International Journal of Engineering and Innovative Technology (IJEIT)

Volume 2, Issue 4, October 2012 

163

A Sustainable Method for Consuming Waste

Concrete and LimestoneKhalid M. Shaheen1, Ehab E. Aziz2

khmshaheen@yahoo.com, ihab_muhanad1988@yahoo.com

Abstract: This research focuses on recycling of waste

concrete and limestone resul ting f rom processing raw l imestone

to render i t suitable for use as bui lding envelopes and decorati ve

purposes. The recycled concrete and limestone were used as

coarse aggregate in concrete mixes. Tests applied on the

resulti ng f resh and hardened concrete were slump, compressive

strength, fl exural strength, splitti ng strength and modulus of

elasticity tests. The data obtained were compared to those of

conventi onal concrete made with natural aggregate using the

same mix proportions. The workabili ty of the recycled concrete

was considerably less than that of natural aggregate concrete

NAC. crushed Limestone aggregate (CLA) and crushed concrete

aggregate (CCA) has absorption r atio of about 14 and 8 times

than that of natural aggregate, respectively. Concrete made with

recycled CLA has a density of 8% less than the reference

concrete or natur al aggregate concrete (NAC) and absorption at

about 74% greater than NAC. Concrete made with recycled CCA

has density 97% than that of NAC and absorpti on at about 54%

greater than NAC.

I ndex Terms  —   D&C waste, Recycling, concrete waste,

limestone waste.

I.  INTRODUCTION

Recycling is the act of processing the used material for

use in creating new product. The usage of natural

aggregate is getting more and more intense with the

advanced development of the infrastructures. In order to

reduce the usage of natural aggregate, recycled aggregate

can be adopted as the replacement materials. Recycled

aggregate are comprised of crushed, graded inorganic

 particles processed from the materials that have been used

in the constructions and demolition debris. These

materials are generally from buildings, roads, bridges,

and sometimes even from catastrophes, such as wars and

earthquakes.

With the sharp development of construction and

increase of people’s awareness of environmental

 protection, waste control and management becomes one

of the great challenges of modern society for the mission

of sustainable development. Construction and demolition

(C&D) waste constitutes one major portion of total solid

waste produced in the world, including demolished

concrete, bricks, and masonry, limestone, ceramic and

other materials. The environmental protection agency

EPA defines the C&D debris as “waste material that is

 produced in the process of construction, renovation, or

demolition of structures. Structures include buildings of

all types ,both residential and non-residential, as well as

roads and bridges. Components of C&D debris typically

include concrete, asphalt, wood, metals, gypsum

wallboard and roofing” [1]. The growth of population on

the planet earth necessitates the construction of more and

more buildings. The increasing quantity of C&D waste

leads to the increase of loads on landfills. Large numbers

of countries, especially developed ones, suffer from

inefficient waste management. For example, in one of the

 big Brazilian cities only 20% of civil construction waste

is collected by companies licensed by public authorities,

and only 1% of the waste collected in 2004 by authorized

companies went to solid waste landfill of the city [2].

Demolition works in Kuwait was reported to produce

about 600×103  tons of C&D wastes annually at an

average rate of about 1.5 tons/m2 of building area [3].

Mosul city (Iraq) suffers from increasing quantities of

D&CW. Waste collected by Mosul municipality was

estimated to be 182×103, 178×10

3, and 598×10

3  m

3  for

the years 2009, 2010, and 2011, respectively. Mosul city

doesn't have landfill facility for waste disposal but it is

dumped in remote suburbs. Some of these wastes are used

for swamps filling near residential areas [4].

Three approaches can be employed for project waste

reduction. The first is to look for ways waste can be

 prevented by identifying potential waste early in the

design process. The second is to identify waste that can

 be salvaged for reuse, and the third approach is to figure

out which waste materials can be recycled [5]. The

developed world has recognized the importance of such

strategies and developed ways to consume the waste. The

European Demolition Association estimates that out of

the 200 million tons of waste produced annually in

Europe, about 30% of this quantity is currently being

recycled [6]. Japan is a leading country in recycling

concrete waste, with 100 % recycling of the wastes that

are used for new structural applications. The recycling

rates of various types of C&D waste there for the years

1995, 2000, and 2003 were 65%, 96%, and 98%,

respectively [7].

The nature of building in Mosul city is distinguished

with using concrete as main construction material.

Concrete blocks are widespread in construction as bearing

wall or even partitions. The availability and cheapness of

concrete constituents made it the most famous material

compared to other construction materials. This means that

most of D&C wastes in Mosul city are composed of

concrete. Recycling process is the most important method

for consuming the waste and protects the environment.

There are different methods to recycle waste such as

using it as sub-base in roads, in filtrations layers, in

asphalt pavement or in concrete. Tests showed the ability

of using recycled coarse aggregate at self consolidating

concrete with optimum content up to 50% of NA [8].

 

 164

Limestone is a familiar construction material in the city

of Mosul since the Assyrian civilization. Nowadays,

limestone is mainly use as decorative material for

different types of buildings, mainly residential ones. The

sources of limestone waste are the construction waste,

demolition waste, and raw limestone processing. Most of

the limestone waste is generated during cutting large

stone to smaller desired shapes. As much as one-half of

quarried stone may become waste during fabrication [9].

About 80 Limestone processing mills are spread at the

left side suburbs of Mosul city [10]. Limestone dust can

 be used as an additive in concrete mixes to improve the

strength of concrete at late ages [11]. Limestone can be

used in concrete as coarse aggregate in places exposed to

chemical attack or without [12].

This paper investigates recycling of waste concrete and

limestone as coarse aggregate at certain percentages in

concrete instead of natural aggregate. Studying the

 properties of recycled aggregate and the concrete.

Produced is the other goal of the present study.

II.  METHODOLOGY

A. Materials:

1.Crushed concrete aggregate (CCA):

Concrete is a widespread building material in Mosul

city. It is used in slabs, columns, building blocks,

 pavements and other applications. Waste concrete used in

this study was a mix of beam, column, slab and pavement

concrete. The samples collected was crushed, sieved, and

then washed. The size of aggregate ranged between 5  –  

20 mm. Fig.1 shows a sample of the waste concrete

 before crushing. Fig. 2 depicts the construction and

demolition wastes near a swamp.

Fig. 1: A Sample of Waste Concrete

Fig. 2: Dumps of Demolition and Construction Waste

2. Crushed limestone aggregate (CLA):

The industrial district in the city of Mosul contains

huge dumps of waste limestone which appear as a by-

 product from processing of raw limestone, Fig. 3.

Processed Limestone is usually used in the finishing

works of building envelopes as decorative materials.

Fig. 3: A waste Limestone dump

Samples of waste limestone were collected and crushed

to convert it to coarse aggregate with maximum size of

20mm and minimum size of 5mm. Fig. 4 shows the

crushed limestone aggregate used in this study.

Fig. 4: Crushed limestone aggregate

3. Natural coarse aggregate (NA): 

The natural coarse aggregate used was river bed gravel

obtained from River Dijla (Mosul/Iraq). This gravel was

 prepared to have the same size range as CCA and CLA. 

4. Fine aggregate (sand): 

Sand used in this study was natural sand supplied from

Kanhash region (Mosul). This type of sand is known for

its good grading according to the BS 882 limits. Fig. 5

shows the sieve analysis of this sand.

Fig. 5: Grading Curve of the Sand

 

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5. Cement:

The binding material used was ordinary Portland

cement produced by Sinjar Factory (Mosul). Table 1

shows the Chemical composition of the cement used [13].Table 1: Chemical Composition of Portland cement Used

in the Study.

Main Oxides %

CaO 64.06

SiO2  19.99

Al2O3  6.32

MgO 2.75

Fe2O3  2.8

SO3  2.06

6. Water:

Tap water was used for concrete mixtures as a medium

for cement hydration. The water was free from impurities

that could adversely affect the properties of the resulting

concrete.

B. Methods:

1. Mix Proportion, Casting and Curing:

A predetermined compressive strength of 34 MPa was

decided for the resulting concrete at age of 28 days.

Accordingly, the mix proportions obtained through ACI

mix design method were (1: 1.8: 2.4) with water cement

ratio W/C ratio of 40%. The cement content of the mix

was 417 kg/m3. Fresh concrete has casted in cast iron

molds immediately after mixing in a batch mixer for 3

minutes followed by 3 minutes rest, then another 2

minutes mixing. Samples were then cured with water at

temperature of 23 ± 2 according to ASTM (C 511).

2. Aggregate tests:

Several testes were applied to the aggregate according

to ASTM such as specific gravity and absorption (C 128)

for fine aggregate, and (C 127) for coarse aggregate.

Voids ratio and bulk density(C 29), and clay content (C

117).

3. Concrete Tests:

A concrete mix of 100% NA was used as the reference

mix or natural aggregate concrete (NAC). Other five

mixes were made with replacement percentage of 25%,

50%, 75%, and 100% between crushed concrete and

limestone, Table 2 shows list the type of mixes. All mixes

were prepared with the same mix proportions of (1: 1.8:

2.4). The volume of CCA and CLA was equal to that of

 NA.Table 2: Type of Mixes

Mix samples

Natura

l

aggregate

(NA)

Crus

hed

concrete

(CCA)

Crush

ed

limestone

(CLA)

N

AC

A

(Reference)100% - -

R 

AC

B - 100% 0%

C - 75% 25%

D - 50% 50%

E - 25% 75%

F - 0% 100%

The fresh concrete was tested for slump value.

Compressive strength, flexural strength, splitting strength,

modulus of elasticity, density, and absorption tests were

applied on hardened concrete. The tests were conducted

according to ASTM and BS.

3.1. Slump test:

Slump test was conducted to determine the workability

of fresh concrete. The test was according to the ASTM

(C143).

3.2 . Compressive strength test:

British standard BS 1881: Parts 116 was used as a

guide for testing the compressive strength of the hardened

concrete. The concrete cubes were tested at ages of 7, 14,

28, and 56 days for each of NAC and RAC. Cube

dimensions were 100mm × 100mm × 100mm.

3.3. Flexural strength test:

Flexural strength was determined according to ASTM

(C 78) using simple beam with third point loading. Test

 beam dimensions were 100mmX 100mm X 400 mm.

3.4. Splitting strength test:

Splitting  strength was tested according to ASTM (C

469). Cylindrical sample with dimensions of 100mm×

200mm were used. Samples were tested at age of 28 days.

3.5. Modulus of elasticity:

A Cylindrical samples with dimensions of 150mm ×

300mm were used for modulus of elasticity determination

for both NAC and RAC at age of 28 days as for ASTM

(C 469).

III.  RESULT AND DISCUSSIONS

A. Aggregate tests:

Table 3 presents the results of tests applied on the

aggregate used in the mixes. All tests were performed in

accordance with ASTM specification.Table 3: Aggregate tests results

TestsN

ACCA CLA

Sa

nd

Specific

Gravity

(SSD.)(kg/m3)

26

902439 2172

263

0

Bulk dry

density (kg/m3)

16

59

1349

.2

1174

.3

189

1

Absorption

(%)

0.6

7

5.44

89.89 2

Voids (%)37.

841.5 40.4

26.

5

Clay (%)0.2

5- - 0.8

Comparing CCA to NA it can be found that the CCA

has less specific gravity, less bulk density, and more

water absorption. The same findings of the comparison

were reached by Radonjanin et al (2010) [14], Abed

(2009) [15], and Obla et al (2007) [16]. The results of the

specific gravity at SSD condition show that the NA has a

specific gravity greater than that of CLA, and CCA by

about 24% and 10%, respectively. A bulk dry density of

 

 166

CLA represents about 71% of that of NA, and about 81%

of that of CCA. The absorption values of CLA and CCA

are estimated to be about 14 times and 8 times than that

of NA, respectively. The voids ratio in the NA was

slightly less than that found in both CCA and CLA.

B. Slump values:

The slump value for the NAC was higher than that of

RAC. Fig. 6 shows the slump test performed.

Fig. 6: Slump Test

The values of slump test for the six mixes are shown in

Fig. 7.

Fig. 7: Results of Slump Test

The slump indicates a decreasing trend of workability

when the percentage of recycled aggregate is increased,

similar trend was found by Nelson et al (2004) [17], and

Arum (2011) [18]. Slump value is directly proportional to

the density, and inversely proportional to the texture [19].

CLA and crushed CCA are lighter in weight and rougher

in texture than natural aggregate. Roughness obstructs

flow ability of concrete; therefore, the slump value of

RAC was less than that of NAC. Low slump value makes

the casting process more difficult. Raising the slump

value needs more compaction or more W/C ratio.

Increasing the W/C ratio may have bad effects on the

 properties of the resulting concrete.

C. Compressive strength values:

It is observed that there is no much difference between

reference mix A and mix B. The difference at age of 28

days was 6.8%, then it got decrease at subsequent ages.

This means that the CCA results in good compressive

strength properties. The compressive strength of mix A

was found to be 25.4% - 36.2 % greater than that of mix

F. This suggests that CLA reduces the strength of

concrete, as shown in Table 4. The greatest difference

was noticed at early ages. The difference in strength has

then become lower until it was 25.4% at the age of 56

days. Figure 8 shows the strength development of various

mixes through ages progress.

Table 4: Summary of Compressive Strength Test  

Fig. 8: Compressive Strength Development with Age of

NAC and RAC

There was no significant variation in strength of

concrete made from NA and CCA. Similar results were

obtained by limbachiya (2004) [20]. Some studies found

that of CCA tend to reduce the compressive strength of

the resulting concrete [16]The compressive strength

obtained from the test was clearly more than that already

 been determined through mix design. This could be

attributed to the use of 100mm×100mm×100mm cubes

instead of cylindrical molds. Small cubes result in a

compressive strength higher than that obtained from

cylinders [19].The strength obtained for RAC is suitable

Age

(days) 

Compressive strength of mixes (MPa) 

A B C D E F

7  48.6 45.3 43.5 42.4 35.8 31

14  51.3 48.2 45.2 44.5 39.1 36.9

28  54.4 53.4 48.1 47.9 43.3 38.7

56 56.6 55.1 52.7 49.8 46.5 42.2

 

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for structural application. Figure 9 depicts a cube during

and after the test.

(a) A Cube of RAC during the Compressive Strength Test

(b) A Cube of RAC after the Compressive Strength Test

Fig. 9: A Cube of RAC during and after the Compressive

Strength Test (a, and b)

D.  Flexural strength:

The flexural strength obtained for RAC is less than that

of NAC. The difference in strength with mix B do not

exceed 2%, but the mix F a flexural strength of about

24% less than that of NAC. Figure 10 shows the variation

 between the mixes in this respect.

Fig. 10: Flexural strength test at 28 days

Fig. 11 Shows a RAC Beam during and after Flexural

strength test.

(a) A beam of RAC during the flexural test

(b) A beam of RAC after the flexural test

Fig. 11: A Beam of RAC during and after the Flexural

test (a, and b)

E. Splitting strength:

The results reveal that the splitting strength of NAC is

more than that of RAC with reduction percentage about

5% and 40% for CCA and CLA, respectively. Fig. 12

shows the values of splitting strength for the six mixes.

 

 168

Fig. 12: Splitting strength tests at 28 days

Fig. 13 shows halves of cylindrical samples A, B, C, D,

E, and F after failure by splitting test.

Fig. 13: Halves of Cylindrical samples of NAC and RAC

after Splitting Test

F. Density:

The hardened concrete shows that the density of CCA

in mix B was less than that of NAC, and CLA in mix F

was lighter than all samples shown in Fig. 13. The density

of RAC is less than that of NAC, and the density reduces

 by increasing the limestone percentage. It can be

observed that the density of RAC in mix F is about 92%

of the NAC density. This is because the CLA is lighter

than NA of about 29% by weight, and the CCA is lighter

than that of NA of about 13%. CCA is decreasing the

density [14, 15]. Fig. 14 illustrates the densities of six

concrete mixes.

Fig.14: Densities of the Six Mixes Involved in the Study

The density of lightweight concrete not exceed 1840

kg/m3  [19], therefore, the (RAC) used could not be

consider as lightweight concrete.

G. Absorption of hardened concrete:

The absorption of RAC is higher than that of NAC as

shown at Fig. 15. This is because the absorption of CLA

and CCA is greater than that of NA, review Table 2.

Fig. 15: Absorption of The Six Mixes Involving in The

Study

Recycled aggregate was increasing the absorption of

concrete more than that of NAC. Absorbed water was

 proportionally increased with increasing recycled CLA

content, but such variation was reduced in mixes (D, E,

and F). The CCA is increasing the absorption of concrete

[14, 15]. Absorption ratios of RAC for the mixes B to F

samples is ranged between (6.64% - 7.5%) compared to

mix A. Mix A has an absorption ratio of 4.3%.

H. Modulus of elasticity:

The modulus of elasticity test indicates a decrease in

modulus of elasticity when recycled aggregate was used.

It was observed that CCA reduces the modulus of

elasticity, and the trend of modulus of elasticity value

inversely proportional to the replacement percentage of

limestone. The modulus of elasticity of concrete also

decreases with increasing CCA. Similar results were

obtained by Rdonjanin (2011) [14], and Nelson et al

(2004) [17].  Fig. 16 shows stress-strain curve for NAC

and RAC.

Fig. 16: Modulus of Elasticity Test (Stress-Strain Curve)

 

 169

Figure 17 shows the apparatus used for the

determination of modulus of elasticity before and during

the test.

Fig. 17: Modulus of Elasticity Test

IV.  CONCLUSION

The following conclusions could be reached through

the results of the experimental works carried out in this

research:

1.  Recycled aggregate concrete has good strength

about 53.4 MPa for mix with 100% crushed concrete

aggregate and 38.7 MPa at mix with 100% crushed

limestone aggregate at 28 days.

2.  The crushed concrete aggregate is lighter than

that of natural aggregate, but crushed Limestone

aggregate was the lightest of them. This property may

result in less dead load in building.

3.  The strength of concrete with 100% limestone

aggregate lower than that of natural aggregate concrete

for the same mix proportion. Variation in strength ranged

 between 25.4% - 36.2% through the ages 7 - 56 days.

4.  Slump of recycled aggregate concrete is less

than that of natural aggregate concrete. The slump is

inversely proportional with the limestone aggregate

which shown very poor slump.

5.  The absorption in mixe with 100% crushed

concrete aggregate and other mix with 100% crushed

limestone aggregate greater than that of reference mix

with 100% natural aggregate concrete at about 54% and

74%, respectively.

6.  Recycled aggregate concrete reduces the

modulus of elasticity. The crushed limestone aggregate

reduces the modulus of elasticity according to its

 percentages when used in concrete.

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