MECHANICAL PROPERTIES OF RECYCLED COARSE AGGREGATE ...€¦ · Table 5 Grain size distribution of...

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International Journal of Civil Engineering and Technology (IJCIET)

Volume 10, Issue 09, September 2019, pp. 33-45, Article ID: IJCIET_10_09_004

Available online at http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=10&IType=9

ISSN Print: 0976-6308 and ISSN Online: 0976-6316

© IAEME Publication

MECHANICAL PROPERTIES OF RECYCLED

COARSE AGGREGATE CONCRETE MADE

FROM KNOWN PROPERTIES DEMOLITION

WASTE

Abbas Sadiq Mohammed, Ali Laftah Abbas

Department of Civil Engineering, College of Engineering / University of Diyala,

Baqubah, Daiyla, Iraq

ABSTRACT

In many countries around the world, the demolition wastes disposal represents a

serious problem in sustainable civil engineering structural works since such materials

are accumulated in large quantities some times. When the concerns of cost and

sustainability are considered in the structural design, the use of such waste as an

alternative to some construction materials is highly effective and justified. The basic

objective of this study is to investigate some of the preliminary properties of concrete

made by self-properties controlled recycled coarse aggregate since this issue has a

considerable need to improve knowledge .

Two mix designs are proposed with nominal 20 and 30 MPa compressive strength,

more precisely, the degree of coarse recycled aggregate partial replacement ratio

taken throughout this study as 0 %, 50 % and 100 % respectively using a crushed

concrete casted originally using the same mixes defined.

The results showed that the degree of recycled coarse aggregate decreases in

general performance of the resulted concrete. More precisely, all compressive

strength, modulus of elasticity, splitting tensile strength and modulus of rapture

decreased when such degree progressed. In other hand, workability give a negative

impact when such ratio increased.

Key words: Recycled Coarse Aggregate, Concrete, Mechanical Properties, Degree of

Partial Replacement.

Cite this Article: Abbas Sadiq Mohammed, Ali Laftah Abbas, Mechanical Properties

of Recycled Coarse Aggregate Concrete Made from Known Properties Demolition

Waste. International Journal of Civil Engineering and Technology 10(9), 2019, pp.

33-45.

http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=9

1. INTRODUCTION

As a matter of fact, the urban areas around the word have a progressive need to some

structures like roadways, buildings and bridges, when the old units of these structures are no

longer satisfy their purposes and / or extends its design life periods, replacement or repair



processes are dictated to overcome this situation. As a consequence, there is a considerable

need to more quantities of some construction materials like coarse aggregate. In this way,

alternatives like the recycled coarse aggregate which is mainly results from the concrete

structures demolition process have to be justified to use within this field due to its large

disposal quantities around the world as well as the its cost effectiveness [1].

More precisely, the existence of paste reminders is the main difference between the

normal type and such aggregate which in turn have led to produce more pores in the recycled

aggregate microstructure surface. Due to this concern, the resulted characteristics and

performance can take a wide spectrum of variation according to the origin of such aggregate.

However, this variation may comprise the mechanical behavior ,durability as well as some

important properties like specific gravity, water absorption and density. Because all of above,

research organizations, specifications and researchers are still seeking till now about

improving the knowledge about using this type of aggregate in civil engineering applications

[2].

Additionally, the mechanical properties of concrete made from road waste were studied

in some details in the paste [6].Such properties were also investigated in the presence of the

partial replacement of fly ash and Granulated blast furnace slag [7]. The recycled coarse

aggregate that produced from the construction repair and demolition was also included in

some recent contributions [9, 15], while some of these experimental programs were devoted

to produce high mechanical strength levels of recycled coarse aggregate concrete [9].

Additionally, the resource preservation and environmental concerns of this type of concrete

were also discussed [10] while some other crucial issues like the influence of age and

successive recycling were taken into account [11]. Moreover, some of the scientific research

programs were aimed in the paste to enhance some of the shortcomings like the surface low

quality and performance degradation in the concrete under consideration [12, 13].

However, it can be clearly observed throughout the recent literature that a little amount of

knowledge about the preliminary mechanical properties of recycled coarse aggregate if such

aggregate is made from known properties concrete, thus, this study is trying to cover this

concern by implementing an experimental program.

2. METHODOLOGY

2.1. Materials Used

2.1.1. Cement

Type I of ordinary Portland cement of Tasluoja commercial brand is used in the experimental

program of this study. Tables (1) and (2) list the physical properties and chemical composion

respectively while Table (3) lists the main compounds of such cement.

Table 1 Physical properties of cement used

Physical Properties Test Results* Limits of Iraqi

Specifications No.5/1984

Specific Surface Area (Blaine

Method),cm2/g

298.5 Not less than 230

Setting Time (Vicat Apparatus)

Initial Setting, (min)

final setting, (min)

166

255

Not less than 45

Not greater than 10 hr

Compressive strength, MPa at 3 days

Compressive strength, MPa at 7 days

18.76

26.81

≥ 15.00

≥ 21.00

Soundness (autoclave Method), % 0.35 ≤ 0.8

Mechanical Properties of Recycled Coarse Aggregate Concrete Made from Known Properties

Demolition Waste


Table 2 Chemical composition and main compounds of cement

Compound

Composition

Chemical

Composition Content%

Limits of Iraqi

Specifications

No.5/1984

Lime CaO 62.7 ---

Silica SiO2 18.45 ---

Alumina Al2O3 5.35 ---

Iron oxide Fe2O3 3.64 ---

Magnesia MgO 3.2 <5.00

Sulfate SO3 2.12 <2.80

Loss on ignition L.O.I. 2.96 <4.00

Insoluble residue I.R 0.95 <1.5

Lime saturation

factor L.S.F 0.8 (0.66-1.02)%

Table 3 Main compounds (bougue's equations)

Tricalcium Silicate C3S 67.76

Dicalcium Silicate C2S 1.85

Tricalcium Aluminate C3A 8.02

Tetracalcium alumino ferrite C4AF 11.06

2.1.2. Fine Aggregate

Plate (1) shows the natural sand that used in the present study which brought from Al-Sudour

suburb near Baqubah within Diyala governorate, Iraq. Table (4) lists the physical properties

whereas Table (5) lists the grain size distribution of that sand which is also illustrated in

Figure (1).

Plate 1 Fine aggregate before mixing

Table 4 Physical properties of fine aggregate

Physical

properties Test result

Limits of Iraqi

Specifications

No.45/1984

Specific gravity 2.60 -

Sulfate content 0.11% 0.5% (max)

Absorption 0.75% -

Clay content 2.3 5% (max)



Table 5 Grain size distribution of the fine aggregate

Sieve size

(mm) Passing %

Limits of the Iraqi

specifications No.45/1984 Zone

2

9.5 100 100

4.75 ?:.; 90-100

2.36 ><.8 85-100

1.18 =;.7 75-100

0.60 <:.< 60-79

0.30 92.88 12-40

0.15 7.8 0-10

Figure 1 Grain size distribution curve of the fine aggregate

2.1.2. Course Aggregate

The natural coarse aggregate that wholly used in this study is crushed aggregate with 19 mm

maximum size, during all tests included in this study, the coarse aggregate was cleaned,

washed and air dried before mixing. The physical properties and the grain size distribution are

listed in Tables (6) and (7) respectively.

Table 6 Physical properties of coarse aggregate used

Physical

properties /1984 Test results

Limits of Iraqi

specifications No.45

Specific gravity 2.60 _

Sulfate content 0.08% 0.1% (max)

Absorption 0.70% _

Clay content 0.4% 3% (max)

Table 7 Grain size distribution of coarse aggregate used

Sieve size (mm) Passing by

weight %

Limits of the Iraqi

specifications

No.45/1984

25 100 100

19 100 90-100

12.5 - -

9.5 50 20-55

4.75 0 0-10

2.36 0 0-5

*Sieve analysis was made at soil Laboratory of Engineering College \ Diyala University.

0

20

40

60

80

100

120

0 2 4 6 8 10

Pa

ssin

g %

Sieve diameter in mm

Comulative Passing Lower Limit Upper Limit


Demolition Waste


2.1.3. Recycled Course Aggregate

The physical properties of the RCA used entirely in this study is presented in Table (8) while

its production is illustrated in section

Table 8 Physical properties of RCA

Physical properties 20 MPa 30 MPa

Specific gravity (SSD) 2.45 2.47

Dry specific gravity 2.36 2.4

Absorption 3 % 3.5 %

Loss density kg/m3

7922 79<2

Compact density kg/m3 7;92 7;>2

2.2. Trial Mixes

Actually, series of trials were made to obtain two certain concrete mixes to achieve cylinder

compressive strength 20 and 30 MPa respectively.

Consequently, the mix proportions that were established to get 20 and 30 MPa by weight

are [cement: sand: coarse aggregate] are (1:2.58:3.22) and ( 1 : 1.86 : 2. 63 ) respectively. On

the other hand, these mixes were used to produce the original concrete which then after have

to be crushed to be used as recycled coarse aggregate, finally, such mixes are again followed

to cast the new recycled coarse aggregate concrete with partial replacement 0, 50 and 100 %

recycled coarse aggregate.

2.3. RCA Production

The following sequence was proposed to produce the RCA during the present study:

(4 x 0.4 x 0.1) m normal concrete sections were casted using the same 20 and 30 MPa mixes

of natural aggregate concrete.

• The concrete sections were broken and converted to small pieces.

The small pieces were finally crushed by using a suitable type of traditional aggregate crusher

to produce RCA .

Sieve analyses was finally made to make certain about the produced RCA if it has almost the

same grain size distribution of the natural aggregate then cleaned and washed by tab water

then dried by imposing to sun light for one day and finally packed and stored in laboratory.

2.4. Tested Properties

2.4.1. Los Angeles Test

Los Angeles test is usually used to quantify the degree of pulverization for Natural aggregate

and RCA. During this experimental program, this test was conducted according to ASTM

C131.

2.4.2. Slump Test

Slump test was wholly used to inspect the fresh concrete consistency and to check its

workability for natural and RCA fresh concrete mixes. This tests was conducted during this

study according to ASTM C143.

2.4.3. Compressive Strength (f'c)

The nominal dimensions of the standard concrete cylinders used in the present study are (150

x 300) mm. This test was conducted according to ASTM C39-86, in addition, each reading of



compressive strength represents an average of three. Plate (2) shows the implementation of

this test.

Plate 2 Cylinder during test

In addition, the compressive strength test is used to estimate the modulus of elasticity (Ec)

according to ASTM Designation C469-02, 2002. Dial gages were used to measure the

developed strain in the compressive strength specimens as shown in Plate (3). Ec can be

estimated as follows:

Ec =

(1)

Where:

Ec: Modulus of elasticity, (MPa)

S2: Stress corresponding to 40% of ultimate load, (MPa)

S1: Stress corresponding to a longitudinal strain (0.00005), (MPa)

Ԑ2: longitudinal strain produced by stress S2.

Plate 3 Modulus of elasticity determination


Demolition Waste


2.4.4. Modulus of Rupture (fr)

The modulus of rapture was determined according to ASTM C78-02 standards for the same

proposed mixes and degree of RCA replacement. The prism dimensions used are 100 x 100 x

500 mm and each fr reading represents an average of three. The calculation of the modulus of

rapture is as follows:

fr =

(2)

Where

fr = Modulus of rupture (MPa).

P = Maximum load (N), P/2 applied at 1/3 of the span.

l = Clear span length = 450 mm.

b = Width of specimen (mm).

d = Depth of specimen (mm).

Modulus of rupture test is shown in Plate (4)

Plate 4 Modulus of rupture test

2.4.5. Splitting Tensile Strength (fct)

The splitting tensile strength test was done according to ASTM C496-96 as shown in Plate

(5). The cylinder specimens dimensions are 150 x 300 mm, however, the fct value is

calculated as follows:

fct =

(3)

where

fct = Splitting tensile strength of concrete (MPa).

= Maximum applied load (N).

= Specimen1 diameter1 (mm).

= Specimen1 length (mm).



Plate 5 Splitting tensile test

3. RESULTS AND DISCUSSION

3.1. Los Angles Test

Table 10 Los Angles Test Results

No Normal Aggregate 20 MPa based

RCA. 30 MPa based RCA.

Abrasion (%) 9.1 15.2 16.2

It can be seen from this table that the ratio of abrasion of the RCA is more than the

natural, in the other hand, the compressive strength disparity of the proposed RCA original

mixes is slightly reflected to the ability to resist abrasion. However, aggregate can be used

normally for concrete production if los Angles loss does not exceeds 50 % (ASTM C-33).

3.2. Slump Test

Table 11 Slump Test Results

Mix Type Degree of RCA Replacement Slump mm

20 MPa

0% 90

50% 70

100% 45

30 MPa

0% 80

50% 60

100% 45


Demolition Waste


Figure 2 Variation of slump due to RCA degree of RCA replacement

It can be recognized from the above table that RCA fresh concrete illustrates the expected

very poor nature of workability, which is in turn can be ascribed to the high capability level

to absorb water due to the porous nature of the cement mortar reminders dictated by the

entrapped air in the original RCA mixes .

In addition, for the same degree of RCA replacement, no significant differences between

20 and 30 MPa based RCA workability, however, it is argued that this behavior is due the test

nature and this results are compatible with the information that gained through the literature

[16].

3.3. Compressive Strength

Table (12) views the basic data of the compressive strength test results.

Table 12 Compressive strength Results

Sample No/ RCA% 0% 50 % 100% Mix Type

f'c

in M

Pa

1 21.49 20.66 18.48

20 MPa 2 21.87 19.52 19.2

3 20.? 19.74 19.65

Average 21.2 20 19.1

1 31.7 31.4 28.8

30 MPa 2 31.53 28. 88 28.2

3 30.47 29.81 29.6

Average 31.2 30.03 28.86

It can be noticed from Table (12) that there is a slight difference in compressive strength

when RCA is increased. But on the other hand it can be observed also that the compressive

decreases with such increasing and that can be ascribed to the lack of RCA mechanical

strength, however, this behavior is compatible with recent experience in the literature [17].

3.4. Modulus of Elasticity

Table (13) lists modulus of elasticity results while Figure (3) Shows the variation of Ec due to

the degree of RCA replacement.

0

10

20

30

40

50

60

70

80

90

100

Slu

mp

in

mm

Degree of RCA Replacement %

20 Mpa

30 Mpa

0 50 100

Mix Type



Table 13 Modulus of elasticity results

Sample No/ RCA% 0% 50 % 100% Mix Type E

c in

MP

a

1 22644 21422 20560

20 MPa 2 22735 21015 20890

3 22405 21125 20988

Average 22535 21187 20812

1 28250 27104 25642

30 MPa 2 27974 26211 25188

3 27442 25645 25980

Average 27888 26320 25603

Figure 3 Variation of Ec due to RCA degree of RCA replacement

It is obvious from table (12) that modulus of elasticity of RCA have a general trend to be

lower that of natural coarse aggregate concrete for each mix type, however, it is common that

the modulus of elasticity of the concrete is a function of its components which in turn are

cement past and aggregate [18] and since the modulus of elasticity of cement paste is less than

that of coarse aggregate [19], the RCA concrete will exhibit lower levels of such modulus

because of the presence of cement paste reminders as well as the new quantities. In addition to

that, it is believed that further research is needed to observe the relationship between

compressive strength and the developed modulus of elasticity and their disparity with respect

to the ACI approximation value.

3.5. Modulus of Rupture

Table (14) illustrates the results of modulus of rapture while Figure (4) shows the variation of

fr due to the degree of RCA replacement.

Table 14 Modulus of rapture results


Fr in

MP

a

1 3.5 3.2 3.1

20 MPa 2 3.2 3.1 2.95

3 3.2 3.05 2.84

Average 3.3 3.1 2.96

1 4.8 4.5 4.2

30 MPa 2 4.5 4.2 4.02

3 4.2 4.01 4.01

Average 4.5 4.2 4.17

0

5000

10000

15000

20000

25000

30000

Mo

du

lus

of

Ela

stic

ity

in

MP

a


20 MPa

30 MPa

0 50 100

Mix Type


Demolition Waste


Figure 4 Variation of Modulus of rapture due to RCA degree of replacement

It is clear from Table (14) and Figure (4) that the modulus of rapture of the RCA concrete

is generally lower than the natural, in addition, this trend is more obvious in 20 MPa mix type.

The general lag of such modulus in RCA concrete is compatible with some recent

contributions (Ikeda, 1988), anyways, there is no agreement can absolutely recognized

through the literature about this issue and no clear trend is obvious.

However, another research efforts are justified to discover the degree of relation between

the compressive strength and the relevant modulus of rapture.

4.2.5. Splitting Tensile Strength

Table (15) views the results of splitting tensile strength whereas Figure (5) shows the

variation of fct due the degree of RCA replacement.

Table 15 Splitting tensile strength results


Spli

ttin

g T

ensi

le

Str

ength

in M

Pa

1 2.9 2.8 2.7

20 MPa 2 2.8 2.6 2.5

3 2.8 2.5 2.2

Average 2.83 2.63 2.5

1 3.8 3.4 3.0

30 MPa 2 3.6 3.2 3.1

3 3.2 3.1 2.9

Average 3.5 3.2 3.0

It is obviously shown in Table (15) and Figure (5) that the splitting tensile strength of the

RCA concrete is less than the natural concrete to the both mix types proposed. Actually, weak

bond strength between the cement paste reminders around RCA and the new paste which

exists in the new concrete mix dictates that splitting tensile strength of RCA concrete is less

than natural concrete [21]. Finally, future work is needed to know the degree of relation

between the assessed splitting tensile strength and the consequent compressive strength at the

same circumstances proposed in this study.

0

1

2

3

4

5

0% 50% 100%

Fr

in M

Pa


20 MPa

30 MPa

Mix Type



Figure 5 Variation of fct due to RCA degree of replacement

4. CONCLUSIONS The following conclusions can be made from this study:

Most of the preliminary properties of recycled coarse aggregate concrete illustrate a

clear lack of performance if it is produced using the same mix design of the original

concrete.

Degree of abrasion of the recycled coarse aggregate is higher than natural coarse

aggregate.

For the same degree of replacement, the divergence between the two proposed mixes

compressive strength is not huge.

Further research is needed to investigate the consequent lack in structural members

performance.

Another series of research is needed to investigate that if use the common concrete

admixtures is effective to overcome this lack in performance.

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0

0.5

1

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2.5

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3.5

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Sp

litt

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Ten

sile

Str

eng

th i

n M

Pa


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