible without the love

and patience of my family to whom this thesis is dedicated to. Therefore, I

would like to express my heartfelt gratitude to my beloved parents, my dearest

husband and my lovely sons for their endless prayers, support, and trust.

v

Table of Contents

ABSTRACT ......................................................................................................... i

Table of Contents .............................................................................................. iii

List of Figures ................................................................................................. viii

List of Tables....................................................................................................... x

1 Introduction ................................................................................................... 1

1.1. Background ........................................................................................... 1

1.2. Objectives of Study ............................................................................... 3

1.3. Outline of Thesis ................................................................................... 4

2 Theoretical Background ................................................................................ 9

2.1. The Growth of Utilization of Concrete ................................................. 9

2.2. Concrete Waste ................................................................................... 11

2.3. Waste Generated by Great East Japan earthquake .............................. 12

2.3.1. Decontamination Method ............................................................ 13

2.3.2. Regulation for Disposal of Radioactive Waste ........................... 14

2.4. Recycled Aggregate from Concrete Waste ......................................... 14

2.4.1. Utilization of Recycled Aggregate .............................................. 15

2.4.2. Properties of Recycled Aggregate ............................................... 16

2.4.3. Specification of Recycled Aggregate .......................................... 16

2.4.4. Properties of Recycled Aggregate Concrete ............................... 17

2.5. Fly Ash ................................................................................................ 18

2.5.1. Composition of Fly ash ............................................................... 18

2.5.2. Utilization of Fly ash in Concrete ............................................... 19

2.5.3. Specification of Fly Ash.............................................................. 20

vi

2.5.4. Properties of Fly Ash Concrete ................................................... 22

2.6. Pulsed Power Technology to Produce High Quality Recycled

Aggregate ....................................................................................................... 22

2.6.1. Procedures of Reclaiming Aggregate by Pulsed Power

Technology ................................................................................................. 22

2.6.2. Properties of Recycled aggregate Produced by Pulsed Power

Technology ................................................................................................. 24

3 Application 1 : Reduction of Radioactive Contaminated Concrete by Pulsed

Power Discharged ............................................................................................. 32

3.1. Introduction ......................................................................................... 32

3.2. Objectives ........................................................................................... 33

3.3. Contaminated Concrete ....................................................................... 33

3.4. Pulsed Power Technology to Reduce Contaminated Concrete Waste 34

3.5. Experiment .......................................................................................... 35

3.5.1. Material Used .............................................................................. 35

3.5.2. Mixture Proportion ...................................................................... 36

3.5.3. Contaminated Concrete Simulation ............................................ 36

3.5.4. Cs Penetration into Concrete Specimen ...................................... 37

3.5.5. Crushing by Pulsed Power Discharge ......................................... 37

3.5.6. Cs Distribution Analysis for Reclaimed Aggregate .................... 37

3.6. Result and Discussion ......................................................................... 38

3.6.1. Quantity and Quality of Reclaimed Aggregate ........................... 38

3.6.2. Cs Distribution Result ................................................................. 39

3.6.3. Discussion on Japan Government Regulations for Radioactive

Waste Disposal ........................................................................................... 41

3.7. Conclusion .......................................................................................... 42

4 Application 2 : Strength and Shrinkage of Concrete Made From Rrecycled

Aggregate by Pulsed Power Technology with Fly Ash as Cement Replacement

........................................................................................................................... 47

vii

4.1. Introduction ......................................................................................... 47

4.2. Objectives ........................................................................................... 48

4.3. Research on Fly Ash Concrete Made From High Quality Recycled

Aggregate ..................................................................................................... 48

4.4. Experiment .......................................................................................... 50

4.4.1. Material Used .............................................................................. 50

4.4.1.1 Aggregate .................................................................................. 50

4.4.1.2 Cement and Fly Ash .................................................................. 52

4.4.2. Experiment Procedures ............................................................... 54

4.4.2.1 Mix Proportion .......................................................................... 54

4.4.2.2 Specimen Casting and Curing ................................................... 54

4.4.3. Test Method ................................................................................ 55

4.4.3.1 Fresh Concrete Properties ......................................................... 55

4.4.3.2 Hardened Concrete Properties .................................................. 56


4.5.1. Properties of Fresh Concrete ....................................................... 56

4.5.2. Properties of Hardened Concrete ................................................ 57

4.5.2.1 Compressive Strength ............................................................... 57

4.5.2.2 Tenslie Splitting Strength.......................................................... 60

4.5.2.3 Modulus of Elasticity ................................................................ 61

4.5.2.4 Drying Shrinkage ...................................................................... 61

4.6. Conclusion .......................................................................................... 65

5 Application 3 : Performance of Fly Ash Concrete Made of Recycled

Aggregate by Pulsed Power Technology with Two-Stage Mixing Approach 70

5.1. Introduction ......................................................................................... 70

5.2. Objectives ........................................................................................... 71

5.3. Two-Stage Mixing Approach ............................................................. 71

5.4. Research on Fly Ash Concrete Made of Recycled Aggregate Concrete

with TSMA .................................................................................................... 72

viii

5.5. Experiment .......................................................................................... 73

5.5.1. Material ....................................................................................... 73

5.5.1.1 Aggregate .................................................................................. 73



5.5.2.1 Mix Proportion .......................................................................... 75


5.5.3. Test Method ................................................................................ 77

5.5.3.1 Fresh Concrete Properties ......................................................... 77

5.5.3.2 Hardened Concrete Properties .................................................. 77


5.6.1. Properties of Fresh Concrete ....................................................... 77

5.6.2. Properties of Hardened Concrete ................................................ 79

5.6.2.1 Compressive Strength ............................................................... 79

5.6.2.2 Tenslie Splitting Strength.......................................................... 81

5.6.2.3 Modulus of Elasticity ................................................................ 82

5.6.2.4 Drying Shrinkage ...................................................................... 83

5.7. Conclusion .......................................................................................... 86

6 Application 4 : Effect of Fly Ash as Partial Replacemnet of Low Quality

Fine Aggregate on the Performance of Mortar ............................................... 91

6.1. Introduction ......................................................................................... 91

6.2. Objectives ........................................................................................... 92

6.3. Research on Fly Ash as Partial Replacemnet of Fine Aggregate ....... 92

6.4. Experiment .......................................................................................... 93

6.4.1. Material ....................................................................................... 93

6.4.1.1 Fine Aggregate .......................................................................... 93



ix

6.4.2.1 Mix Proportion .......................................................................... 96


6.4.3. Test Method ................................................................................ 97


6.5.1. Compressive Strength ................................................................. 97

6.5.2. Flexural Strength ......................................................................... 99

6.5.3. Drying Shrinkage ...................................................................... 101

6.6. Conclusion ........................................................................................ 102

7 Conclusion .............................................................................................. 106

x

List of Figures

2.1 World cement production ......................................................................... 10

2.2 Resources into construction sector in Japan............................................. 10

2.3 Waste output from construction industries in Japan ................................ 11

2.4 Changes in coal ash generation and utilization rates ............................... 20

2.5 Process of crushing the concrete waste by pulsed power technique ........ 23

2.6 Concrete waste was discharged by pulsed power .................................... 23

2.7 Discharge pass in concrete ....................................................................... 23

2.8 Relations between reclaimed coarse aggregate and number of pulsed

power shots ....................................................................................................... 25

2.9 Reclaimed materials by pulsed power discharge ..................................... 25

3.1 Scheme of contaminated concrete waste.................................................. 34

3.2 Reclaimed aggregate on the mesh electrode ............................................ 38

3.3 EPMA result ............................................................................................. 39

4.1 Appearance of recycled aggregate concrete by pulsed power discharge . 51

4.2 Coarse aggregate particle size distribution .............................................. 52

4.3 Slump and air content result ..................................................................... 56

4.4 Compressive strength of specimen made of natural coarse aggregate ..... 58

4.5 Compressive strength of specimen made of recycled coarse aggregate .. 59

4.6 Compressive strength of specimen .......................................................... 60

4.7 Tensile splitting strength .......................................................................... 61

4.8 Modulus of elasticity ................................................................................ 62

4.9 Drying shrinkage of specimen made of natural coarse aggregate ............ 63

4.10 Drying shrinkage of specimens made of recycled coarse aggregate......... 63

4.11 Drying shrinkage of specimens without fly ash ........................................ 64

4.12 Drying shrinkage of specimen with 10% fly ash as cement replacement . 64

4.13 Drying shrinkage of specimen with 25% fly ash as cement replacement 65


5.1 Coarse aggregate particle size distribution .............................................. 73

5.2 Slump and air content result ..................................................................... 78

5.3 Compressive strength of specimen made by normal mixing approach.... 79

xi

5.4 Compressive strength of specimen made by two-stage mixing approach80

5.5 Compressive strength of specimens ......................................................... 81

5.6 Tensile splitting strength .......................................................................... 82

5.7 Modulus of elasticity of concrete specimens ........................................... 83

5.8 Drying shrinkage of specimen made by normal mixing approach ........ 83

5.9 Drying shrinkage of specimens made by two-stage mixing approach ..... 84

5.10 Drying shrinkage of specimen without fly ash ......................................... 85

5.11 Drying shrinkage of specimen with 25% fly ash as cement replacement

........................................................................................................................... 85


6.1 Size distribution of crushed stone sand and standardized sand ............... 94

6.2 Compressive strength of mortar specimens ............................................. 98

6.3 Flexural strength of mortar specimens ..................................................... 99

6.4 Drying shrinkage of mortar specimens .................................................. 100

xii

List of Tables

2.1 Definitions regarding oven-dry density and water absorption ratioof

recycled aggregate under JIS classification .................................................... 17

2.2 Quality of fly ash (JIS A 6201) ................................................................ 21

3.1 Radioactive Cs contents of debris ............................................................ 33

3.2 Properties of aggregate for specimens ..................................................... 36

3.3 Mixture proportion for concrete specimens ............................................. 36

3.4 Distribution of Cs in reclaimed materials by ICP-MS ............................. 40

4.1 Recycled coarse aggregate physical properties ........................................ 51

4.2 Sieve analysis of recycled coarse aggregate ............................................ 51

4.3 Physical properties of portland blast furnace cement .............................. 53

4.4 Chemical properties of portland blast furnace cement ........................... 53

4.5 Properties of fly ash ................................................................................. 53

4.6 Concrete mix proportion .......................................................................... 54


5.1 Recycled coarse aggregate physical properties ........................................ 74




5.5 Concrete mix proportion and mixing approach ....................................... 76

5.6 Concrete fresh properties ......................................................................... 78


6.1 Fine aggregate physical properties ........................................................... 93

6.2 Sieve analysis of crushed stone sand ....................................................... 93

6.3 Sieve analysis of standardized sand ......................................................... 94




6.7 Mortar mix proportion ........................................................................... 96

6.8 Compressive strength of mortar specimens ............................................. 98

6.9 Flexural strength of mortar specimens ..................................................... 99

1

CHAPTER 1

Introduction

1.1. Background

A huge magnitude 9.0 earthquake triggered tsunami which hit east part of

Japan in March 11, 2011. As a result, Fukushima Daiichi Nuclear Power Plant

not only suffered heavy damage, but also caused the spread of radioactive

substance released into soil, atmosphere and water, irradiating a large amount

of debris from collapsed structures in area near Fukushima plant site. Great

East Japan Earthquake has brought Japan facing new phase to deal with the

waste problem.

According to Ministry of the Environment, the Great East Japan

Earthquake left behind a vast amount of disaster waste and Tsunami deposit in

13 prefectures of eastern Japan, which mostly affected in Iwate, Miyagi and

Fukushima prefectures. The total amount of disaster waste was estimated 26.18

million tons [1]. This amount includes tsunami sediment and concrete debris.

From the total amount of waste concrete, some of which contain high levels of

radioactivity, particularly in the area of the power plant building. Moreover, it

CHAPTER 1 Introduction

2

is also estimated that concrete waste from the collapsed reactor building as well

as other structures and pavements needed to be demolished after the plant settle

down are enormous.

Unlike other typical waste, radioactive waste requires special handling

because radiation can be harmful to human health. It requires an effective

decontamination method considering the number and the danger of radioactive

waste, including contaminated concrete waste. As a country that is very

concerned about its preservation of the environment, since 2006, the scale of

concrete recycling has reached 98% to be reused as recycled aggregate for road

sub-base, underground stabilization and non-structural concrete [2]. Therefore,

decontamination of contaminated concrete waste has provided another serious

attention.

In this study, the application of pulsed power technology is proposed as a

decontamination method to reduce contaminated concrete waste. Pulsed power

has been proven to produce high quality recycled aggregates because it can

separate mortar from aggregate thoroughly. The quality of recycled aggregate

is controlled by the energy and number of discharge treatment [3]. This

technique is proposed as a decontamination method because the previous study

has shown that radioactive is concentrated mainly in the porous fine cement

paste [4]. Therefore, the application of pulsed power technology is found to be

promising as the decontamination method.

On the other hand, Great East Japan Earthquake has provided a valuable

lesson on awareness of nuclear safety and radioactive accident that can occur

beyond human control. After the Fukushima accident, nuclear power plants in

Japan have been discontinued. Filling this gap, coal-fired power plants become

alternative replacing nuclear power plant to meet electricity demand.

Thus far, the nuclear power belongs to the range of energy sources and

technologies available today that could help meet the climate–energy challenge.


3

Global greenhouse gas emissions from nuclear power plants are negligible and

nuclear power, together with hydropower and wind based electricity, is among

the lowest CO2 emitters when emissions over the entire life cycle are

considered. Nuclear power remains economically competitive and its position

is further enhanced by the increasing CO2 costs of fossil based electricity

generation [5]. Conversely, coal fired power plants have the highest

greenhouse gas emission intensities on a lifecycle basis [6]. Impact of coal-

fired power plants also poses serious environmental problems due to waste

materials generated from the combustion of coal, especially fly ash as a residue.

It has been reported that the production amount of coal ash in Japan

exceeded over 10 million tons. This amount is expected to increase due to new

construction and expansion of coal-fired power stations. However, the relative

amount of fly ash in use for concrete is low as compared with the case used for

raw material in the cement manufacturing process [7], [8]. Utilization of fly ash

as a supplementary cementitious material can promote sustainable construction

by reducing the CO2 emission of cement production.

To support the environmental conservation in creating sustainable

construction, an effective and efficient solution tackling the problem of

environmental load in reconstruction following Great East Japan Earthquake is

needed, either reproducing or reusing recycled aggregate by the pulsed power

technology from contaminated concrete waste, as well as studies on the

utilization of fly ash, residue of coal-fired power plant, as construction material.

1.2. Objectives of Study

a. Application of reclaiming aggregate from radioactive concrete using the

pulsed power discharge as the decontamination method to reduce the

volume of radioactive concrete due to Great East Japan Earthquake


4

b. Evaluation on the performance of fly ash concrete made from recycled

aggregate by the pulsed power technology to reduce environmental load

due to transition of nuclear power plant to coal-fired power plant in Japan.

c. Evaluation on the improvement of performance of fly ash concrete made

from recycled aggregate concrete by the pulsed power discharge with two-

stage mixing approach.

d. Evaluation on the performance of mortar with fly ash as low quality fine

aggregate replacement.

1.3. Outline of Thesis

The dissertation consists of seven chapters. Chapter 1 presents an

introduction of the thesis, including background and objectives. This chapter

describes the large amount of environmental load caused by Great East Japan

Earthquake. It proposes the pulsed power technology as an effective

decontamination method to reduce the volume of contaminated concrete waste.

Furthermore, the possibility of coal-fired power plant growth to meet

electricity needs after nuclear power plants were discontinued is presented. It

gives consequence enhancing the utilization of fly ash generated from coal

combustion to be reused as construction material rather than to be sent to

landfill. This chapter also gives the outline of the thesis.

Chapter 2 firstly illustrates the growth of utilization of concrete and its

effect to the environment, especially in generating construction and demolition

waste. In addition, the current situation of radioactive waste due to Great East

Japan Earthquake is also discussed. In this chapter, theoretical background of

recycled aggregate and fly ash as construction material are presented. The

development of the utilization of recycled aggregate and fly ash are also

described along with its properties when used in concrete. Further, the pulsed


5

power as a technique to reproduce high quality recycled aggregate is

introduced.

Chapter 3 presents the application of reduction of radioactive contaminated

concrete by the pulsed power discharged. The experimental study on the

effectiveness of pulsed power as the decontamination method of radioisotope

Cs is investigated. Limestone aggregate was selected in concrete specimen

because this type of aggregate is soluble in acid which used in the distribution

analysis of Cs. Concrete specimens was immersed in the aqueous solution of

CsCl using stable isotope to simulate contaminated concrete. ICP-MS was used

to analysis the distribution of Cs in the reclaimed aggregate discharged by

pulsed power technology.

Chapter 4 discusses the effect of fly ash as cement replacement on the

strength and durability of concrete made from recycled aggregate by the pulsed

power technology. Natural coarse aggregate concrete was used as a controlled

specimen to compare with concrete made from recycled coarse aggregate by

the pulsed power technology. The natural coarse aggregate was set to have

similar particle size distribution as recycled aggregate concrete. Compressive

strength, tensile splitting strength and drying shrinkage of both concrete with

fly ash as partially cement replacement are investigated.

Chapter 5 continues to evaluate the performance of fly ash concrete made

from recycled aggregate by the pulsed power technology. In Chapter 4, the fly

ash concrete made from recycled aggregate was produced by Normal Mixing

Approach (NMA), while in this chapter, the strength and durability of fly ash

concrete are improved with the application of Two Stage Mixing Approach

(TSMA).

Chapter 6 presents the evaluation of fly ash as partial replacement of low

quality fine aggregate on the performance of mortar. JIS standardized sand was

used as a control specimen of mortar. Crushed stone sand as low quality fine


6

aggregate was replaced partially by fly ash to increase the utilization of fly ash

in concrete. Compressive strength test, flexural strength test, and drying

shrinkage measurement are conducted to investigate the performance of fly ash

in replacing fine aggregate.

The last chapter summarizes the results obtained from Chapter 2 through 6.


7

Bibliography

1. Ministry of the Environment, “Disposal of Disaster Waste”, Annual Re-

port of the Environment, The Sound Material-Cycle Society, and Biodi-

versity in Japan, 2013

2. Iizasa S, Shigeishi M, Namihira T, “Recovery of high quality aggregate

from concrete waste using Pulsed Power Technology”, Clean Technology

2010, www.ct-si.org, ISBN 978-1-4398-3419-0,2010

3. Narahara S, Namihira T, Nakashima K, Inoue S, Iizasa S, Maeda S, Shi-

geishi M, Ohtsu M Akiyama H, “Evaluation of concrete made from recy-

cled coarse aggregates by pulsed power discharged”, 1-4244-0914-4/07,

2007 IEEE., Kumamoto University, 2007

4. Choi W. K., Min B. Y., Lee K.W., “Volume reduction of dismantled con-

crete wastes generated from KKR-2 and UCP “, Nuclear Engineering and

Technology, Vol. 42, No.2, April 2010.

5. International Atomic Energy Agency, “Climate change and nuclear power

2013”, Vienna, 2013

6. World Nuclear Association, “ Comparison of lifecycle greenhouse gas

emission of various electricity generation sources”, WNA Report, July,

2011

7. Sugiyama T, “Durability of Fly Ash Concrete in Salt-laden Environment”,

Third International Conference on Sustainable Construction Materials and

Technology Proceeding, August 18-21, 2013

http://www.ct-si.org/


8

8. Ishikawa Y, “Research on the quality distribution of JIS type-II fly ash in

Japan”, Sugiyama T, “Durability of Fly Ash Concrete in Salt-laden Envi-

ronment”, 2007 World of Coal Ash (WOCA), May 7-10, 2007

9

CHAPTER 2

Theoretical Background

2.1. The Growth of Utilization of Concrete

No denying that concrete has become the most widely consumed

construction material in the world. Its strength and durability, low maintenance,

fire resistance, energy saving and its aesthetic value are a few reasons that

make this material remains a favorite. Nowadays, more than 20 billion tons of

concrete has been consumed annually in the world. Its primary component

materials are aggregate, cement and water, with aggregate constituting

approximately 70% of total volume which can be found locally easily has made

concrete become the most bountiful resources on earth [1]. According to

CEMBUREAU activity report 2012, 3.6 billion tons of cement has been

produced in the world as shown in Fig. 2.1. It indicates the magnitude of

concrete demand in the world.

CHAPTER 2 Theoretical Background

10

Fig. 2.1 World cement production 2012 [2]

While in Japan, according to a White Paper on the Environment (Ministry of

Environment 2003), the total material input ranged from 2.0 to 2.2 billion tons

annually in recent years, of which 1.0 to 1.1 billion tons (50 percent) were

accumulated every year in the form of building and civil structure [3] as shown

in Fig. 2.2 This fact indicates the vast amount of resource consumption by the

construction sector as compared to other industrial sectors. Furthermore,

concrete production in Japan has reached 500 million tons per year. This means

that half of the consumption of resources is the use of concrete materials [3].

Fig. 2.2 (a, b) Resources input into construction sector in Japan [3]


11

However increased use of concrete as a result of population growth also

poses environmental problems, such as CO2 emission due to cement production,

resource depletion and waste disposal. It responsible for 5% CO2 production in

the world [4]. A large amount of aggregate used in concrete, indeed contributes

to natural resource depletion. While 40% of all industrial waste is construction

and demolition [5], concrete waste also requires an extensive landfill disposal.

2.2. Concrete Waste

As the most used materials, concrete donated large amounts of waste. From

the total of 458.36 million tons per year of waste in Japan, construction waste

has reached 79 million tons per year or 17% of the total waste. In fact, 35

million tons of the construction waste is concrete lump with average 42% of

the total construction waste as illustrated in Fig 2.3 [3]. Due to a large amount

of concrete waste, Japan has developed waste management to reduce the

volume concrete waste. Since 2006, 98% of concrete waste has been recycling

to be reused as recycled aggregate [6].

Fig. 2.3 Waste output from construction industries in Japan [3]

(a) Total waste; (b) construction waste


12

2.3. Radioactive Waste Generated by Great East Japan

Earthquake

At 14:46 on March 11, 2011, a massive 9.0 earthquake of magnitude struck

the Tohoku and Kanto regions, triggering a giant tsunami that inundated the

Pacific Coast of Japan. The epicenter of the earthquake was off the Sanriku

Coast at latitude 38.1° north and longitude 142.9° east. The earthquake and

tsunami inflicted catastrophic damages on the country: a human toll of 15,858

dead, 3,021missing, and 6,080 injured (as of May 9, 2012); and a structural toll

of 129,855 total-loss buildings and 257,739 half-loss buildings. The estimated

damage caused by the disaster was enormous: approximately 16.9 trillion yen

as to buildings, industrial infrastructure in the agricultural and fishery sectors,

social infrastructure, and utilities. Ruinous damages spread to every corner of

the socioeconomic structure in the affected area [7]. The Great East Japan

Earthquake left behind a vast amount of disaster waste and Tsunami deposit in

13 prefectures of eastern Japan. Coastal cities and other municipalities in Iwate,

Miyagi, and Fukushima were particularly affected, left with approximately

3.78 million tons of disaster waste in Iwate, 10.46 million tons in Miyagi, and

1.73 million tons in Fukushima. These figures are equivalent to 8 years of mu-

nicipal solid waste in Iwate, 13 years in Miyagi, and 2 years in Fukushima [8].

Further, in the severe accident that occurred at the Tokyo Electric Power Com-

pany (TEPCO) Fukushima Daiichi Nuclear Power Station (NPS) following the

earthquake, a vast amount of radioactive material was discharged into the envi-

ronment [2].

Radioactive substances released into the atmosphere and water, irradiating a

large amount of debris from collapsed structures in area near Fukushima Nu-

clear Power Plant. Moreover, it is also estimated that concrete waste from the


13

collapsed reactor building as well as other structures and pavement needed to

be demolished after the plant settle down are enormous. The Tokyo Electric

Power Company reported that the major radioactive particles discharged were

radioactive iodine and cesium. It was estimated that the highest radioactive dis-

charge occurred on March 15 with about 800 trillion Bq of radioactive cesium

discharged per hour [9]. Cs-137 is the most concern radio isotope for Depart-

ment of Energy (DOE) environmental management sites. It has a half-life of 30

years. Cesium-137 presents an external as well as internal health hazard. While

in the body, cesium poses a health hazard from both beta and gamma radiation,

and the main health concern is associated with the increased likelihood for in-

ducing cancer [10].

2.3.1. Decontamination Method

The treatment and disposal of contaminated concrete are major issues for

all decommissioning project due to the very large quantities of material which

may be involved. The selection and usage of different dismantling and decon-

tamination techniques can significantly influence the total amount of contami-

nated material that need to be managed. In the concrete, the contamination de-

pends on the location and the history of the material, the contamination depth

can be a few millimeters to several centimeters [11]. Surface decontamination

is the most common decontamination method in nuclear plant decommission

before dismantling. In the event that a surface removal technique is first used to

separate the contaminated concrete, the volume of material waste could be sig-

nificantly reduced, though care should be needed in the case of possible non-

superficial contamination along cracks and in pipe penetrations [12].

Decontamination efforts in areas around Fukushima have been conducted

primarily in public facilities. A number of surface decontamination such as cut-


14

ting and stripping, washing, and blasting has been done to reduce the level of

radiation [13]. However, the massive earthquake and tsunami that hit Fukushi-

ma Daiichi Nuclear Plant has led to explosion which spread high level of radi-

oactivity, and thus surface decontamination were impossible.

2.3.2. Regulation for Disposal of Radioactive Waste

The volumetric clearance level of Cs-137 is 1000Bq/kg to be handled as

conventional industrial waste. According to the Ministry of Environment Re-

port on December 27th

, 2011, concrete waste with less than 3000 Bq/kg can be

reused at construction which deeper than 30 cm. Further, the typical radioac-

tive level of waste in Fukushima was 6460 Bq/kg. Therefore it required to be

decontaminated. While radioactive waste with cesium levels below 8,000

Bq/kg can be managed as underground disposal. Due to large quantity of con-

taminated concrete waste, an effective decontamination method is needed.

2.4. Recycled Aggregate from Concrete Waste

In worldwide, 26 billion tons of materials were processed each year,

including 20 billion tons of stone, gravel, and sand used for road building and

construction [14]. Indeed, the increased demand for concrete leads to

resources-depletion problems. In the other hand the demolition of old and

deteriorated buildings is inevitable. The main reasons for this situation are

changes of purpose, structural deterioration, rearrangement of a city, expansion

of traffic directions and increasing traffic load, natural disasters (earthquake,

fire and flood), etc. [15]. Therefore, to reduce the use of natural resources and

the amount of concrete waste as a result of demolition of old building, the

utilization of recycled aggregate is a key issue.


15

Recycled aggregates are produced from the re-processing of mineral waste

materials, with the largest source being construction and demolition waste.

Construction and demolition waste are normally composed of concrete rubble,

bricks and tiles, sand and dust, timber, plastics, cardboard and paper, and metal.

Concrete rubble usually constitutes the largest proportion of construction and

demolition waste [16].

2.4.1. Utilization of Recycled Aggregate

In 1991, the Japanese government established the Recycling Law. It

required relevant ministries to nominate materials to control and encourage the

reuse and recycling of those materials under their responsibility. The former

Ministry of Construction (MOC) nominated demolished concrete, soil, asphalt

concrete, and wood as construction by-products. The MOC presented the

“Recycle 21” program in 1992, which specifies numerical targets for recycling

of several kinds of construction by-products. The target for the recycling ratio

of demolished concrete in the year 2000 was 90 percent, and the actual results

for 1990, 1993 and 1995 were 48 percent, 67 percent and 65 percent,

respectively. In 2000 it reached 96%, but almost entirely as a sub-base material

for road pavement [17].

Some key benefits of recycling concrete include [18] :

- Reduction of waste, landfill or dumping and associated site degradation

- Substitution for virgin resources and reduction in associated

environmental costs of natural resource exploitation

- Reduced transportation costs: concrete can often be recycled on

demolition or construction sites or close to urban areas where it will be

reused

- Reduced disposal costs as landfill taxes and tip fees can be avoided


16

- Good performance for some applications due to good compaction and

density properties (for example, as road sub-base)

- In some instances, employment opportunities arise in the recycling

industry that would not otherwise exist in other sectors.

Although it provides many benefits especially to preserve natural resources

and reduce the amount of concrete waste which need to be disposed, the

utilization of recycled aggregate is still limited. The limitation of using

recycled aggregate is affected by lack of suitable laws, low quality of recycled

aggregate, lack of code and specifications, many variation in recycled

aggregate quality, cost amounts of by-products, poor image of recycled

aggregate, inefficient supply system and lack of experience [17].

2.4.2. Properties of Recycled Aggregate

It is well known that recycled aggregate has lower quality compared to

natural aggregate. Because recycled aggregate contains mortar from the

original concrete, it is more porous and absorptive than natural aggregates. It is

reported that recycled coarse aggregate had water absorption of 5% to 6%,

while recycled fine aggregate absorption was 9% to 10%. These properties are

significant compared to natural aggregate which typically has absorption of 1%

to 2% [19].

2.4.3. Specification of Recycled Aggregate

As the use of recycled aggregate is very important to save natural resources,

nevertheless the use of recycled aggregates is still limited due to very varied

quality of recycled aggregate, therefore, standard and rules which provide

guidance are necessary to encourage the utilization of recycled aggregates. In


17

Japan, the following three standards have been established concerning recycled

aggregate [1] :

JIS A 5021-Recycled aggregate for concrete –Class H

JIS A 5022 – Recycled concrete using recycled aggregate – Class M

JIS A 5023 – Recycled concrete using recycled aggregate – Class L

Table 2.1 shows definitions regarding oven-dry density and water

absorption ratio of recycled aggregate under JIS classification.

Table 2.1 Definitions regarding oven-dry density and water absorption ratio

of recycled

Class H Class M Class L

Coarse Fine Coarse Fine Coarse Fine

Oven-dry density

(g/cm3)

2.5 2.5 2.3 2.2 - -

Water absorption

(%) 3.0 3.5 5.0 7.0 7.0 13.0

2.4.4. Properties of Recycled Aggregate Concrete

Many studies on the use of recycled aggregate in concrete production have

been attempted. It is well reported that recycled aggregate concrete has lower

quality compared to natural aggregate concrete in strength and durability,

therefore the use of recycled aggregate is limited and mainly used for non-

structural concrete.

Applications of recycled concrete are generally limited to the members or

positions that do not require higher strength or higher durability [20]. As the

replacement ratio increases, the compressive strength and elastic modulus

decreases [21,22,23]. With 100% recycled aggregate, the modulus of elasticity

of the concrete was about 35% lower than the modulus of the reference


18

concrete [19]. Concrete made with 100% of recycled coarse aggregates has 20–

25% less compressive strength than conventional concrete at 28 days, and

requires high amount of cement to achieve a high compressive strength and

consequently is not an economic proposition as it is not cost effective. These

recycled aggregates should be used in concretes with low–medium

compressive strength [24].

It is reported that drying shrinkage and creep of concrete are significantly

increased by the use of recycled aggregate and, in particular, fine aggregate.

After 2 years, the drying shrinkage of concrete made with 100% recycled

aggregate was 60% to 100% greater than the reference concrete. Creep was up

to 350% higher [19]. Due to its poor quality, recycled aggregate is mainly

confined to low-grade applications [25].

2.5. Fly Ash

Besides slag cement, fly ash is the most common supplementary cementi-

tious material used in concrete. Fly ash is a coal combustion by-product in

coal-fired power plant. The main environmental benefit of using fly ash instead

of conventional cement is reducing greenhouse gas emissions and the need of

landfill. For every ton of fly ash used for a ton of portland cement (the most

common type of cement in general use around the world) approximately one

ton of carbon dioxide is prevented from entering the earth’s atmosphere [26].

2.5.1. Composition of Fly Ash

In Japan, 90% or more of the coal ash generated is from pulverized coal

combustion, dwarfing the 7% or so from fluidized-bed and some 1-2% from

stoker combustion. The generation ratio of fly ash to clinker ash (bottom ash) is


19

9:1 [27]. The average grain size of fly ash from pulverized coal combustion is

approximately 25 m, similar to silt in fineness, between finer clay and coarser

fine-grained sand for use as a soil material [27]. The chemical composition re-

sembles mountain soil, with two inorganic components, silica (SiO2) and alu-

mina (Al2O3) comprising 70-80% of the total composition. Other than these,

ferric oxide (Fe2O3), magnesium oxide (MgO), and calcium oxide (CaO) are

also contained in slight amounts [27].

2.5.2. Utilization of Fly Ash in Concrete

According to a survey conducted by the Center for Coal Utilization in 2003,

the coal ash generation rate in Japan was 9.87 million tons a year, up 6.8%, or

630,000 tons, from the preceding year [27]. Fig. 2.4 shows changes in the rate

of coal ash utilization and generation from electric power utilities and One-

MW or larger installed power generation plants in general industries from 1993

through 2003 [27]. This number is expected to continue growing, especially

after the Great East Japan Earthquake, which caused the termination of a num-

ber of nuclear power plant in Japan, and encourage new construction of coal-

fired power plant to meet electricity demand.

For using in construction, fly ash is classified into three groups: low tech-

nology applications; medium technology applications; and, high technology

applications. The low technology applications include the use of fly ash in fills

and embankments, pavement and sub-base courses, subgrade stabilizations,

landfill cover, soil improvement, land reclamation, slurried flowable ash, and

water pollution control. The medium technology applications include the utili-

zation of fly ash in blended cements, lightweight aggregates, various types of

concrete, precast/prestressed products, bricks, blocks, paving stones, artificial

reefs, etc. The high technology applications involve the use of fly ash as a raw


20

material for metal recovery, filler for metal matrix composites, polymer matrix

composites, and several other filler applications [28].

Fig. 2.4 Changes in coal ash generation and utilization rates [27]

In Japan, following its commercialization as a cement admixture early in

the 1950’s, standards were established for fly ash in 1958 and then for fly ash

cement in 1960, encouraging its widespread application in general concrete

structures. By 2003, 70.1% of all the effectively used fly ash was used as clay-

alternative raw material and Japanese Industrial Standards (JIS) specify stand-

ards for fly ash cement, allowing the mixture to range from 5-30% [27].

2.5.3. Specification of Fly Ash

Specifications and guidance for use of fly ash are different in several coun-

tries. ASTM C-618 categorizes coal combustion fly ash into two classes: Class

F and Class C. The Class F fly ashes are normally generated due to combustion


21

of anthracite or bituminous coal. The Class C fly ashes are produced due to

burning of lignite or sub-butiminous coal. ASTM Class C fly ashes (high-lime

fly ashes) typically contain CaO in excess of 10% up to 40%, and Class F fly

ashes (low-lime fly ashes) generally contain less than 10% CaO. Due to high

CaO content, Class C fly ashes participate in both cementitious and pozzolanic

reactions whereas Class F fly ashes predominately participate in pozzolanic

reaction during the hydration process. Therefore, Class C fly ashes are classi-

fied as cementitious and pozzolanic admixtures/additives and Class F fly ashes

as normal pozzolans for use in concrete [28].

In Japan, the specification of fly ash is regulated by Japan Industrial Stand-

ard (JIS) A 6201. Fly ash is classified into four classes as given in Table 2.2.

Table 2.2 Quality of fly ash (JIS A 6201)

Notes: 1. In place of ignition loss, the unburned carbon content ratio may be measured

by the method specified in JIS M 8819 or JIS R 1603 to apply to the result a

stipulated value of ignition loss.

2. Fineness based on the screen sieve method or the Blaine method.

3. Regarding fineness, the results of the Blaine method are provided as a refer-

ence value for the screen sieve method.


22

2.5.4. Properties of Fly Ash Concrete

The utilization of fly ash in concrete has been widely reported. Oner A et al.

reported that the optimum value of fly ash is about 40% of cement. Fly ash-to-

cement ratio is an important factor determining the efficiency of fly ash [29].

While the compressive strength of fly ash concrete increases by adjustment in

w/b ratio, the durability of concrete is improved by the use of fly ash [30]. Fur-

thermore, when fly ash concrete used for real concrete structure in salt laden

environment, it demonstrates reduction of chloride penetration [31].

In the recommendation of using fly ash published by Japan Society of Civil

Engineers (JSCE), it is reported that the strength development of concrete contain-

ing fly ash is strongly affected by the type and replacement ratio of fly ash and

curing conditions. Concrete strength generally decreases at early ages as the fly

ash replacement ratio increases, but higher strength can be achieved in older age of

concrete. In addition, drying shrinkage of concrete containing fly ash is generally

smaller than that of concrete without fly ash [32].

2.6. Pulsed Power Technology to Produce High Quality Recy-

cled Aggregate

2.6.1. Procedures of Reclaiming Aggregate by Pulsed Power

Technology

Pulsed power discharge is a technique that spatially and temporally com-

presses and superimposes stored energy, thereby concentrating, controlling, and

transmitting a large amount of power within a small space, although for only a

short period of time [33]. Pulsed power technique has been developed to repro-

duce a high quality recycled aggregate from concrete waste. Recycled aggregate


23

can be reclaimed by applying pulsed power to concrete specimens immersed in

water. Fig. 2.5 illustrates the process of crushing the concrete waste by pulsed

power discharge method, while Fig. 2.6 illustrates concrete waste discharged by

pulsed power technique.

Fig. 2.5 Process of crushing the concrete waste by pulsed power technique

Fig. 2.6 Concrete waste was discharged by pulsed power

In this method, concrete waste is placed on the hemisphere mesh of 5mm as

ground voltage electrode and struck by pulsed high voltage electric current dis-

charged from high voltage electrode. This technology crushes the concrete by

dielectric breakdown of gas. The gas in the concrete becomes plasma when

pulsed electrical discharges are generated inside of concrete, because the dielec-

tric breakdown level of the gas is lower than liquid and solid. Therefore, the

cracks occur principally in the interfacial transition zone along each aggregate

particle. The shock wave is generated by the rapid volumetric expansion of

plasma at the same time. The shock wave propagates in concrete. The shock

wave is divided into reflected wave and penetration wave at the boundary of


24

coarse aggregate and mortar. The penetration wave and reflected wave gener-

ates tensile stress which delaminates mortar from aggregate. After several repe-

titions of discharge, it generates recycled aggregate that completely separated

from the mortar [6]. The discharge pass in concrete is shown in Fig 2.7.

Fig. 2.7 Discharge pass in concrete [34]

2.6.2. Properties of Recycled Aggregate produced by Pulsed

Power Technology

Previous research has found that coarse aggregate reproduces by discharged

energy of 640 kJ has sufficient quality to satisfy JIS (Japan Industrial Standard)

regulation class H (A5021) [6,35,36]. In addition to the density and absorption

of aggregate, concrete made of recycled coarse aggregate also has sufficient

compressive strength and Young’s Modulus for use as construction materials.

Conditions of reclaimed aggregate depend on the number of pulsed power

shots as shown in Fig 2.8. After 100 shots with total discharged energy of 640

kJ, coarse aggregate reclaimed is fully separated from mortar. Fig. 2.9 illustrates


25

reclaimed materials by the pulse power discharge, which are separated into

coarse aggregate, fine aggregate and powders.

Fig. 2.8 Relations between reclaimed coarse aggregate and number of

pulsed power shots [37]

Fig. 2.9 Reclaimed materials by pulsed power discharge


26

Bibliography

1. Sakai K, Noguchi T, “Sustainable Use of Concrete“, CRC Press, Taylor

and Francis Group, Boca Raton, 2012

2. Cembureau, “Activity Report 2012”, 2012

3. Noguchi T, “Resource Recycling in Concrete: Present and Future”, Stock

Management for Sustainable Urban Generation, Springer, Ch. 13, 2009

4. World Business Council for Sustainable Development and International

Energy Agency,” Cement Technology Roadmap 2009 : Carbon emissions

reduction up to 2050”, 2009

5. Marinkovic S, Ignjatovic I, “Recycled aggregate concrete for structural use

- an overview of technologies, properties, and applications”, ACES Work-

shop, Innovative Materials and Techniques in Concrete Construction, Cor-

fu, October 10-12, 2010



2010, www.ct-si.org, ISBN 978-1-4398-3419-0,2010

7. Ministry of the Environment Government of Japan, “Response to the Great

East Japan Earthquake and Nuclear Power Station Accidents”, Annual Re-

port on the Environment, the Sound Material-Cycle Society and the Biodi-

versity in Japan 2012, Ch. 2, 2012



27

8. Ministry of the Environment, “Disposal of Disaster Waste”, Annual Re-

port of the Environment, The Sound Material-Cycle Society, and Biodi-

versity in Japan, 2013

9. Wada K, Yoshikawa T, Murata M, “Decontamination Work in the Area

Surrounding Fukushima Dai-ichi Nuclear Power Plant : Another Occupa-

tional Health Challenge of Nuclear Disaster”, Archive of Environmental &

Occupational Health, 67:3, pp. 128-132, 31 July 2012

10. Environmental Science Division, “Cesium”, Human Health Fact Sheet,

Argonne National Laboratory, August 2005

11. Lawrence E. Boing, “Decommissioning of Nuclear Facilities, Decontami-

nation Technologies”, International Atomic Energy Agency, Manila, Phil-

ippines, October 2006.

12. Radioactive Waste Management Committee, “The NEA CO-Operative

Programme On Decommissioning Decontamination and Demolition of

Concrete Structures”, Organization for Economic Co-operation and De-

velopment, Nuclear Energy Agency, NEA/RWM/R(2011)1, 20 September

2011.

13. Shiratori Y, Tagawa A, “FY 2011, Decontamination Technology Demon-

stration Test Project ”, Japan Atomic Energy Agency, 2012

14. Brown LR, “Eco-Economy: Building an Economy for the Earth”, W. W.

Norton & Co., NY, 2001

15. Malešev M, Radonjanin V, Marinković S, “ Recycled Concrete as Aggre-

gate for Structural Concrete Production”, Sustainability Journal, Vol 2,

2010, pp. 1204-1225, ISSN 2071-1050

16. Kou S, “ Reusing Recycled Aggregates in Structural Concrete”, PhD thesis,

The Hong Kong Polytechnic University, 2006

17. Kawano H, “The State of Using By-product in Concrete in Japan and Out-

line of JIS/TR on ‘Recycled concrete using recycled aggregate’”, Public


28

Works Research Institute, JAPAN, Proceeding of the 1st Fib congress,

2002

18. World Business Council for Sustainable Development, “The Cement Sus-

tainability Initiative : Recycling Concrete”, July, 2009

19. McGovern M, “Recycled aggregate for reinforced concrete”, July 2002

Vol. 23, No. 2 Concrete Technology today, PCA (Portland Cement Asso-

ciation).

20. Tsuji Y, Suzuki Y, ”Japanese Standardization of Recycling materials to

concrete”, 27th

Conference on Our World in Concrete & Structures : 29 –

30 August 2002, CI-Premier PTE LTD, Singapore

21. Eguchi K, Teranishi K, Nakagome A, Kishimoto H, Shinozaki K, Nari-

kawa M, “Application of recycled coarse aggregate by mixture to concrete

construction”, Construction and Building Materials Journal, Vol. 21, 2007,

pp. 1542-1551)

22. Xiao J, Li J, Zhang Ch, “Mechanical properties of recycled aggregate con-

crete under uniaxial loading”, Cement and Concrete Research Journal, Vol.

35, 2005, pp. 1187-1194

23. Tabsh SW, Abdelfatah AS, “ Influence of recycled concrete aggregates on

strength properties of concrete”, Construction and Building Materials

Journal, Vol. 23, 2009, pp. 1163-1167)

24. Etxeberria M, Vazquez E, Mari A, Barra M, “Influence of amount of recy-

cled coarse aggregates and production process on properties of recycled

aggregate concrete”, Cement and Concrete Research Journal, Vol. 37,

2007, pp. 735-742

25. Tam WYV, Tam CM, Wang Y, “Optimization on proportion for recycled

aggregate in concrete using two-stage mixing approach”, Construction and

Building Materials Journal, Vol. 21, 2007, pp. 1928-1939


29

26. Speight JG, “Power generation, coal-fired power generation handbook”,

John Wiley & Sons, Inc. and Scrivener Publishing LLC, Canada, 2013

27. Japan Coal Energy Center, “Clean coal technologies in Japan, technology

innovation in the coal industry”, January, 2007

28. Naik TR, Singh SS, “Fly Ash Generation and Utilization-an overview”,

Recent Trend in Fly Ash Utilization, June, 1993

29. Oner A, Akyuz S, Yildiz R, “ An experimental study on strength develop-

ment of concrete containing fly ash and optimum usage of fly ash in con-

crete”, Cement and Concrete Research, Vol. 35, 2005, pp. 1165-1171

30. Nath P, Sarker P, “Effect of Fly Ash on the Durability Properties of High

Strength Concrete”, Procedia Engineering, Vol. 4, 2011, pp. 1149-1156


Third International Conference on Sustainable Construction Materials and


32. JSCE Research Committee on Fly Ash for Use in Concrete, “Recommenda-

tion for Construction of Concrete Containing Fly Ash as Mineral admixture”,

Concrete Library of JSCE No 36, December 2000

33. Akiyama, H. (2003). High-Voltage Pulsed Power Engineering. Ohmu-sha.

Tokyo. pp. 1-2. pp. 36-38. p. 95.

34. Namihira T, Wang D, Akiyama H, “ Pulsed Power Technology for Pollu-

tion Control”, Proceedings on the 2nd

Euro-Asian Pulsed Power Confer-

ence, Acta Physica Polonica A, Vol 115, 2009, pp. 953-955



cled coarse aggregates by pulsed power discharged”, 1-4244-0914-4/07,

2007 IEEE., Kumamoto University, 2007

36. Japanese Standard Association, JIS A 5021 “Recycled Aggregate for Con-

crete-Class H”, 2005


30

37. Kencanawati NN, “Acoustic Emission Weibull Analysis for Reliability

Evaluation of Deteriorated Concrete and Recycled Aggregate Concrete”,

Doctor of Philosophy Thesis, Kumamoto University, 2011

31

CHAPTER 3

Application 1 : Reduction of Radioactive Con-

taminated Concrete by Pulsed Power Discharged

3.1. Introduction

Catastrophic disaster of the Fukushima Dai-ichi Nuclear Power Plant in

2011 resulted in irradiating a large amount of radioactive substances in atmos-

phere and water, and remaining a huge amount of debris from collapsed struc-

tures in the area near the plant. At present, an enormous amount of concrete

waste from the reactor buildings collapsed, associated structures and pave-

ments need to be safely disposed. Recently, the utilization of recycled materials

has long been developed in Japan, including recycled aggregate in concrete. It

has been reported that the recycling ratio of waste concrete scraps in Japan has

been kept over 98% since 2006 [1]. Consequently, research concerned the con-

crete waste should be intensively studied for recycling radioactive concrete

waste from Fukushima nuclear plants.

The decommission of nuclear power plants conventionally has leaded to the

major issue on treatment and disposal of large amount of contaminated con-

crete. Methodologies and practices for dismantlement and decontamination of

contaminated concrete to be processed are significantly associated with safety,

CHAPTER 3 Reduction of Radioactive Contaminated Concrete by Pulsed Power

Discharged

32

cost and duration. It has been reported that concrete the depth of contamination

varies from a few millimeters to several centimeters [2]. Prior to dismantling,

surface decontamination is the most common method in nuclear plants. This is

because the contamination is normally limited on the surface of concrete, thus

surface removal techniques are first applied to dismantle contaminated con-

crete. However, to minimize the possibility of non-superficial contamination

along cracks and pipelines, care is needed [3,4].

Fukushima Dai-ichi Nuclear Power Plant has suffered from the spread of

radioactive substances in the air and water when huge earthquake and tsunami

hit eastern Japan. Large amounts of concrete structures were contaminated in

the area nearby, and thus the surface decontamination is not only impractical

but also in applicable. A more effective decontamination technique is required

to address this issue.

In the present paper, a decontamination method for safe removal of radio

isotope cesium (Cs) from contaminated concrete waste is studied. Cs is known

as a longest-lived radioisotope which decays by emitting a beta particle for Cs-

137 with a half-life of 30 years and Cs-134 with a half-life of 2 years. In the

human body, Cs poses a health hazard due to both beta and gamma radiation,

inducing serious damages [5]. Cs-134 and Cs-137 are the most radioactive ma-

terials found in Fukushima, and high concentration of those was detected in

areas near the Fukushima Dai-ichi Nuclear Power Plant. Table 3.1 shows radi-

oactive Cs contents of debris irradiated from the power plant buildings. Since

these require special handling, an effective way to decontaminate the radio iso-

tope Cs from concrete waste has to be developed.

Considering the vast amount of contaminated concrete waste, an effective

decontamination is needed. In this study, pulsed power technology is proposed

as decontamination method to reduce the volume of contaminated concrete

waste by reclaiming aggregate from contaminated concrete waste.


Discharged

33

Table 3.1 Radioactive Cs Contents of Debris [6]

Fabric Moisture Content

(%)

Radioactive Cs Content

(Bq/kg-wet)

Otani-Stone 6.0 30 600

Cement Brick 3.6 6 460

Slate Roof Tile 1.2 6 550

Timber 9.1 7 550

Galvanized Iron 0.0 9 530

Plaster Board 18.2 256

Ceramics Roof Tile 1.6 1 269

PVC Pipe 0.5 13 850

3.2. Objectives

This study has the following objectives:

a. To propose pulsed power discharge as decontamination method in order

to reduce the volume of radioactive concrete waste.

b. Evaluation of the effectiveness of pulsed power discharge to decontam-

inate radioactive concrete waste.

3.3. Contaminated Concrete

Reducing concrete waste can be performed by applying the technology for

recycling coarse aggregate. In the case of contaminated concrete, coarse aggre-

gate is unlikely to be heavily contaminated. It is well known that radioactive Cs

is adsorbed into clay materials. Therefore, Cs might exist predominantly in ma-

trix of concrete where the C-S-H composite is similar to clay. It is expected

that watertight coarse aggregate would not contain radioactive Cs.

Min et.al has reported that the radionuclide is concentrated mainly in the

porous cement paste, and that gravel and sand aggregates have reasonably low-

activity concentrations [7,8]. Fig. 3.1 illustrates the scheme of contaminated


Discharged

34

concrete waste. As the contamination is mainly concentrated in the cement

paste, therefore, reclaimed coarse aggregate from contaminated concrete could

be recycled in concrete [9].

Fig 3.1 Scheme of Contaminated Concrete Waste [8]

Our basic concept for reducing contaminated concrete waste is to separate

aggregate, which ranges between 60% - 80% in the total volume of concrete. It

has been reported that the amount of recycled coarse aggregate reclaimed by

the pulsed power discharged is around 50% of the total volume of concrete [1].

3.4. Pulsed Power Technology to Reduce Contaminated Con-

crete Waste

Separating and recovering high-quality uncontaminated recycled coarse

aggregate from contaminated concrete waste is investigated by using the pulsed


Discharged

35

power discharge technique. Previous research shows that high-quality recycled

coarse aggregate can be separated and recovered by the technique

[1,10,11,13,14].

The energy per pulsed power discharge is varied by changing the

capacitance of the capacitors and the generated voltage of the pulsed power

generator. Concerning ordinary concrete, the optimal processing parameters

were investigated in terms of the oven-dry density and water absorption

coefficient of the recycled coarse aggregate [1,10]. As a technology for

reclaiming aggregate from concrete waste, that is completely different from

other methods based on mechanical disruption and recovery from concrete, the

pulsed power can delaminate the mortar interface from coarse aggregate. Since

radioactive substances mainly penetrate into cement and mortar matrix, the

volume of radioactive contaminated waste can be reduced by reclaiming

aggregate from contaminated concrete.

To reduce contaminated waste by reclaiming aggregate from contaminated

concrete waste, pulsed power discharge is applied. Crushing the imitation of

radioactive contaminated concrete specimens to reclaim aggregate was carried

out by the pulsed power discharge in water, and then the Cs distribution of

coarse aggregate, fine aggregate and the powder were analyzed.

3.5. Experiment

3.5.1. Material Used

Ordinary Portland cement with density of 3.16 g/cm3 was used to make

concrete specimens. Natural crushed limestone sand and gravel were used.

Limestone aggregate was selected because this type of aggregate is soluble in

acid which used in the distribution analysis of Cs process. Physical properties


Discharged

36

of aggregates used in the experiment are shown in Table 3.2.

Table 3.2 Properties of aggregate for specimens

Oven-dry Density

[saturated surface-dried]

(g/sm3)

Water Absorption

Coefficient (%)

Coarse Aggregate

(Crushed lime stone) 2.71 0.57

Fine Aggregate

(Milled lime stone) 2.66 1.65

3.5.2. Mixture Proportion

Cube specimens of dimension with dimension of 100mm x 100mm x

100mm were made. Mixture proportion is listed in Table 3.3. The specimens

were cured in water for 28 days after casting, and dried for one week at 105

5oC in a dried oven to vaporize moisture from inside concrete and obtain a

constant mass.

Table 3.3 Mixture proportion for concrete specimens

Maximum

aggregate

size (mm)

Water-to-

Cement

ratio

(%)

Sand-to-

Gravel

ratio (%)

Water

(kg/m3)

Cement

(kg/m3)

Sand

(kg/m3)

Gravel

(kg/m3)

20 55 48 175 318 882 943

3.5.3. Contaminated Concrete Simulation

As the first step, the stable isotope 133

Cs was applied to simulate radioactive

contaminated concrete, in order to verify an effectiveness of the pulsed power


Discharged

37

discharge as a decontamination method. The imitation of contaminated

concrete by Cs was made by immersing the specimens into aqueous solution of

0.1M of cesium chloride CsCl for one month.

3.5.4. Cs Penetration into Concrete Specimen

After immersion of the specimens, the specimens were cut into a cube of

dimensions of 0.5 mm in all directions for EPMA (Electron Probe Micro

Analysis) mapping.

3.5.5. Cs Penetration into Concrete Specimen

Coarse aggregate was reclaimed by the pulsed power discharged under

water. The concrete specimen was placed in a hemispherical stainless steel

mesh. A polyethylene-coated copper wire of 5 mm in diameter was used as the

high-voltage electrode, with the bottom end of the electrode fixed in contact

with the specimen. During discharge, the stainless steel hemispherical mesh

was connected to ground and serves as the low-voltage electrode.

Each specimen was subjected into two discharged steps. At the first step,

200 shots at 6.4 kJ were applied with a 5 mm mesh opening for a total amount

of energy equivalent to 1280kJ. Aggregate smaller than 5 mm was subjected to

the second discharged of 300 shots at 3.6 kJ with a 1.2 mm mesh opening for a

total amount of energy equivalent to 1080 kJ.

3.5.6. Cs Distribution Analysis for the Reclaimed Aggregate

ICP-MS (Inductively Coupled Plasma Mass Spectroscopy) analysis was

conducted to identify the distribution of Cs in reclaimed aggregate and the


Discharged

38

treated water. ICP-MS enables to analyze both solid and liquid materials

dissolved. Samples tested were first dissolved by acid solution. Limestone was

selected since it can be dissolved in acid solution.

3.6. Result and Discussion

3.6.1. Quantity and Quality of Reclaimed Aggregate

The average mass of the specimens was 2.46 kg. The mass ratio of

aggregate used in producing concrete is 79%, and 60% of its aggregate was

reclaimed using the pulsed power discharge. Reclaimed aggregate was

obtained by 5 mm and 1.2 mm mesh opening in the first and second step of

pulsed power discharge, respectively. The water absorption of reclaimed

aggregate was 1.74%, while that of original aggregate was 0.57%. The value of

reclaimed aggregate is satisfied the water absorption prescribed in Japan

Industrial Standard for high quality recycled aggregate for concrete Class H

(JIS A 5201) as lower than 3%. It is found that the volume of the radioactive

concrete was reduced up to 60%. Recycled aggregates obtained by the pulsed

power technology are shown in Fig 3.2. Aggregate is found to be completely

separated from the mortar.

(a) (b) (c)

Fig 3.2 Reclaimed aggregates on the mesh electrode; (a) coarse aggregate; (b)

fine aggregate larger than 2.5 mm; (c) fine aggregate smaller than 2.5 mm


Discharged

39

3.6.2. Cs Distribution Result

The distribution analysis of Cs was performed twice; before and after

crushing the specimens by the pulsed power technique. The EPMA (Electron

Probe Micro Analysis) was conducted after immersion of the specimens into

CsCl solution, before crushing the specimens, to investigate the penetration of

Cs in concrete.

(a)

(b)

Fig 3.3 (a) Location of cut sample for EPMA (Electron Probe Micro Analysis)

(b) The result of EPMA for relative intensity of Cs-Kα


Discharged

40

The result showed that Cs concentration was high on the surface of the

concrete and low in the interior of the concrete blocks. In addition, although Cs

penetration was not found in the aggregate, Cs concentration was slightly

higher at the boundary between aggregate and cement hydrates. The result of

EPMA for distribution of Cs is shown in Fig 3.3.

ICP-MS analysis was conducted after crushing the specimens by the pulsed

power discharge. Results of the distribution of Cs by the ICP-MS analysis are

listed in Table 3.4.

Table 3.4 Distribution of Cs in reclaimed materials by ICP-MS

Sample

Reclaimed

Aggregate

from 5 mm

wire mesh

electrode

Reclaimed

Aggregate

from 1.2 mm

wire mesh

electrode

Residue

Treated water

(containing

cement particles)

Distribution

of Cs 0.3% 2.7% 2.5% 94.5%

As shown in Table 3.4, only 0.3% of Cs is detected in reclaimed coarse

aggregate which was collected by the 5mm wire mesh electrode. In contrast,

the distribution of Cs in reclaimed fine aggregate obtained from 1.2 mm wire

mesh is 2.7 %. The distribution of Cs in the residue retained from 0.55m sieve

which could contain cement paste lumps and fine mortar is 2.5%. The

distribution of Cs in reclaimed materials by the pulse power discharge shows

that coarse aggregate from contaminated concrete is almost uncontaminated.

Cs was mainly dissolved in water used in pulse power process, which

contained many cement particles with the ratio of 94.5%.

Concentration of Cs used in this research was 0.1 M CsCl, which is a very

high concentration compared to contaminated water sample in Fukushima Dai-

ichi Nuclear Power Plant. It is reported that radioactive contaminated water at


Discharged

41

the site was 2.5x106 Bq/ml and 2.9x10

6 Bq/ml for Cs-134 and Cs-137,

respectively. The concentration of 0.1M CsCl used in the experiment is

comparable to 5.387x1016

Bq/ml. This amount shows a huge difference in the

concentration of Cs between tested in the experiment and observed at the site.

The used of high concentration of Cs in the experiment was prepared to ensure

that the detection is enabled in the analysis. Therefore, it is confirmed that high

concentration of Cs, which has not been adsorbed by cement matrix but filled

concrete pores was dissolved in the water during the crushing process using

pulsed power discharge.

3.6.3. Discussion on Japan Government Regulation for Radio-

active Waste Disposal

According to Japan regulation on radioactive waste, the clearance level of

radioactivity is 1000 Bq/kg to be handled as conventional industrial waste.

Since reclaimed coarse aggregate by pulsed power discharge was

predominantly uncontaminated, it is expected that the radioactivity level of

recycled coarse aggregate reclaimed from contaminated concrete waste could

be lower than the clearance level and can be readily reused.

On December 27th

, 2011, Ministry of Environment Report announced that

concrete waste with radioactivity level lower than 3000 Bq/kg can be reused

for construction deeper than 30 cm from the ground level, while radioactive

waste with cesium levels below 8,000 Bq/kg can be managed as underground

disposal. It is reported that typical radioactivity level of waste in Fukushima is

6460 Bq/kg and required to be decontaminated. Due to large quantity of

contaminated concrete waste to be disposed, an effective decontamination

method is needed. The pulsed power is expected to be an effective

decontamination method, particularly in reducing the volume of radioactive


Discharged

42

contaminated concrete waste.

3.7. Conclusion

A method for aggregate recycle process for contaminated concrete is studied

to reclaim high quality aggregate. Because the proposed method can separate

aggregate and contaminated cement matrix, it is found to be promising for the

decontamination of radioactive contaminated concrete waste.

The effectiveness of the pulsed power discharge to reduce the volume of

contaminated concrete waste by recycling aggregate is clarified. Following

conclusions can be derived from this research:

1. The pulsed power discharge can be applied as a decontamination method to

the radioactive contaminated concrete and is found to reduce the volume of

radioactive concrete waste up to 60%.

2. Coarse aggregate reclaimed from contaminated concrete waste was predom-

inantly uncontaminated. Therefore it could be reused as recycled aggregate.

3. Almost 95% of Cs was dissolved in the treated water in the pulsed power

process. Consequently, decontamination of the treated water used in the

pulsed power process is necessary.

However, high concentration of cesium solution was used in this simulation.

Therefore, it is necessary to reevaluate the elution of Cs to water under a condi-

tion equivalent to the actual radioactive contaminated concrete.


Discharged

43

Bibliography



2010, www.ct-si.org, ISBN 978-1-4398-3419-0,2010

2. L. E. Boing, “Decommissioning of Nuclear Facilities, Decontamination

Technologies”, International Atomic Energy Agency, Manila, Philippines,

October 2006

3. Radioactive Waste Management Committee, “The NEA CO-Operative

Programme On Decommissioning Decontamination and Demolition of

Concrete Structures”, Organization for Economic Co-operation and De-

velopment, Nuclear Energy Agency, NEA/RWM/R(2011)1, 20 September

2011.

4. P. O’Sullivan, J.G. Nokhamzon and E. Cantrel, “Decontamination and

Dismantling of Radioactive Concrete Structures”, NEA Updates, NEA

News No 28.2, p. 27-29, 2010

5. Anonym, “Cesium”, Human Health Fact Sheet, Idaho National Laboratory

Site, Environmental Surveillance, Education, and Research Program, ANL

October 2011

6. Center for Material Cycles and Waste Management Research, National

Institute for Environmental Studies, “Appropriate waste disposal judged

from radiological behavior”, December 2nd

, 2011, Japan. (In Japanese)



Discharged

44

7. B. Y. Min, W. K. Choi, K. W. Lee, “Volume Reduction of dismantled

concrete wastes generated from KRR-2 and UCP”, Nuclear Engineering

and Technology, Vol. 42, No. 2, April 2010.

8. B. Y. Min, W. K. Choi, K. W. Lee, “Separation of Clean Aggregates From

Contaminated Concrete Waste by Thermal and mechanical Treatment”,

Annals Of Nuclear Energy, Vol. 37, Page 16-21, Elsevier, November 2010

9. H. A. W. Cornelissen, “Volume Reduction of Contaminated Concrete”,

WM Symposia Proceeding, Page 1477-1479, 1993

10. S. Narahara, T. Namihira, K. Nakashima, S. Inoue, S. Iizasa, S. Maeda, M.

Shigeishi, M. Ohtsu and H. Akiyama, “Evaluation Of Concrete Made

From Recycled Coarse Aggregate by Pulse Power Discharge”, IEEE, 1-

4244-0914-4/07, 2007

11. M. Takaki, et al., "Managing the Quality of Coarse Aggregate Recovered

from Waste Concrete by Applying Electrical Discharge Shocks in Water."

Proceedings of the 2006 Conference of the West Branch of the Japan Soci-

ety of Civil Engineering, Kita-Kyushu, pp. 827-828., 2007 (In Japanese)

12. H. Akiyama, High-Voltage Pulsed Power Engineering, Ohmu-sha, Tokyo,

pp. 1-2. pp. 36-38. p. 95, 2003 (In Japanese)

13. S. Maeda, M. Shigeishi, T. Namihira, S. Iizasa, “Research on Concrete

Aggregate Collection Technology by Pulsed Power Discharge”, 34th

Con-

ference on Our World In Concrete & Structures, Singapore, 16-18 August

2009

14. S. Inoue, J. Araki, T. Aoki, S. Maeda, S. Iizasa, M. Takaki, D. Wang, T.

Namihira, M. Shigeishi, M. Ohtsu and H. Akiyama, “Coarse Aggregate

Recycling by Pulsed Discharge Inside Concrete”, Proceedings of the 2nd

Euro-Asian Pulsed Power Conference, Vilnius, Lithuania, September 22-

26, 2008


Discharged

45

15. Japanese Standard Association, JIS A 5021 “Recycled Aggregate for Con-

crete-Class H”, 2005

46

CHAPTER 4

Application 2 : Strength and Drying Shrinkage

of Concrete Made From Recycled Aggregate by

Pulsed Power Technology with Fly Ash as Ce-

ment Replacement

4.1. Introduction

Recycling of concrete in producing aggregate is one of the keys to support

environmental conservation. It can reduce the use of natural resources and

waste disposal. The average world production of concrete has reached 20 bil-

lion tons per year, and 40% of all industrial waste is construction and demoli-

tion waste [1,2]. Whereas in Japan, from 2006, 98% of concrete waste has been

CHAPTER 4 Strength and Drying Shrinkage of Concrete Made From Recycled Aggre-

gate by Pulsed Power Technology with Fly Ash as Cement Replacement

47

recycling to be reused as recycled aggregate for road sub-base, underground

stabilization and concrete [1,3].

It is well known that recycled aggregate has lower quality compared to natu-

ral aggregate. Because recycled aggregate contains mortar from the original

concrete, it is more porous and absorptive than many natural aggregates. Recy-

cled coarse aggregate has higher water absorption compare to natural aggregate.

For this reason, drying shrinkage and creep of concrete were significantly in-

creased by the use of recycled aggregate. Therefore, the use of recycled aggre-

gate is mainly confined to low-grade applications [4-6].

The technology to reproduce high quality recycled aggregate from concrete

waste has been developed using pulsed power discharge. It can remove the

mortar from the aggregate thoroughly. It is found that the coarse aggregate re-

produced by electric pulsed discharged energy of 640 kJ has sufficient qualities

of the density in oven dried condition and the water absorption to satisfy the

JIS (Japan Industrial Standard) regulation class H (A5021) [3,7-11]. Therefore,

the application of recycled aggregate concrete by pulsed power technology is

found to be promising.

In addition, it has been reported that the production amount of coal ash in

Japan exceeded over 10 million tons. This amount is expected to increase due

to new construction and expansion of coal-fired power station. However, the

relative amount of fly ash in use for concrete is low [12,13]. Fly ash as cement

replacement positively impacts the durability and workability of concrete [14-



48

17]. Utilization of fly ash as a supplementary cementitious material can pro-

mote sustainable construction by reducing the CO2 emission of cement produc-

tion.

4.2. Objectives

This study has following objectives:

a. Comparing the strength and durability of concrete made from recycled

aggregate by pulsed power technology with natural coarse aggregate

concrete

b. Investigation of the effect of fly ash to the strength and durability of

concrete made from recycled aggregate by pulsed power technology

4.3. Research on Fly Ash Concrete Made From High Quality

Recycled Aggregate

So far, the utilization of recycled aggregate is identical to contribute poor

quality of concrete. As previous research have reported that pulsed power tech-

nology can produce high quality recycled aggregate which satisfied JIS (Japan

Industrial Standard) class H (A 5021) [3,8], therefore, this technique not only

can support the use of recycled aggregate in concrete to effort resource saving,

but also can provide quality which is not inferior to natural aggregate concrete.



49

As the utilization of fly ash generated by coal-fired power plant is still lim-

ited, while the amount of fly ash continue to raise, the attempt to promote the

use of fly ash in concrete is needed to be enhanced.

Positive effect of the utilization of fly ash in concrete has been well known.

Hence, to support the environmental conservation in creating sustainable con-

struction, research on the strength and drying shrinkage of concrete made from

recycled aggregate produced by pulsed power technology due to the use of JIS

type II fly ash as cement replacement were conducted. Compressive strength

test, tensile splitting strength test, modulus of elasticity and drying shrinkage

measurement were carried to evaluate the performance of fly ash concrete

made from recycled aggregate produced by pulsed power technology.

4.4. Experiment


4.4.1.1 Aggregate

To investigate the performance of concrete made of recycled aggregate

concrete, natural coarse aggregate, recycled coarse aggregate, and natural fine

aggregate were used in concrete mix proportion. The natural coarse aggregate

was used in concrete mix proportion as controlled specimen with density of

3.01 gr/cm3 and water absorption of 0.63%. Natural fine aggregate was used in



50

all concrete mixture with density of 2.57 g/cm3.

The recycled coarse aggregate were reclaimed from concrete waste by

pulsed power technology. Previous research has found that the total pulsed

power discharge energy to obtain high quality recycled aggregate was 640 kJ

for 4 kg of concrete waste, or 160 kJ/kg which has similar quality to natural

coarse aggregate [2]. In this study, the discharge energy was set to 6.4 kJ with

180 times of discharge. The total discharge energy was 1152 kJ for 10 kg of

concrete waste, or 115.2 kJ/kg, which is only 72% compared to the reference

having similar quality as natural coarse aggregate. Fig. 4.1 shows the

comparison of recycled aggregate concrete produced by 160 kJ of discharge

energy for every kilogram of concrete waste, and 115.2 kJ of discharge energy

for every kilogram of concrete waste which shows remaining mortar attached

to the aggregate.

(a) (b)

Fig. 4.1 Appearance of recycled aggregate concrete by pulse power

discharge, (a) produced by 160 kJ/kg discharge energy; (b) produced by 115.2

kJ/kg discharge energy.



51

The material properties of recycled coarse aggregate produced by pulsed

power discharge used in the experiment are listed in Table 4.1. It has satisfied

JIS (Japan Industrial Standard) regulation class H (A 5021) for high quality

recycled aggregate [11], even though few mortar still attached to the aggregate.

Furthermore, by washing test, it was found that the amount of powder in

recycled aggregate reached 0.97%.

Table 4.1 Recycled coarse aggregate physical properties

Properties Recycled coarse

aggregate

JIS class H

(A5021)

Oven-dry density (gr/cm3) 2.73 2.5

Water absorption (%) 2.64 3.0

Table 4.2 Sieve analysis of recycled coarse aggregate

Sieve size (mm) Passing (%) 25 mm 100.0 20mm 97.4 15 mm 90.8

10 mm 57.4

5 mm 1.1

The size distribution of the recycled coarse aggregate used in this study is

given in Table 4.2 and illustrated in Fig 4.2. The fineness modulus of the

recycled coarse aggregate reached 6.44. To compare the effect of using

recycled coarse aggregate in concrete, the natural coarse aggregate was set to

have similar size distribution as recycled coarse aggregate which consisted of



52

82% fine gravel and 18% gravel.

Fig. 4.2 Coarse aggregate particle size distribution

4.4.1.2 Cement and Fly Ash

The cement used in the experiment was Portland blast-furnace cement.

Table 4.3 and Table 4.4 show its physical properties and chemical properties,

respectively. Fly ash which satisfied JIS type II was used in this study as partial

cement replacement. The properties of the fly ash are listed in Table 4.5.

Table 4.3 Physical properties of Portland blast-furnace cement

Density (gr/cm3) 3.01

Specific surface area cm2/gr) 3670

Setting time Beginning 2 h 30 min

End 4 h 5 min

Compressive strength (N/mm2)

3 days 20.9

7 days 35.8

28 days 63.2



53

Table 4.4 Chemical properties of Portland blast-furnace cement

Properties Mass (%)

ig.loss 1.74

SiO2 26.34

Al2O3 9.14

Fe2O3 1.59

CaO 54.73

MgO 2.86

TiO2 0.36

MnO 0.08

SO3 1.96

Na2O 0.25

K2O 0.30

P2O5 0.09

Cl 0.007

Total 100.01

Table 4.5 Properties of fly ash

Properties JIS FA type-II standard

SiO2 56.6% A6201 > 45.0

Hygroscopic moisture 0.2% A6201 < 1.0

ig.loss 1.2% A6201 < 5.0

Density 2.36 g/cm3

A6201

R5201 > 1.95

residue on sieve of 45um 3% A6201 < 40

specific surface (Blaine) 4190 cm2/g

A6201

R5201 > 2500

percent flow 106% A6201 > 95

Activity index (28 day) 92% A6201 > 80


methlene blue absorption 0.22 mg/g



54

4.4.2. Experimental Procedure

4.4.2.1 Mix Proportion

The mix proportions in this experiment are described in Table 4.6. Since the

recycled coarse aggregate in this study has satisfied the JIS regulation for high

quality recycled aggregate Class H (A5021), therefore, the recycled coarse

aggregate replaced the use of natural coarse aggregate by 100% with the

maximum aggregate size of 20 mm.

Table 4.6 Concrete mix proportion

Mix ID Water

(kg/m3)

Fly Ash

(%)

Cement

(kg/m3)

Fly Ash

(kg/m3)

Gravel (kg/m3) Sand

(kg/m3) NCA RCA

NCA-0 186 0 338.1 0 1061.8 0 741.7

NCA-10 186 10 304.3 33.8 1061.8 0 741.7

NCA-25 186 25 253.6 84.5 1061.8 0 741.7

NCA-50 186 50 169.0 169.0 1061.8 0 741.7

RCA-0 186 0 338.1 0 0 959.5 741.7

RCA-10 186 10 304.3 33.8 0 959.5 741.7

RCA-25 186 25 253.6 84.5 0 959.5 741.7

RCA-50 186 50 169.0 169.0 0 959.5 741.7

Notes: NCA = Natural Coarse Aggregate

RCA = Recycled Coarse Aggregate

The water-cement ratio used in the experiment was 0.55 in all mixtures. The

percentages of fly ash used in the experiment to replace cement were 0%, 10 %,

25%, and 50% by mass.



55

4.4.2.2 Specimen Casting and Curing

In this experiment, two types of specimens were made for each case.

Cylinder specimens with diameter of 100mm and height of 200 mm were made

to investigate the compressive and tensile splitting strength test according to

ISO 1920-8:2009 (E) [23]. Block specimens having dimensions of 100 mm x

100 mm x 400 mm were prepared for determination of drying shrinkage of

concrete according to ISO 1920-8:2009 (E) [24]. 24 hours after casting, the

specimens were removed from the mold and cured according to ISO 1920-

3:2004 (E) [23]. The cylinder specimens were cured in water at temperature

20C 2

C until their compressive and tensile splitting strength test are

conducted. Block specimens for determination of drying shrinkage were cure at

temperature 20C 2

C with relative humidity of 95% for 7 days.

4.4.3. Test Method

Several test method were conducted to evaluate the performance of concrete

in both fresh concrete and hardened concrete. Determinations of slump and air

content test were conducted for fresh concrete. For hardened concrete, the

cylinder specimens were tested for its compressive strength and tensile splitting

strength test. The block specimens were tested for determination of drying

shrinkage of hardened concrete.



56

4.4.3.1 Fresh Concrete properties

Slump test is the most common method to determine the consistence of

fresh concrete. In this study, determination of slump of fresh concrete for each

case was conducted according to ISO 1920-2:2005 (E) [25].

Air content was performed to measure the total air content in a sample of

fresh concrete. Air content test was conducted for each fresh concrete case.

4.4.3.2 Hardened Concrete properties

For determination of hardened concrete properties, compressive strength

test, tensile splitting strength test, and drying shrinkage test were carried out.

Compressive strength test were performed at age 7, 28, 56 and 112 day. While

tensile splitting strength test was conducted at age 28 day for each case. De-

termination of drying shrinkage of hardened concrete was measured everyday

started at age 7 day to 28 day, and continuously measured twice a week until

age 112 day.


4.5.1. Properties of Fresh Concrete

Concrete fresh properties, such as slump and air content test result are

presented in Fig 4.3. The results show that for the same water-to-binder ratio,

fly ash increases the workability of fresh concrete. Furthermore, fly ash



57

indicates an increase in air content of natural aggregate concrete, but do not

show significant effect to recycled aggregate concrete.

Fig. 4.3 Slump and air content result

4.5.2. Properties of Hardened Concrete

Hardened concrete properties of concrete specimen were tested to evaluate

the effect of fly ash as cement replacement to the performance of concrete

made from recycled coarse aggregate by pulse power technology. The

compressive strength, tensile splitting strength, modulus elasticity, and drying

shrinkage of the specimens were investigated.

4.5.2.1 Compressive Strength

The compressive strength test was performed at age 7, 28, 56 and 112 day.



58

Fig. 4.4, and Fig. 4.5 illustrate the effect of fly ash as cement replacement to

the compressive strength of concrete made from natural coarse aggregate and

recycled coarse aggregate, respectively.

Fig. 4.4 shows that the compressive strength of natural aggregate concrete is

decreased by the use of fly ash as cement replacement in all cases for the same

water-to-binder ratio. In the 28 day strength, 10% fly ash reaches 99% of the

compressive strength of concrete without fly ash. While 25% and 50% fly ash

achieve 83% and 44% of the compressive strength of concrete without fly ash,

respectively.

Fig. 4.4 Compressive strength of specimens made of natural course aggregate

Same trend is also shown by Fig. 4.5 for recycled aggregate concrete with

fly ash as cement replacement. Increased use of fly ash in recycled aggregate

concrete reduces the compressive strength. In the 28 day strength, 10% fly ash

reaches 96% of the compressive strength of concrete without fly ash. Whereas



59

25% and 50% fly ash achieve 87% and 49% of the compressive strength of

concrete without fly ash, respectively.

Fig. 4.5 Compressive strength of specimens made of recycled coarse aggregate

Fig. 4.6 illustrates the effect of natural and recycled aggregate to the

compressive strength of concrete. Fig. 4.6(a) shows that the compressive

strength of concrete made from 100 % recycled aggregate by pulsed power

technology is similar to the concrete made from natural coarse aggregate.

When using fly ash, as shown in Fig. 4.6(b), Fig. 4.6(c) and Fig. 4.6(d),

recycled coarse aggregate concrete performs higher compressive strength

compared to natural aggregate concrete. In 10% fly ash as cement replacement,

the recycled aggregate concrete shows slightly higher compressive strength

compared to natural aggregate concrete. While in higher percentage of fly ash,

recycled aggregate concrete with 25% and 50% fly ash show higher



60

compressive strength which is significant to natural aggregate concrete. These

facts emphasize that pulsed power can produce high quality recycled aggregate.

(a) (b)

(c) (d)

Fig. 4.6 Compressive strength of specimens,

(a) Without fly ash; (b) 10% fly ash; (c) 25% fly ash; (d) 50% fly ash

4.5.2.2 Tensile Splitting Strength

CHAPTER 4 Strength and Drying Shrinkage of Concrete Made From Recycled Aggregate by

Pulsed Power Technology with Fly Ash as Cement Replacement

61

Fig. 4.7 Tensile Splitting Strength

The tensile splitting strength test was performed at the age 28 day for each case. Fig.

4.7 illustrates the tensile splitting test result. This figure shows that concrete from

recycled aggregate by pulsed power technology can achieve higher tensile splitting

strength compared to natural aggregate concrete. This figure also indicates that tensile

strength increase by 10% of fly ash to replace cement, and then gradually reduces by the

increased use of fly ash in concrete.

4.5.2.3 Modulus of Elasticity

Static modulus of elasticity of the concrete specimens are given in Table 4.7, and

drawn in Fig 4.8. It indicates that the modulus of elasticity is decreased by the increased

use of fly ash. However, for the same percentage of fly ash, recycled coarse aggregate

concrete provides higher modulus of elasticity compared to natural aggregate concrete.

Moreover, 10% and 25% fly ash to replace cement perform almost similar modulus

elasticity to 0% fly ash in recycled aggregate concrete.



62

Table 4.7 Modulus of elasticity of concrete specimens

Fly Ash Modulus of elasticity (GPa)

NCA RCA

0% 28.15 27.92

10% 26.64 27.37

25% 25.39 26.78

50% 21.13 22.32

Fig. 4.8 Modulus of elasticity of concrete specimens

4.5.2.4 Drying Shrinkage

Determination of drying shrinkage of hardened concrete was started at age 7 day and

recorded every day until 28 day, and continuously twice a week recorded until age 112

day. Fig. 4.9 and Fig. 4.10 illustrate the effect of fly ash to drying shrinkage of the

concrete made from natural coarse aggregate and recycled coarse aggregate,

respectively.



63

Fig. 4.9 Drying shrinkage of specimens made of natural coarse aggregate

Fig. 4.10 Drying shrinkage of specimens made of recycled coarse aggregate

Drying shrinkage of concrete made of natural coarse aggregate in Fig. 4.9 indicates

that the use of 25% fly ash does not give significant effect, while the 50% fly ash has

decreased the drying shrinkage. In contrast, 10% fly ash as cement replacement increas-

es the drying shrinkage. While in concrete made of recycled aggregate concrete, as

shown in Fig. 4.10, drying shrinkage is reduced as fly ash percentage increases.



64

Fig. 4.11, Fig. 4.12, Fig. 4.13 and Fig 4.14 illustrate the effect of recycled

aggregate to the drying shrinkage of concrete with 0%, 10%, 25%, and 50% fly

ash, respectively. Fig. 4.11 shows similar drying shrinkage of concrete made

from natural aggregate and recycled aggregate by the pulsed power technology

in concrete without fly ash. It clarifies that recycled coarse aggregate produced

by the pulsed power technology can reach same performance as natural coarse

aggregate.

Fig. 4.11 Drying shrinkage of specimens without fly ash

Fig. 4.12 Drying shrinkage of specimens with 10% of fly ash as cement

replacement



65


replacement


replacement

In concrete with 10% and 20% fly ash as cement replacement, recycled

aggregate concrete shows significant reduction in drying shrinkage compared

to natural aggregate concrete as shown in Fig. 4.12 and Fig. 4.12, respectively.

In contrast, when using recycled aggregate in concrete with 50% fly ash, it

shows an increase in drying shrinkage compared to natural aggregate concrete.

Furthermore, using the same scale of drying shrinkage, from Fig. 4.12 to Fig.



66

4.14, the trend of drying shrinkage of recycled aggregate concrete is increased

by the increased use of fly ash compared to natural aggregate concrete.

4.6. Conclusion

The compressive strength, tensile splitting strength and drying shrinkage of

recycled aggregate concrete produced by the pulsed power technology were

investigated to characterize the effect of JIS type II fly ash as cement

replacement to the performance of concrete. The following conclusions are

drawn from the test result:

1. Pulsed power technology has been proven to reproduce high quality

recycled aggregate. By 72% of the reference discharge energy for

reproducing recycled coarse aggregate having similar quality to natural

coarse aggregate using the pulsed power technology, its compressive

strength, modulus of elasticity and drying shrinkage does not show

significant difference to the concrete made from natural coarse

aggregate.

2. The use of fly ash as cement replacement can reduce the compressive

and tensile splitting strength, and modulus of elasticity both in natural

aggregate concrete and recycled aggregate concrete. However, it can

minimize the drying shrinkage.

3. In concrete made from recycled aggregate produced by the pulsed

power technology, the utilization of fly ash has shown improvement in

strength and reduce drying shrinkage

4. To maximize the utilization of fly ash and recycled aggregate concrete,

replacing 25% of cement weight with fly ash in concrete made from

recycled aggregate by pulsed power technology has shown reduction in

drying shrinkage without substantial reduction in strength.



67

Bibliography

1. Sakai K, “Recycling concrete, the present state and future perspective”,

TCG-JSCE JOINT SEMINAR. Nov. 20, 2009, Athens

2. Marinkovic S, Ignjatovic I, “Recycled aggregate concrete for structural use

- an overview of technologies, properties, and applications”, ACES Work-

shop, Innovative Materials and Techniques in Concrete Construction, Cor-

fu, October 10-12, 2010


from concrete waste using pulsed power technology”, S. Clean Technolo-

gy, www.ct-si.org, 2010,ISBN 978-1-4398-3419-0

4. McGovern M, “Recycled aggregate for reinforced concrete”, CT022 —

July 2002 Vol. 23, No. 2 Concrete Technology today, PCA (Portland Ce-

ment association)

5. Tam WYV, Tam CM, Wang Y, “ Optimization on Proportion for rcycled

aggregate in concrete using two-stage mixing approach”, Construction and

Building Materials Journal, Vol. 21, 2007, pp. 1928-1939

6. Kou S., “Reusing recycled aggregate in structural concrete”, PhD thesis,


7. Maeda S, Shigeishi M, Namihira T, Iizasa S, “Research on concrete ag-

gregate collection technology by pulsed power discharge”, 34th

Conference

on Our World in Concrete & Structures, 16-18 August 2009



68



cled coarse aggregates by pulsed power discharged”, 1-4244-0914-4/07

©2007 IEEE., Kumamoto University, 2007

9. Inoue S, et al., “Coarse aggregate recycling by pulsed discharge inside of

concrete”, Acta Physica Polonica A, Vol. 115 No. 6, 2009, pp. 1107-1109

10. Namihira T, Wang D, Akiyama H, “Pulsed power technology for pollution

control”, Acta Physica Polonica A, Vol. 115 No. 6, 2009, pp. 953-955

11. Japanese Standard Association, JIS A 5021”Recycled aggregate for con-

crete – class H”, 2005


Third International Conference on Sustainable Concstruction Materials

and Technology Proceeding, August 18-21, 2013



ronment”, 2007 World of Coal Ash (WOCA), May 7-10, 2007, Nothern

Kentucky, USA

14. Nath P, Sarker P, “ Effect of fly ash on the durability properties of high

strength concrete”, Procedia Engineering, Vol. 14, 2011, pp. 1149-1156

15. Nath P, Sarker P, “Effect of mixture proportion on the drying shrinkage

and permeation properties of high strength concrete containing class F fly

ash”, KSCE Journal of Civil Engineering, Vol. Issue 6, 2013, pp 1437-

1445

16. Naik TR, Sivasundaram V, Singh SS, “Use of high-volume class F fly ash

for structural grade concrete”, Transportation Record No. 1301, TRB, Na-

tional Research Council, Washington, D.C., January (1991), pp. 40-47

17. Mokarem DW, “ Development of concrete shrinkage performance specifi-

cations”, Disertation, Faculty of theVirginia Polytechnic Institute and State



69

University, 2002

18. Tam WYV, Gao XF, Tam CM, “Microstructural analysis of recycled ag-

gregate concrete produced from two-stage mixing approach, Cement and

Concrete Research Journal, Vol. 35, Issue 6, June 2005, pp. 1195-1203

19. Tam WYV, Tam CM, “Assessment of durability of recycled aggregate

concrete produced by two-stage mixing approach”, Journal Materials Sci-

ence, Vol. 42, 2007, pp. 3592–3602.

20. Tam WYV, Tam CM, “Diversifying two-stage mixing approach (TSMA)

for recycled aggregate concrete: TSMAs and TSMAsc”, Construction and

Building Materials Journal, Vol. 22, 2008, pp. 2068–2077

21. Salas A, Roesler JR, Lange D, “Batching effects on properties of recycled

concrete aggregates for airfield rigid pavement”, 2010 FAA Worldwide

Airport Technology Transfer Conference, April 20-22, 2010

22. Jeong H, “Processing and properties of recycled aggregate concrete”, The-

sis, Graduate College of University of Illinois at Urbana-Champaign, 2011

23. ISO 1920-3:2004(E), Testing of concrete – Part 3: Making and curing test

specimens.

24. ISO 1920-8:200(E), Testing of concrete – Part 8: Determination of drying

shrinkage of concrete for samples prepared in the field or in the laboratory.

25. ISO 1920-2:2005(E), Testing of concrete – Part2: Properties of fresh con-

crete.

70

CHAPTER 5

Application 3 : Performance of Fly Ash Concrete

Made from Recycled Aggregate by Pulsed Power

Technology With Two-Stage Mixing Approach

5.1. Introduction

The utilization of recycled aggregate from construction and demolition

waste recently has been well developed due to the awareness of natural re-

source depletion and limited landfill disposal. However, the characteristic of

recycled aggregate could be different by its parent concrete since it was de-

signed for different purpose, strength, and durability [1]. Since recycled aggre-

gate is reproduced from concrete waste which has undergone years of services,

it is well known that recycled aggregate concrete indicates several weakness

such as low density, higher water absorption, and higher porosity that limit the

utilization of recycled aggregate concrete to lower grade application [2,3].

CHAPTER 5 Performance of Fly Ash Concrete Made from Recycled Aggregate by

Pulsed Power Technology with Two-Stage Mixing Approach

71

To encourage the utilization of recycled aggregate in producing concrete,

Tam et al. introduced Two-Stage Mixing Approach (TSMA) to upgrade the

performance of recycled aggregate concrete [2,4-6]. Their research show that

TSMA can improve the properties of recycled aggregate concrete.

On the other hand, the use of fly ash in the manufacture of concrete has

been widely reported. In addition to supporting sustainable construction by re-

duce CO2 emission of cement production, fly ash as a supplementary ce-

mentitious material can also improve the performance of concrete both worka-

bility and durability [7-12]. Therefore, the performance of fly ash concrete

made from recycled aggregate concrete using TSMA in the mixing process is

studied.

5.2. Objectives

This study has following objectives :

a. To investigate the effect of Two-Stage Mixing Approach (TSMA) to the

performance of concrete made from recycled aggregate produced by

pulsed power technology.

b. To investigate the effect of fly ash to strength and durability of concrete

made from recycled aggregate by pulsed power technology with TSMA

5.3. Two-Stage Mixing Approach (TSMA)

Due to low quality of recycled aggregate, a two-stage mixing approach was

proposed to improve the strength and rigidity of recycled aggregate concrete

[5]. The recycled aggregate is initially coated with cementitious paste to im-

prove the uniformity and strength of recycled aggregate. In this method, mix-

ing process is divided into two parts with required water proportionally split



72

and added at different mixing time. Initial water is used for formation of thin

layer of cement slurry on the surface of recycled aggregate and fills up old

cracks and voids [5].

It is reported that around 25-40% of recycled aggregate substitution pro-

vides optimum strength using TSMA [4]. Furthermore, deformation and per-

meability of recycled aggregate concrete can be enhanced by adopting TSMA

and proved to be an effective method for increasing durability of recycled ag-

gregate concrete [2]. Following up the study on TSMA, several researchers

have reported that the workability of recycled coarse aggregate concrete is sim-

ilar to the natural aggregate concrete and compressive and splitting tensile

strength of the recycled aggregate concrete which are specifically required in

the construction of airfield concrete pavements [13]. Moreover, initial moisture

states of recycled aggregate strongly give influence to the strength and shrink-

age of recycled aggregate concrete with two-stage mixing method [1].

5.4. Research on Fly Ash Concrete Made From Recycled Ag-

gregate with TSMA

The experiment on the use of fly ash in concrete made from high quality

recycled aggregates produce by the pulsed power technology has been de-

scribed in chapter 4. It is clear that the strength of concrete is reduced by the

increased use of fly ash. However, the utilization of fly ash in recycled aggre-

gate concrete gives positive impact in reducing drying shrinkage.

Previous research has found that two-stage mixing approach (TSMA) in

producing recycled aggregate shows improvement in strength. Therefore, the

effect of TSMA to the performance of concrete made from high quality recy-

cled aggregate is needed. Further, the performance of fly ash concrete made

from recycled aggregate concrete produce by pulsed power using TSMA in the



73

mixing process is needed to be examined. It is because fly ash can reduce dry-

ing shrinkage, yet it can reduce the strength of concrete in same water-to-

binder ratio. Accordingly, the TSMA is expected to overcome this weakness.

5.5. Experiment


5.5.1.1 Aggregate

The recycled aggregate is used in the experiment was reclaimed by the

pulsed power technology. In this study, the discharge energy was set to 6.4 kJ

with 180 times of discharge. The total discharge energy was 1152 kJ for 10 kg

of concrete waste, or 115.2 kJ/kg. Natural fine aggregate was used in all

concrete mixture with density of 2.57 g/cm3. The size distribution of the

recycled coarse aggregate used in this study is given in Fig 5.1.

Fig. 5.1 Coarse aggregate particle size distribution

The material properties of recycled coarse aggregate are listed in Table 5.1



74

which has satisfied JIS (Japan Industrial Standard) regulation class H (A 5021)

for high quality recycled aggregate [14].

Table 5.1 Recycled coarse aggregate physical properties

Properties Recycled coarse aggregate

JIS class H (A5021)







Setting time Beginning 2 h 30 min

End 4 h 5 min


3 days 20.9

7 days 35.8

28 days 63.2


Properties Mass (%)

ig.loss 1.74

SiO2 26.34

Al2O3 9.14

Fe2O3 1.59

CaO 54.73

MgO 2.86

TiO2 0.36

MnO 0.08

SO3 1.96

Na2O 0.25

K2O 0.30

P2O5 0.09

Cl 0.007

Total 100.01



75


Table 5.2 and Table 5.3 show the physical properties and chemical properties

of Portland blast-furnace, respectively. Fly ash which satisfied JIS type II was

used in this study as partial cement replacement. The properties of the fly ash

are listed in Table 5.4.


Properties

JIS FA type-II

standard

SiO2 56.6% A6201 > 45.0


ig.loss 1.2% A6201 < 5.0

Density 2.36 g/cm3

A6201

R5201 > 1.95



A6201

R5201 > 2500






5.5.2.1 Mix Proportion and Mixing Approach

The mix proportion and mixing approach in this experiment are described in

Table 5.5. The percentages of fly ash used in the experiment to replace cement

were 0%, 25%, and 50% by mas.

To compare the effect of different mixing approach to the performance of

concrete, two types of mixing approach were used. Normal Mixing Approach

(NMA) is the common mixing approach used to make concrete, where cement,

sand, water and gravel are mixed in one stage. While in Two-Stage Mixing



76

Approach (TSMA), required water was proportionally split and added at

different mixing time. The first 50% of water was mixed with sand and

recycled coarse aggregate, and then the remaining water and cement were

added in the last mixing process.

Table 5.5 Concrete mix proportion and mixing approach

Mix ID Water

(kg/m3)

Fly

Ash

(%)

Cement

(kg/m3)

Fly Ash

(kg/m3)

Gravel

(kg/m3)

Sand

(kg/m3)

Mixing

approach

RCA

NMA-0 186 0 338.1 0 959.5 741.7 NMA

NMA-25 186 25 253.6 84.5 959.5 741.7 NMA

NMA-50 186 50 169.0 169.0 959.5 741.7 NMA

TSMA-0 186 0 338.1 0 959.5 741.7 TSMA

TSMA-25 186 25 253.6 84.5 959.5 741.7 TSMA

TSMA-50 186 50 169.0 169.0 959.5 741.7 TSMA

Notes: NMA = Normal Mixing Approach

TSMA = Two-Stage Mixing Approach


Two types of specimen were made for each case in this study. Cylinder

specimens with diameter of 100mm and height of 200 mm were made to

investigate the compressive and tensile splitting strength test according to ISO

1920-8:2009 (E) [23]. Block specimens having dimensions of 100 mm x 100

mm x 400 mm were prepared for determination of drying shrinkage of concrete

according to ISO 1920-8:2009 (E) [24].

The specimens were removed from the mold and cured according to ISO

1920-3:2004 (E) [23] in 24 hours after casting. The cylinder specimens were

cured in water at temperature 20C 2

C until their compressive and tensile

splitting strength test are conducted. Block specimens for determination of

drying shrinkage were cure at temperature 20C 2

C with relative humidity



77

of 95% for 7 days.

5.5.3. Test Method

Several test method were conducted to evaluate the performance of concrete

in both fresh concrete and hardened concrete. Determinations of slump and air

content test were conducted for fresh concrete. For hardened concrete, the

cylinder specimens were tested for its compressive strength and tensile splitting

strength test. The block specimens were tested for determination of drying

shrinkage of hardened concrete.

5.5.3.1 Fresh Concrete properties

To determine the consistence of fresh concrete, slump test was conducted

according to ISO 1920-2:2005 (E) [25]. Air content was also performed to

measure the total air content in a sample of fresh concrete for all specimens.

5.5.3.2 Hardened Concrete properties

Compressive strength test, tensile splitting strength test, and drying

shrinkage test were conducted to evaluate the hardened concrete properties.

Compressive strength test were performed at age 7, 28, 56 and 112 day, and

tensile splitting strength test was conducted at age 28 day. Drying shrinkage

measurement was carried everyday started at age 7 day to 28 day, and

continuously measured twice a week until age 112 day.



78


5.6.1. Properties of Fresh Concrete

Table 5.6 Concrete fresh properties

Mix ID Slump

(cm)

Air content

(%)

NMA-0 10.3 0.9

NMA- 25 17.4 0.8

NMA- 50 18.7 0.8

TSMA- 0 13.7 0.9

TSMA-25 10.1 1.2

TSMA -50 13.5 1.2

Fig. 5.2 Slump and air content result

Concrete fresh properties, such as slump and air content test result are

presented in Table 5.6 and illustrates in Fig 5.2. The results show that fly ash

increases the workability of fresh recycled aggregate concrete using normal



79

mixing approach (NMA). However, it does not show significant effect in

recycled aggregate concrete with two-stage mixing approach (TSMA).

Furthermore, TSMA showed higher air content in producing recycled

aggregate concrete compared to NMA.

5.6.2. Properties of Hardened Concrete

5.6.2.1 Compressive Strength

The compressive strength test of recycled aggregate concrete was performed

at age 7, 28, 56 and 112 day. Fig. 5.3 and Fig. 5.4 illustrate the effect of fly ash

as cement replacement to the compressive strength of concrete made from

recycled coarse aggregate using normal mixing approach and two-stage mixing

approach, respectively.

Fig. 5.3 Compressive strength of specimens made of NMA

Fig. 5.3 shows that the compressive strength of recycled aggregate concrete

using NMA is decreased by the use of fly ash as cement replacement in all



80

cases for the same water-to-binder ratio. In the 28 day strength, 25% fly ash

reaches 87.28% of the compressive strength of concrete without fly ash. While

50% fly ash achieves 48.67% of compressive strength of concrete without fly

ash.

When using TSMA to produce recycled aggregate concrete, Fig. 4.5 shows

that the compressive strength is reduced by the increased use of fly ash without

adjustment in water-to-binder ratio. In the 28 day strength, 25% fly ash reaches

91.86% of compressive strength of concrete without fly ash. Whereas 50% fly

ash achieves 48.96% of the compressive strength of concrete without fly ash.

Fig. 5.4 Compressive strength of specimens made of TSMA

Fig. 5.5 illustrates the effect of different mixing approach to the

compressive strength of concrete. Fig. 5.5(a) shows that without fly ash, the

compressive strength of concrete made from recycled aggregate by pulsed

power technology using NMA is similar to the recycled aggregate concrete

using TSMA. However, when 25% fly ash replaced cement mass, as shown in

Fig. 5.5(b), TSMA shows improvement in the compressive strength of recycled



81

aggregate concrete compared to NMA. Furthermore, with 50% fly ash as

cement replacement, TSMA shows the higher compressive strength in the age

over 56 day compared to NMA in producing recycled aggregate concrete.

(a) (b)

(c)

Fig. 5.5 Compressive strength of specimens,

(a) without fly ash; (b) 25% fly ash; (c) 50% fly ash

5.6.2.2 Tensile Splitting Strength

Tensile splitting strength test was performed at age 28 day for each case and

the results are illustrated in Fig. 5.6. It shows that the tensile strength is re-

duced by the increased use of fly ash in recycled aggregate concrete using both

NMA and TSMA. Further, without fly ash, recycled aggregate concrete using



82

TSMA does not show improvement. The tensile splitting strength of recycled

aggregate concrete using TSMA is 2.96 MPa, which is slightly lower from the

recycled aggregate concrete using NMA that reaches 2.99 MPa in the 28-day

strength. However, in fly ash concrete, TSMA indicates improvement in the

tensile splitting strength, which increases its strength up to 13.8% with 25% fly

ash, and 5.7% with 50% fly ash compared to NMA.

Fig. 5.6 Tensile Splitting Strength

5.6.2.3 Modulus of Elasticity

Table 5.7 Modulus elasticity of concrete specimens

Fly Ash Modulus of elasticity (GPa)

NMA TSMA

0% 27.92 27.61

25% 26.78 26.73

50% 22.32 20.3

Static modulus of elasticity of the concrete specimens are given in Table

5.7, and drawn in Fig 5.7. It indicates that the modulus of elasticity is de-

creased by the increased use of fly ash. Further, in recycled aggregate concrete,

TSMA has lower modulus elasticity compared to NMA in all percentage of fly



83

ash. TSMA decreases the modulus of elasticity by 1.1%, 0.2% and 9.0% for

0%, 25% and 50% fly ash as cement replacement, respectively, compared to

NMA in producing recycled aggregate concrete.

Fig. 5.7 Modulus of elasticity of concrete specimens

5.6.2.4 Drying Shrinkage

Determination of drying shrinkage of hardened concrete was started at age

7 day and recorded every day until 28 day, and continuously twice a week rec-

orded until age 112 day. Fig. 5.8 and Fig. 5.9 illustrate the effect of fly ash to

drying shrinkage of the recycled aggregate concrete with normal mixing ap-

proach and two-stage mixing approach, respectively.

Fig. 5.8 indicates that the use of fly ash reduces drying shrinkage of recy-

cled aggregate concrete using NMA. Nevertheless, 25% fly ash does not show

significant different to 50% fly ash as cement replacement in reducing drying

shrinkage. While in Fig. 5.9, the reduction of drying shrinkage of recycled ag-

gregate concrete using TSMA is shown in the age older than 56 day. Before 56

day, the use of fly ash does not indicate the reduction on drying shrinkage.

Even though in the age older than 56 day the utilization of fly ash in recycled



84

aggregate concrete using TSMA shows the reduction in drying shrinkage,

however, the reduction of 50% fly ash is not significant to 25% fly ash in re-

placing cement.

Fig. 5.8 Drying shrinkage of specimens made of NMA

Fig. 5.9 Drying shrinkage of specimens made of TSMA

Fig. 5.10, Fig. 5.11, and Fig 5.12 illustrate the effect of different mixing

approach to the drying shrinkage of recycled aggregate concrete with 0%, 25%



85

and 50% fly ash as cement replacement, respectively. Fig. 5.10 shows similar

drying shrinkage of recycled aggregate concrete without fly ash using NMA

and TSMA. It indicates similar drying shrinkage pattern between NMA and

TSMA in producing recycled aggregate concrete.

Fig. 5.10 Drying shrinkage of specimens without fly ash

As shown in Fig. 5.11, by replacing 25% cement partially with fly ash, re-

cycled aggregate concrete using TSMA indicates to increase drying shrinkage

of recycled aggregate concrete compared to NMA, especially after age 28 day.

While in 50% fly ash, TSMA shows to increase shrinkage significantly com-

pares to NMA from the early age of recycled aggregate concrete. It clarifies

that in producing fly ash concrete made from recycled aggregate, TSMA does

not show reduction to drying shrinkage.



86


replacement


replacement

5.7. Conclusion

Compressive strength, tensile splitting strength and drying shrinkage of

recycled aggregate concrete produced by the pulsed power technology were

investigated to characterize the effect of JIS type II fly ash as cement

replacement and different mixing approach to the performance of concrete. The



87

following conclusions are drawn from the test result:

1. In fresh recycled aggregate concrete with normal mixing approach, fly ash

can increase the workability, but does not show significant effect to air

content.

2. By applying TSMA to produced recycled aggregate concrete, it shows

higher air content compared to NMA.

3. The use of fly ash as cement replacement can reduce the compressive and

tensile splitting strength and modulus of elasticity of recycled aggregate

concrete when using both NMA and TSMA.

4. In recycled aggregate concrete without fly ash, TSMA does not show im-

provement in the compressive strength and tensile splitting strength with

same water-to-binder ratio.

5. In fly ash concrete made from recycled aggregate, TSMA improves the

compressive strength and tensile splitting strength compared to NMA. In

the same percentage of fly ash, TSMA shows higher strength compared to

NMA. In the 28 day strength, 25% fly ash reaches 87.28% and 91.86% of

compressive strength of concrete without fly ash when using NMA and

TSMA, respectively. While 50% fly ash achieves 48.67% and 48.96% of

compressive strength of concrete without fly ash when using NMA and

TSMA, respectively.

6. By replacing 25% of cement weight with fly ash, concrete made from

recycled aggregate by the pulsed power technology using TSMA has

shown to improve strength without major increased in drying shrinkage



88

Bibliography

1. Jeong H, “Processing and properties of recycled aggregate concrete”, The-

sis, Graduate College of University of Illinois at Urbana-Champaign, 2011,

Urbana, Illinois

2. Tam WYV, Tam CM, “Assessment of durability of recycled aggregate

concrete produced by two-stage mixing approach”, Journal Materials Sci-

ence, Vol. 42, 2007, pp. 3592–3602.

3. McGovern M, “Recycled aggregate for reinforced concrete”, CT022 —

July 2002 Vol. 23, No. 2 Concrete Technology today, PCA (Portland Ce-

ment association)

4. Tam WYV, Tam CM, Wang Y, “Optimization on Proportion for Recycled

Aggregate in Concrete Using Two-Stage Mixing Approach”, Construction

and Building Materials Journal, Vol. 21, 2007, pp. 1928-1939

5. Tam WYV, Gao XF, Tam CM, “Microstructural analysis of recycled ag-

gregate concrete produced from two-stage mixing approach, Cement and

Concrete Research Journal, Vol. 35, Issue 6, June 2005, pp. 1195-1203

6. Tam WYV, Tam CM, “Diversifying two-stage mixing approach (TSMA)

for recycled aggregate concrete: TSMAs and TSMAsc”, Construction and

Building Materials Journal, Vol. 22, 2008, pp. 2068–2077



8. Nath P, Sarker P, “Effect of mixture proportion on the drying shrinkage and



89

permeation properties of high strength concrete containing class F fly ash”,

KSCE Journal of Civil Engineering, Vol. Issue 6, 2013, pp 1437-1445





cations”, Disertation, Faculty of theVirginia Polytechnic Institute and State

University, 2002

11. Limbachiya M, Meddah MS, Ouchagour Y, “Use of recycled aggregate in

fly ash concrete”, Construction and Building Materials Journal, Vol. 27,

2012, pp. 439-449


Third International Conference on Sustainable Concstruction Materials and


13. Salas A, Roesler JR, Lange D, “Batching effects on properties of recycled

concrete aggregates for airfield rigid pavement”, 2010 FAA Worldwide

Airport Technology Transfer Conference, April 20-22, 2010, Atlantic City,

New Jersey, USA

14. Japanese Standard Association, JIS A 5021”Recycled aggregate for con-

crete – class H”, 2005


from concrete waste using pulsed power technology”, S. Clean Technology,

www.ct-si.org, 2010,ISBN 978-1-4398-3419-0

16. Sakai K, “Recycling concrete, the present state and future perspective”,

TCG-JSCE Joint Seminar. Nov. 20, 2009

17. Kou S., “Reusing recycled aggregate in structural concrete”, PhD thesis,


18. Maeda S, Shigeishi M, Namihira T, Iizasa S, “Research on concrete aggre-



90

gate collection technology by pulsed power discharge”, 34th

Conference on

Our World in Concrete & Structures, 16-18 August 2009



cled coarse aggregates by pulsed power discharged”, 1-4244-0914-4/07

©2007 IEEE., Kumamoto University, 2007

20. Inoue S, et al., “Coarse aggregate recycling by pulsed discharge inside of

concrete”, Acta Physica Polonica A, Vol. 115 No. 6, 2009, pp. 1107-1109

21. Namihira T, Wang D, Akiyama H, “Pulsed power technology for pollution

control”, Acta Physica Polonica A, Vol. 115 No. 6, 2009, pp. 953-955



ronment”, 2007 World of Coal Ash (WOCA), May 7-10, 2007, Nothern

Kentucky, USA

23. ISO 1920-3:2004(E), Testing of concrete – Part 3: Making and curing test

specimens.

24. ISO 1920-8:200(E), Testing of concrete – Part 8: Determination of drying

shrinkage of concrete for samples prepared in the field or in the laboratory.

25. ISO 1920-2:2005(E), Testing of concrete – Part2: Properties of fresh con-

crete.

91

CHAPTER 6

Application 4 : Effect of Fly Ash as Partial Re-

placement of Low Quality Fine Aggregate on

The Performance of Mortar

6.1. Introduction

Fly ash, generated during the combustion of coal for energy production, is

an industrial by-product which is recognized as an environmental pollutant [1].

Due to its negative impact, the utilization of fly ash has drawn attention from

researchers. Even though many attempts have been made to find new applica-

tion fields for fly ash, the utilization in concrete and cement is still the most

effective one, both from economic and ecologic point of view [2].

Fly ash has been used in concrete as a raw material for cement production,

as an ingredient in blended cement, and as partial replacement for cement in

concrete. Fly ash is also used as a partial replacement of fine aggregate as well

as in the production of light weight aggregate for concrete [3].

CHAPTER 6 Effect of Fly Ash as Partial Replacement of Low Quality Fine Aggregate

on the Performance of Mortar

92

The utilization of fly ash as cement replacement has been well documented.

Fly ash can increase the workability and durability [4-7], improve strength in

age over 90 days [8], and improve resistance to chloride ingress [9]. However,

the use of fly ash as a fine aggregate replacement rarely reported, especially on

the low quality of fine aggregate.

6.2. Objectives

This study has following objectives:

a. Investigate the performance of mortar made from low quality fine aggregate.

b. Investigate the effect of fly ash as a partial replacement of low quality fine

aggregate on the performance of mortar

6.3. Research on Fly Ash as Partial Replacement of Fine Ag-

gregate

With the increased amount of fly ash generated each year, the utilization of

fly ash needs to be improved in order to reduce environmental load. Although

research on the use of fly ash in concrete as a supplementary cementitious ma-

terial has long been developed, nevertheless the research on the utilization of

fly ash as a fine aggregate replacement is still limited.

Previous research on fly ash as fine aggregate replacement has shown that

fly ash can improve the compressive strength, tensile splitting strength, flexural

strength and modulus of elasticity of concrete [10-13]. However, the utilization

of fly ash as low quality fine aggregate has not been reported.

In terms of volume, the use of fly ash as replacement for fine aggregate

provides a more significant reduction in the volume of environmental load re-



93

sulted by fly ash compare to its utilization as a supplementary cementitious ma-

terial.

6.4. Experiment


6.4.1.1 Fine Aggregate

Hyoujun-sa, a standardized sand in accordance with JIS R 5201 was used in

mortar as controlled specimen. To investigate the effect of fly as partial

replacement of low quality fine aggregate on the performance of mortar,

crushed stone sand was used as low quality fine aggregate. Table 6.1 describes

the physical properties of standardized sand (JIS R 5201) and crushed stone

sand. It is clear that compared to standardized sand, crushed stone sand has a

much higher water absorption rate.

Table 6.1 Fine Aggregate Physical Properties

Crushed stone sand Standardized Sand

(JIS R 5021)



Table 6.2 Sieve analysis of Crushed stone sand

Sieve size (mm) Passing Weight (%)

5 mm 99.94

2.5 mm 78.33

1.2 mm 49.87

0.6 mm 32.81

0.3 mm 19.97

0.15 mm 10.59



94

Table 6.3 Granularity of Standardized Sand

Sieve size (mm) Remaining Weight (%)

2 mm 0

1.6 mm 75

1 mm 335

0.5 mm 675

0.16 mm 875

0.08 mm 991

Table 6.2 and Table 6.3 list the size distribution of crushed stone sand and

standardized sand, respectively. The size distribution curves of crushed stone

sand and standardized sand are described in Fig 6.1.

Fig 6.1 Size Distribution of Crushed Stone Sand and Standardized Sand



95



Table 6.4 and Table 6.5 show its physical properties and chemical properties,

respectively. Fly ash which satisfied JIS type II was used in this study as partial

fine aggregate replacement. The properties of the fly ash are listed in Table 6.6.




Setting time

Beginning 2 h 30 min

End 4 h 5 min


3 days 20.9

7 days 35.8

28 days 63.2


Properties Mass (%)

ig.loss 1.74

SiO2 26.34

Al2O3 9.14

Fe2O3 1.59

CaO 54.73

MgO 2.86

TiO2 0.36

MnO 0.08

SO3 1.96

Na2O 0.25

K2O 0.30

P2O5 0.09

Cl 0.007

Total 100.01



96


Properties

JIS FA type-II

standard

SiO2 56.6% A6201 > 45.0


ig.loss 1.2% A6201 < 5.0

Density 2.36 g/cm3

A6201

R5201 > 1.95



A6201

R5201 > 2500






6.4.2.1 Mix Proportion

Standardized sand of JIS R 5201 was used as controlled specimen. The

crushed sand was partially replaced by 10%, 20%, and 30% of fly ash by

volume in the mortar mix proportion. Water-to-cement ratio was set to 55%.

The mix proportions were managed to have same consistence as flow of

standardized sand with tolerance of 4mm. The mix proportions in this

experiment are described in Table 6.7.

Table 6.7 Mortar Mix Proportions

Sample W/C

(%)

Water

(g)

Cement

(g)

Sand (g) Fly Ash

(g)

Flow

(mm)

Ss 55 286 520 1350 0 241

Cs 55 350 636.4 1163 0 241

Cs+10%FA 55 360 654.5 1006 92 238

Cs+20%FA 55 375 681.8 839 173 240

Cs+30%FA 55 395 718.2 670 237 237

Note: Ss = Standardized sand; Cs = Crushed stone sand; FA = Fly ash



97


In this experiment, mortar block specimens having dimensions of 40mm x

40mmx 160mm were prepare for the flexural strength test, compressive

strength test and determination of drying shrinkage.

24 hours after casting, the specimens were removed from the mold and

cured according to ISO 1920-3:2004(E). The specimen was cured in water at

temperature 20C 2C for certain days before compressive and flexural

strength test, while the for determination of drying shrinkage, the specimens

were cured for 7 days.

6.4.3. Test Method

Several test method were conducted to evaluate the performance of mortar

in hardened mortar. For determination of hardened mortar properties,

compressive strength test, flexural strength test, and drying shrinkage test were

conducted. Compressive strength test and flexural strength test were performed

at age 7, 28, 56 and 112 day. Determination of drying shrinkage of hardened

concrete were started at age 7 day and continued until age 112 day.


6.5.1. Compressive Strength

The result of the compressive strength of mortar is listed in Table 6.8 and

illustrated in Fig. 6.8. The results show that the quality of crushed stone sand

mortar without fly ash as fine aggregate replacement is significantly lower than

standardized sand (JIS R 5201). The compressive strength of crushed stone

sand mortar without fly ash achieves 72.86%, 75.80%, 80.89% and 91.42% of



98

the compressive strength of standardized mortar and for 7 day, 28 day, 56 day

and 112 day, respectively. While in crushed stone sand mortar with fly ash as

fine aggregate replacement, 10% fly ash shows a slightly higher compressive

strength compared to crushed stone sand mortar without fly ash in early age up

to 56 day and gradually increases and approaching the compressive strength of

standardized sand mortar in 112 day. The compressive strength of crushed

stone sand mortar with 10% fly ash to replace fine aggregate achieves 74.15%,

78.15%, 81.31% and 99.14 % of the compressive strength of standardized sand

mortar for 7 day, 28 day, 56 day and 112 day, respectively. Crushed stone sand

mortar with 20% fly ash as fine aggregate replacement shows a higher

compressive strength compared to crushed stone sand mortar without fly ash in

7 day-strength. In 28 day and 56 day, its compressive strength is lower than

crushed stone sand mortar without fly ash. However, it gradually increases and

approaching the compressive strength of standardized sand mortar in 112 day

which is higher than the compressive strength of crushed stone sand mortar

with 10% fly ash as fine aggregate replacement. The compressive strength of

crushed stone sand mortar with 20% fly ash to replace fine aggregate achieves

76.66%, 75.09%, 78.20% and 99.26 % of the compressive strength of

standardized sand mortar for 7 day, 28 day, 56 day and 112 day, respectively.

Furthermore, the compressive strength of crushed stone sand mortar with 30%

fly ash to replace fine aggregate shows reduction compared to crushed stone

mortar without fly ash in 7 day, 28 day and 56 day. However, it exceeds the

compressive strength of crushed stone sand mortar without fly ash in 112 day

strength. The compressive strength of crushed stone sand mortar with 30% fly

ash to replace fine aggregate achieves 71.99%, 72.92%, 76.12% and 92.08% of

the compressive strength of standardized sand mortar for 7 day, 28 day, 56 day

and 112 day, respectively.



99

Table 6.8 Compressive strength test of mortar specimens

Mix ID Compressive strength (MPa)

7 day 28 day 56 day 112 day

Ss 29.64 56.26 68.61 71.38

Cs 21.59 42.64 55.50 65.25

Cs+10%FA 21.97 43.96 55.79 70.76

Cs+20%FA 22.71 42.24 53.66 70.84

Cs+30%FA 21.33 41.02 52.23 65.72

Fig. 6.2 Compressive strength of mortar specimens

6.5.2. Flexural Strength

Table 6.9 is given for flexural strength test results. The results are also

illustrated in Fig. 6.3. It shows that the use of crushed stone stand mortar

without fly ash reached 80.11%, 88.91%, 90.56% and 89.91 of the flexural

strength of standardized sand mortar in 7-day, 28-day, 56-day and 112-day

strength, respectively. Moreover, with 10% fly ash to replace fine aggregate in



100

crushed stone sand mortar, it performed a small increase of flexural strength in

early age day, but reduced up to 10.45% in 28-day strength. When the amount

of fly ash increases, the flexural strength of crushed stone sand mortar indicates

reduction. 20% and 30% fly ash reduces 16.97% and 32.49% of flexural

strength in 28-day strength, respectively. This reduction continues to increase

in 112 day by 11.03%, 19.38% and 35.41% for 10%, 20% and 30% fly ash as

fine aggregate replacement, respectively.

Table 6.9 Flexural strength test of mortar specimens

Mix ID Flexural strength (MPa)

7 day 28 day 56 day 112 day

Ss 6.53 9.34 10.77 10.73

Cs 5.23 8.31 9.75 9.64

Cs+10%FA 5.3 7.44 9.40 8.58

Cs+20%FA 5.18 6.90 7.40 7.78

Cs+30%FA 4.28 5.61 7.18 6.23

Fig. 6.3 Flexural strength of mortar specimens



101

6.5.3. Drying Shrinkage

Fig. 6.4 illustrates the drying shrinkage measurement results of the exper-

iment. Compared to standardized sand, the use of crushed stone sand in mortar

indicates to increase drying shrinkage due to higher water absorption. The uti-

lization of fly ash to replace fine aggregate also indicates to increase drying

shrinkage in age less than 70 days. This behavior was contrary to the drying

shrinkage performance of concrete when fly ash is used as cement replacement.

However, after 70 days, the drying shrinkage of crushed stone sand mortar with

0%, 10% and 20% fly ash as fine aggregate replacement shows similar drying

shrinkage. While 30% fly ash to replace fine aggregate in crushed stone sand

mortar indicates a significant increase in drying shrinkage compared to crushed

stone sand mortar without fly ash.

Fig. 6.4 Drying Shrinkage of mortar specimen



102

6.6. Conclusion

Compressive strength, flexural strength and drying shrinkage of crushed

stone mortar were investigated to characterize the effect of JIS type II fly ash

as low quality fine aggregate replacement the performance of mortar. The

following conclusions are drawn from the test result:

1. The utilization of low quality fine aggregate with high water absorption in

mortar reduces compressive strength and flexural strength, and increases

drying shrinkage compared to mortar made from standardized sand as JIS

R 5201.

2. Replacing crushed stone sand with 10% fly ash shows to improve compres-

sive strength of mortar in early age up to 56 days and gradually increases

and approaching the compressive strength of standardized sand mortar in

112 day by 99.14%. While 20% fly ash as fine aggregate replacement in

crushed stone sand mortar shows to improve compressive strength in early

age day, but indicates lower compressive strength than crushed stone sand

mortar without fly ash in 28 day and 56 day. However, it gradually increas-

es and approaching the compressive strength of standardized sand mortar in

112 day by 99.26%. Furthermore, the compressive strength of crushed

stone sand mortar with 30% fly ash to replace fine aggregate shows reduc-

tion compared to crushed stone mortar without fly ash in less than 56 days.

Nevertheless, it exceeds the compressive strength of crushed stone sand

mortar without fly ash in 112 day strength.

3. As fine aggregate replacement of crushed stone sand in mortar, the use of

fly ash shows reduction in flexural strength. Flexural strength is reduced by

the increased use of fly ash. 10%, 20% and 30% fly ash as fine aggregate

replacement reduced 10.45%, 16.97% and 32.49% of flexural test in 28-day

strength, respectively. This reduction continuous to increase in 112 day by



103

11.03%, 19.38% and 35.41% for 10%, 20% and 30% fly ash as fine aggre-

gate replacement, respectively.

4. The use of fly ash as fine aggregate replacement of crushed stone sand in

mortar indicates to increase drying shrinkage in age less than 70 days.

While after 70 days, the drying shrinkage of crushed stone sand mortar

with 0%, 10% and 20% fly ash as fine aggregate replacement shows similar

drying shrinkage. However, 30% fly ash to replace fine aggregate in

crushed stone sand mortar indicates a significant increase in drying

shrinkage compared to crushed stone sand mortar without fly ash in all ages.

5. By replacing fine aggregate up to 20% with fly ash can improve

compressive strength of crushed stone sand mortar after 56 days and reach

similar drying shrinkage as crushed stone sand mortar without fly ash after

70 days.



104

Bibliography

1. Ahmaruzzaman M, “A review on the utilization of fly ash”, Progress in En-

ergy and Combustion Science, Vol. 36, Issue 3, June 2010, Pp. 327-363.

2. Cao D, Selic E, Herbell JD, “Utilization of fly ash from coal fired power

plants in China”, Journal of Zhejiang University Science A, 2008 9(5), pp.

681-687

3. Joshi RC, Lohtia RP, “Fly Ash in Concrete : Production, Properties and

Uses”, Advances in Concrete Technology Volume 2, Gordon and Beach

Science Publishers, 1997



5. Nath P, Sarker P, “Effect of mixture proportion on the drying shrinkage and

permeation properties of high strength concrete containing class F fly ash”,

KSCE Journal of Civil Engineering, Vol. Issue 6, 2013, pp 1437-1445





cations”, Dissertation, Faculty of the Virginia Polytechnic Institute and

State University, 2002

8. Siddique R, “Performance characteristics of high-volume Class F fly ash

concrete”, Cement and Concrete Research Journal, Vol. 34, 2004, pp. 487-



105

493

9. Limbachiya M, Meddah MS, Ouchagour Y, “Use of recycled aggregate in

fly ash concrete”, Construction and Building Materials Journal, Vol. 27,

2012, pp. 439-449

10. Siddique R, “Effect of fine aggregate replacement with Class F fly ash on

the mechanical Properties of concrete”, Cement and Concrete Research,

Vol. 33, 2003, pp. 539-547

11. Jain A, Islam N, “Use of Fly Ash as Partial Replacement of Sand in Ce-

ment Mortar”, International Journal of Innovative Researce in Science, En-

gineering and Technology, Vol. 2, Issue 5, May 2013

12. Shanmugasundaram S, Jayanthi S, Subdararajan R, Umarani C, Jagadeesan

K, “Study on Utilization of Fly Ash Aggregates in Concrete”, Modern Ap-

plied Science, Vol. 4, No. 5, May 2010, pp. 44-57.

13. Singha Roy DK, “ Performance of Blast Furnace Slag Concrete with Partial

Replacement of Sand by Fly Ash”, International Journal of Earth Sciences

and Engineering, Vol. 4, No. 06 SPL, October 2011, pp. 949-952

106

CHAPTER 7

Conclusion

Great East Japan Earthquake which occurred in March 2011 has brought

great influence to Japan. Not only about the loss of many lives and properties,

but also a number of major issues to be addressed. Massive earthquake that

triggered tsunami has hit Fukushima Nuclear Power Plant has led to the spread

of radioactive substances into the atmosphere, soil, and water. Enormous

amount of contaminated concrete debris from collapse reactor building, and

other structures with high radioactivity need to be disposed. However, due to

the large amount of waste, without proper treatment, landfill and cost required

will be expensive. Therefore, an effective method to reduce radioactive waste,

especially contaminated concrete waste is urgently needed.

In this study, the pulsed power technology is proposed as a decontamina-

tion method by reclaiming aggregate from contaminated concrete waste to re-

duce the volume of contaminated concrete waste. In Chapter 3, a study on re-

duction of radioactive contaminated concrete by the pulsed power technology

is conducted. From this research, it is found that the pulsed power discharge

can be applied as a decontamination method to the radioactive contaminated

CHAPTER 7 Conclusion

107

concrete and reduce the volume of radioactive waste up to 60%. Further, it is

found that coarse aggregate reclaimed from contaminated concrete waste is

predominantly uncontaminated. Therefore it can be reused as recycled aggre-

gate. In addition, 95% of Cs which contaminated the concrete is dissolved in

the treated water in the pulsed power process. Consequently, decontamination

of the treated water used in the pulsed power process is necessary. However,

high concentration of cesium solution is used in this simulation. Therefore, it is

necessary to reevaluate the elution of Cs to water under a condition equivalent

to the actual radioactive contaminated concrete.

On the other side, it is expected that after the Great East Japan Earthquake,

while several nuclear power plant were discontinued, coal-fired power plants

are extensively in service and rapidly expanding to meet the electricity demand.

It means that the amount of fly ash as a by-product of the combustion of coal-

fired power plants should also increase. Hence, the utilization of fly ash to mit-

igate environmental load is needed. Chapter 4, 5 and 6 contain a number of

studies to utilize fly ash and recycled aggregate concrete to promote sustaina-

ble construction.

Chapter 4 evaluates the effect of fly ash as cement replacement on the

strength and drying shrinkage of concrete made from recycled aggregate pro-

duced by the pulsed power technology. It is found that the pulsed power tech-

nology has been proven to reproduce high quality recycled aggregate. Concrete

made from recycled aggregate by the pulsed power technology has similar

quality to natural coarse aggregate concrete in the compressive strength, tensile

splitting strength and drying shrinkage. Further, the use of fly ash as cement

replacement reduces the compressive and tensile splitting strength, and modu-

lus of elasticity both in natural aggregate concrete and recycled aggregate con-

crete. However, it can minimize the drying shrinkage. In concrete made from

recycled aggregate produced by the pulsed power technology, the utilization of


108

fly ash has shown improvement in strength and reduces drying shrinkage.

It is suggested that replacing 25% of cement weight with fly ash in con-

crete made from recycled aggregate by pulsed power technology can re-

duce drying shrinkage without substantial reduction in strength.

As previous studies have reported that two-stage mixing approach in

producing concrete can improve the strength of recycled aggregate con-

crete, Chapter 5 examines the performance of fly ash concrete made from

recycled aggregate by the pulsed power technology with two-stage mixing

approach (TSMA). From that study, it is found that the use of fly ash as

cement replacement reduces the compressive and tensile splitting strength

and modulus of elasticity of recycled aggregate concrete when using both

normal mixing approach (NMA) and TSMA. In recycled aggregate con-

crete without fly ash, TSMA does not show improvement in the compres-

sive strength and tensile splitting strength with same water-to-binder ratio.

Further, in fly ash concrete made from recycled aggregate, TSMA im-

proves the compressive strength and tensile splitting strength compared to

NMA. In the same percentage of fly ash, TSMA shows higher strength

compared to NMA. By replacing 25% of cement mass with fly ash, con-

crete made from recycled aggregate by the pulsed power technology using

TSMA has shown to improve strength without major increase in drying

shrinkage.

To increase the volume of fly ash in concrete, Chapter 6 therefore

evaluates the effect of fly ash as partial replacement of low quality fine

aggregate on the performance of mortar. It is found that the utilization of

low quality fine aggregate with high water absorption in mortar reduces

the compressive strength and flexural strength, and increases drying

shrinkage compared to mortar made from standardized sand as JIS R 5201.

Moreover, replacing crushed stone sand with 10% and 20% fly ash show


109

to improve compressive strength of mortar in early age up to 56 days and grad-

ually increases and approaching the compressive strength of standardized sand

mortar in 112 day. While the compressive strength of crushed stone sand mor-

tar with 30% fly ash to replace fine aggregate shows reduction compared to

crushed stone mortar without fly ash in less than 56 day and gradually increas-

es and exceeds the compressive strength of crushed stone sand mortar without

fly ash in 112 day strength. In crushed stone sand mortar, the flexural strength

is reduced by the increase use of fly ash as fine aggregate replacement. Fur-

thermore, the use of fly ash as fine aggregate replacement of crushed stone

sand in mortar indicates to increase drying shrinkage in age less than 70 days.

While after 70 days, the drying shrinkage of crushed stone sand mortar with

0%, 10% and 20% fly ash as fine aggregate replacement shows similar drying

shrinkage. However, 30% fly ash to replace fine aggregate in crushed stone

sand mortar indicates a significant increase in drying shrinkage compared to

crushed stone sand mortar without fly ash in all ages.

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