International Journal of Civil Engineering and Technology (IJCIET)
Volume 10, Issue 04, April 2019, pp. 1901–1912, Article ID: IJCIET_10_04_199
Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJCIET&VType=10&IType=4
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
© IAEME Publication Scopus Indexed
Mohamed Husain
Professor of Concrete Structures, Department of Civil Engineering,
Faculty of Engineering, Zagazig University, Zagazig, Egypt
Khaled Fawzy
Associate Professor of Concrete Structures, Department of Civil Engineering,
Faculty of Engineering, Zagazig University, Zagazig, Egypt.
(Currently He is the Head of Construction Engineering Department, Delta - University)
Khaled Fawzy Kotb
Demonstrator, Department of Civil Engineering,
Faculty of Engineering, Sinai University, North-Sinai, Egypt.
ABSTRACT
The topic of recycling concrete waste is significant in the general effort for prospective growth and environmental conservation in our time. Therefore, the use of recycled concrete aggregate as an alternative to natural coarse aggregate in concrete mixes is an essential solution for preserving the natural aggregate resources and saving landfill spaces. This paper's main goal is to assess the mechanical properties of recycled aggregate concrete with target strength 30Mpa after 28 days at different replacement ratio and to improve its behavior by adding steel fiber. The main parameters of this study are recycled concrete aggregate ratio and steel fiber content.
Sixteen concrete mixtures are designed with different RCA ratio (0%, 30%, 70%, and
100%) and hooked steel fiber (0%, 0.5%, 1%, and 1.5%) by volume at fixed (W/ C ratio=0.4). The results showed that the mechanical property of RAC decreases gradually with increasing RCA ratio compared to control mixes. Nevertheless, the results ameliorate with increasing the content of steel fiber.
Key words: Recycled aggregate- (RCA) Recycled aggregate Concrete-Compressive strength-
Tensile Strength-Steel fiber
Cite this Article: Mohamed Husain, Khaled Fawzy and Khaled Fawzy Kotb, Sway of Steel
Fiber and Recycled Aggregate Content on Mechanical Properties of Recycled Aggregate
Concrete, International Journal of Civil Engineering and Technology 10(4), 2019, pp. 1901–
1912. http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=4 http://www.iaeme.com/IJCIET/index.asp 1901 editor@iaeme.com

Mohamed Husain, Khaled Fawzy and Khaled Fawzy Kotb
Concrete is the most known material, which has been utilized as a piece of all fields of development. It is worth mentioning that the concrete consumption occupies the second highest level of consumption material in the world subsequent to water. Massive quantities of concrete wastes are produced annually due to reconstructing of old structures, repair works and wastes result from common destructive phenomena (quakes and winds) [1, 2 and 3].
Empty lands for storing these wastes are scarce, particularly in urban areas. It is notable that concrete comprises of natural coarse aggregate what's more this is the fundamental segment of concrete, fine aggregate, water, and cement. Wherefore, because of the fast increment in the generation and utilization of concrete, this requires gigantic amounts of natural aggregates. It was necessary to look for an alternative by recycling concrete wastes and obtaining RCA. Therefore, the recycling of these concrete rubbles is the most known approach to dispose of these wastes. In addition to producing a new aggregate utilized as partial or total replacement for NA in concrete mixes, reduction in environmental pollution, dump sites and saving in natural aggregate resources. The RCA can be characterized as crushed concrete consists of small parts of aggregate coated with cement paste from the dumps of old structures that has been processed to produce aggregate suitable to use in new environmentally friendly concrete. Due to the frailty of RCA. The applications of RCA were restricted to use in nonstructural applications such as sub -base in road construction, plain concrete, bank protection, soil stabilization and fill behind retaining walls [4,5,6]. So, the usage of recycled concrete aggregate in structural applications have an unfavorable effect on their mechanical and structural behavior such as bond strength, compressive strength, flexure strength, and shear strength. RCA has some imperfections that negatively affect the physical and mechanical properties of concrete. Imperfections such as high water absorption up to 6 % lead to lower workability for fresh concrete, low specific gravity, high dry shrinkage and creep. Also, low compressive strength, tensile strength, flexure strength and modulus of elasticity [1,4]. In order to improve the performance and durability of RAC, steel fiber was added to the concrete.
In this section, we shall mention the previous analytical studies to study the physical and mechanical characteristics of RAC and the influence of adding steel fiber on improving RAC performance. In terms of formalism characteristics, RAC less suitable than natural aggregate.
Singh.R and Singh.J [7] reported that recycled aggregates have characteristics different from the NA of these physical properties that RCA are more angular, harsh (rough) surface texture, elongated particles, and more porous and high rate of water absorption. This is due to the layer of cement involved to the granules [8, 9]. Hence unfavorably influencing on the workability of the concrete and requires a lot of water to reach the appropriate workability.
Rao. A et al. [10] expressed that the water absorption of recycled coarse and fine aggregates ranges from 3% to 12%, which is depended on the sort of concrete used for producing the aggregates. While the value of absorption for NA not exceed from 0.5% to 1%, which is much lower than RA. Wagih.A.M et al. [11] reported in their study on RCA from 15 different demolition and landfill locations around Cairo. The water absorption of RCA ranged from
2.15% to 7.15%. While the water absorption restrain for NCA is 2.5%, according to ECP 203-
2008. Many researchers have signposted that there is a reduction in the compressive strength of RAC. This reduction depends on some parameters; the quality of aggregates (high, medium and low strength), replacement ratio, water/cement ratio, the moisture condition of the RA, the strength of the cement matrix, the interfacial bond between the cement matrix and the aggregates, round shape, smoother texture and the presence of a large percentage of fine http://www.iaeme.com/IJCIET/index.asp 1902 editor@iaeme.com

Sway of Steel Fiber and Recycled Aggregate Content on Mechanical Properties of Recycled
Aggregate Concrete particles in concrete mix [12,13]. Ismail Abdul Rahman et al. found in their study that the compressive strength of RAC is lower than NAC by 10%when compared the compressive strength of concrete made of RA and NA with different aggregate sizes 10, 14 and 20 mm
[13]. Poon. et al. found recycled aggregate concrete has a higher compressive strength. They commanded that recycled aggregate has shape that is more angular and rough surface texture compare to natural aggregate. The angular shape and rough texture of RA leads to enhancing the bond and strength of concrete. To increase the compressive strength, RA should be the oven-dried condition that will produce the interfacial bond between cement paste and aggregate particles [14]. The compressive strength of recycled concrete powerfully depends on the water–cement ratio of the original concrete. For the same water–cement ratio for both the original and the recycled concrete, the strength of new concrete will be improved compare to the original strength, and vice versa [15]. The addition of a plasticizing, an air entraining, a retarding, and an accelerating admixture to the original concrete has small or no impact on the compressive strength of RAC [16]. Ahmed Md. S and Vidyadhara H. S studied the effect of
RCA on compressive strength, this by finding the optimum RCA replacement ratio to NCA in concrete mixture to get the target strength 20Mpa after 28 days, the RCA ratios were 0%,
20%, 40%, 60%, 80%, and 100%. The results showed significant decrease in compressive strength whenever RAC ratio is increased. The compressive strength has dropped about
5.14% at 20% RAC even up to 10.79% at 60% RAC. The maximum reduction was 29.11% for 100% RAC replacement ratio. From the above, they found that the optimum percentage of replacement of recycled aggregate by natural aggregate is 60%, which meets the required strength [17]. As RCA replacement ratio, water cement ratio (W/C) and amount of mortar attached to aggregate granules were increased, the value of the modulus of elasticity decreased by (30-50) % of traditional concrete and the ratio of the flexural and the splitting strengths to the compressive strength is in the range of 16–23% and 9–13%, respectively.
These results are lower comparing to the recommendations of ACI 363R by 10– 15% [10, 17,
18]. The effect of adding steel fibers to RAC improved the mechanical properties to an acceptable extent; the results showed that the addition of steel fiber to RAC leads to reduction in workability. Also by increasing of steel fiber ratio from 0% to 1.5% by volume of concrete led to increasing in compressive strength, splitting tensile strength and flexure strength by
25%, 28% and 23% respectively [2]. Krishna T. S investigated the behavior of RAFRC by using various RA replacement ratio (0%, 25%, 50%, 75%, and 100%) and a steel fiber ratio
(0%, 1%, 1.5%, 2%) for concrete with target strength 20 Mpa. Cubes of size 150*150*150 mm and beams of size 150*150*600 are casted and tested at 7 and 28 days. The results demonstrated that the distinctions of strength of specimens obtained by replacement of RA with NA with addition of steel fiber in different proportions are somewhat satisfactory. The compressive strength and flexural strength of cubes and cylinders after 28 days ranged from
41.46 to 29.3N/mm2 and 4.51 to 3.91 N/mm2 sequentially with RA replacement ratio, in the range 25 to 100% with steel fiber from zero to 2%. Therefore, the researcher recommended that the percentage of replacement not exceed 25% in addition to the maximum values of compressive strength and flexural strength obtained at 25% RA and 2% of steel fiber as follow 41.46N/mm2 and 4.51 N/mm2. Therefore, the usage of steel fiber with RA has a great benefit to increase the strength of concrete. [19] http://www.iaeme.com/IJCIET/index.asp 1903 editor@iaeme.com

Mohamed Husain, Khaled Fawzy and Khaled Fawzy Kotb
3.1. MATERIALS

The water used in mixing the tested specimens is tap water that was clean, and drinkable.

The fine aggregate is natural siliceous sand. it was relatively clean from harmful substances.
The physical properties of using sand and sieve analysis are shown in Table 1, Table 2 and
Figure 1 respectively.

The utilized coarse aggregate divided into:
NCA: natural crushed stone (Dolomite) having fineness modulus of 3.93 and a water absorption 0.94
%.
RCA: the recycled coarse aggregate produced from crushing of old concrete elements casted in laboratory and had known strength ranging from (40-60) MPa. The physical properties of RAC were showed in Table 3. The sieve analysis of NCA and RCA were showed in Figure 2.

Super- plasticizer supplied by SIKA EGYPT for construction chemical company, under the brand name ViscoCrete3425 as shown in Figure 3 was used to improve the workability of
RAC. Its specific gravity was 1.08 t/m3 without any chloride content and it was compatible to all kinds of Portland cement. The used super –plasticizer conforming to (BS EN 934 part2:
2001) and (ASTMC494) Type G and F.

Steel fiber have clear, bright and loose surface with hooked end anchorage which is free from rust and oil as shown in Figure 4. The aspect ratio l/d equal to 62.5 and tensile strength
1000N/mm
2
. The geometric properties of steel fiber are shown in Table 4.
3.2. Mix Proportion
The amounts of components of concrete mixes per 1m3 are calculated through the absolute volume method as in Table 5. The concrete mixes were designed to get target compressive strength of 30 MPa after 28 days. This study comprised of 16 mixes that are divided into four groups and carried out at the same laboratory conditions. The four groups had the same W/C ratio of 0.4. The difference between them was in RA replacement ratio (0%,30%,70%,100%) and steel fiber content (0%,0.5%,1%,1.5%) by volume. The first group represent the control mixes, which consist of NA only and steel fiber; however, in the other three groups, the natural aggregate replaced by RA variably as mentioned before with the same values of steel fiber. The water absorption of the used RCA equal to 4 times the absorption of NCA.
Therefore, the RCA was immersed in water for 24 hr. then dried in wet cloth until it reaches the degree of saturation with water and does not effect on water content in mixes. Fine and coarse aggregates were mixed on dry for 30 second then cement was added to the mixture and was left for another 30 seconds then was adding water to mix.
Table 1 Physical properties of FA
Property Value
Specific weight (t/m
3
) 2.65
Volumetric weight (bulk density) (t/m
3
) 1.60
Sieve size (mm)
Weight Retained (gm)
Percent Retained (%)
Percent Cumulative (%)
Passing (%)
Table 2 Sieve analysis of FA
2.5
314
10.47
10.47
89.53
1.25
916
30.53
41
59
0.6
1613
5.23
53.77
94.77
0.3
135
4.5
99.27
0.73
0.15
22
0.73
100
0 pan
3000
100
345.51
154.49
http://www.iaeme.com/IJCIET/index.asp 1904 editor@iaeme.com

Sway of Steel Fiber and Recycled Aggregate Content on Mechanical Properties of Recycled
Aggregate Concrete
Table 3 Physical properties of RCA
Property
Specific weight (t/m3)
Volumetric weight (bulk density) (t/m3)
Water absorption %
Void ratio %
Value
2.5
1.31
3.9%
49.9%
Table 4 Geometric properties of steel fiber
Length (L) Diameter(D)
50mm(+/-
3mm)
0.8mm
Aspect ratio
(L/D)
62.5
Middle length
(ML)
40mm(2/-3mm)
Height of hook (HH)
2.10-
2.90mm
Height of hook
(HL)
4-60mm http://www.iaeme.com/IJCIET/index.asp 1905 editor@iaeme.com

Mohamed Husain, Khaled Fawzy and Khaled Fawzy Kotb
RCA00
RCA00F5
RCA00F10
RCA00F15
RCA30
RCA30F5
RCA30F10
RCA30F15
RCA70
RCA70F5
RCA70F10
RCA70F15
RCA100
RCA100F5
RCA100F10
RCA100F15
Mix
160
160
160
160
160
160
160
160
160
160
Water
(W)
(kg)
160
160
160
160
160
160
Figure 7 A flexure testing machine
Table 5 Shows the mix proportion in (kg/m
3
)
Cement(C)
(kg)
Sand(S)
(kg)
CA (kg)
NCA RCA
Steel fiber Super – plasticizer(S.P) (liter)
400
400
400
400
400
400
400
400
400
400
400
400
400
400
400
400
676.047
676.047
676.047
676.047
676.047
676.047
676.047
676.047
676.047
676.047
676.047
676.047
676.047
676.047
676.047
676.047
1216.88
851.816
365.064
0
0
365.064
851.816
1216.88
0
43.175
87.135
130.7
0
43.175
87.135
130.7
0
43.175
87.135
130.7
0
43.175
87.135
130.7
3.2
3.2
3.2
3.2
All tests in this research were prepared in the construction material laboratory in civil engineering department, faculty of engineering, Zagazig University, Egypt. All specimens were tested according to the Egyptian code of practice.
4.1. Compressive Strength
4.1.1. Effect of RCA replacement ratio
Figure8 shows the relation between 7 and 28 days' compressive strength and recycled concrete aggregate replacement ratio. As mentioned before, the recycled concrete aggregate has been added by proportions 30%,70% and 100% where the increase of RAC content at constant Water/Cement ratio (W/C=0.4) leads to depression in compressive strength with respect to samples with NA. The impact of RA content on compressive strength shown in
Fig.9 detects a decrease in compressive strength of 6.48%,12.13 and 14.98% at RCA ratio
30%,70% and 100% respectively. Fig.8 also shows that the compressive strength at 7 days approximately equals 81% of the compressive strength at 28days. respectively. Figure 8 also http://www.iaeme.com/IJCIET/index.asp 1906 editor@iaeme.com

Sway of Steel Fiber and Recycled Aggregate Content on Mechanical Properties of Recycled
Aggregate Concrete shows that the compressive strength at 7 days approximately equals 81% of the compressive strength at 28days .
40
35
30
25
20
15
10
5
0
36.59
29.33
34.22
27.70
32.15
25.04
31.11
23.70
RCA00 RCA30 RCA70 RCA100
Replacement ratio
%
Fcu after 7days Fcu after 28days
Figure 8 Compressive strength at 7and 28 days
38
36.59
36
34
34.22
32
30
32.15
31.11
28
RCA00 RCA30 RCA70 RCA100
Replacement ratio %
Fcu after 28days
Figure 9 Effect of RCA replacement ratio on compressive strength
4.1.2. Effect of steel fiber content
As mentioned before, the steel fiber content was added with percentage 0.5%, 1%, 1.5% by volume. Fig.10 shows a relation between 7 and 28 days' compressive strength for samples with natural aggregate and steel fiber content. It was shown that for 0.5%, 1%, and 1.5%by volume steel fiber content the increasing of the 28 days' compressive strength with respect to samples without steel fiber was 5.68%, 9.73%, and 17.41%. Fig.11 shows a relation between
7 and 28 days' compressive strength for samples with 30%RCA and steel fiber content. It was shown that for 0.5%, 1%, and 1.5%by volume steel fiber content the increasing of the 28 days' compressive strength with respect to samples without steel fiber was 8.24%, 11.25%, and
14.29%. Fig.12 shows a relation between 7 and 28 days' compressive strength for samples with 70%RCA and steel fiber content. It was shown that for 0.5%, 1%, and 1.5%by volume steel fiber content the increasing of the 28 days' compressive strength with respect to samples without steel fiber was 7.37%, 12.66%, and 17.51%. Also, Fig.13 shows a relation between 7 and 28 days' compressive strength for samples with 100%RCA and steel fiber content. It was shown that for 0.5%, 1%, and 1.5%by volume steel fiber content the increasing of the 28 days' compressive strength with respect to samples without steel fiber was 6.2%, 11.44%, and
G1: RCA 0% (Control Mix) G2: RCA30% http://www.iaeme.com/IJCIET/index.asp 1907 editor@iaeme.com

Mohamed Husain, Khaled Fawzy and Khaled Fawzy Kotb
13.82%. Proving for the above Nguyen Van CHANH reported that adding of fiber to the concrete has a slight effect on enhancing compressive strength. Where, these increase ranging from nil to 25%.
40
30
32.15
25.04
G 3 : RCA 70 %
34.52
36.22
27.56
29.48
37.78
31.70
20
10
0
RCA70 RCA70F5 RCA70F10 RCA70F15
Replacement ratio%
Fcu after 7days Fcu after 28days
40
30 23.70
G 4 : RCA 100 %
31.11
33.04
34.67
25.78
27.26
35.41
28.74
20
10
0
RCA100 RCA100F5 RCA100F10 RCA100F15
Replacement ratio%
Fcu after 7days Fcu after 28days
Figure 12 Compressive strength of 70%RCA Figure 13 Compressive strength of 100%RCA with different steel fiber content at 7and 28 days with different steel fiber content at 7and 28 days
4.2. Tensile strength
Tensile strength (Ft) is a considerable characteristic of hardened concrete. A total of 32 standard cylinder was poured with various RCA ratio and steel fiber content. The 28 days' tensile strength was taken as an average of 2 identical cylinders for each mix. The 28 days' indirect tensile strength for the studied mixes are shown in Table 6. Figure 14,15,16,17 and 18 show the effect of RCA replacement ratio and steel fiber content. Figure14 reveals that the results of tensile strength for mixes with natural aggregate decrease gradually by
13.53%,25.12% and 27.05% with increasing the Ra replacement ratio 30%,70%an d 100% respectively. Figure15 shows the influence of steel fiber content on tensile strength for mixes with NCA where the results shown that for 0.5%,1% and 1.5% steel fiber the tensile strength increased by 28.74%,40.34% and 59.42%. Figure16 displays the influence of steel fiber content on tensile strength for mixes with 70% NCA and 30%RCA where the results shown that for 0.5%,1% and 1.5% steel fiber the tensile strength increased by 22.35%,39.94% and
57.82%. Figure17 displays the influence of steel fiber content on tensile strength for mixes with 30% NCA and 70%RCA where the results shown that for 0.5%,1% and 1.5% steel fiber the tensile strength increased by 23.23%,49.03% and59%. Fig.18 displays the influence of steel fiber content on tensile strength for mixes with 0% NCA and 100%RCA where the results shown
5
4
3
2
4.14
3.58
3.10
3.02
G1: RCA0%(CONTROL MIX)
8
6
5.33
5.81
4.14
4
6.60
1
2
0
RCA00 RCA30 RCA70
Replacement ratio%
RCA100
0
RCA00 RCA00F5 RCA00F10 RCA00F15
Replacement ratio%
Figure 14 shows the effect of RCA ratios on Figure 15 Tensile strength of 0%RCA with tensile strength. different steel fiber content at 28 days http://www.iaeme.com/IJCIET/index.asp 1908 editor@iaeme.com

Sway of Steel Fiber and Recycled Aggregate Content on Mechanical Properties of Recycled
Aggregate Concrete that for 0.5%,1% and 1.5% steel fiber the tensile strength increased by 13.25%,31.79% and 47.68%.
4
3
2
1
6
5
0
3.58
G 2 : RCA 30 %
5.01
4.38
5.65
RCA30 RCA30F5 RCA30F10 RCA30F15
Replacement ratio%
Figure 16 Tensile strength of 3 0 %RCA with
G 3
:
RCA 70 %
6
5
4
3
2
1
0
3.10
3.82
4.62
4.93
RCA70 RCA70F5 RCA70F10 RCA70F15
Replacement ratio%
Figure 17
Tensile
strength of 7 0 %RCA with
G 4 : RCA 100 %
4
3
2
1
6
5
3.10
3.82
4.62
4.93
0
RCA70 RCA70F5 RCA70F10 RCA70F15
Replacement ratio%
Figure 18 Tensile strength of 100%RCA with different steel fiber content at 28 days
4.3. Flexural strength
The capability of beams to withstand failure in bending is defined as flexural strength. A total of 32 prisms was poured with various RCA ratio and steel fiber content with dimensions
100*100*500mm. The 28 days' flexure strength for the studied mixes are shown in Table 7.
Fig.19,20,21,22 and 23 show the effect of RCA replacement ratio and steel fiber content. In increasing the RCA replacement ratio, the flexure strength decreases by 16.32% at maximum
Figure 19 Flexure strength of 0%RCA with Figure 20 Flexure strength of 30%RCA with different steel fiber content at 28 days different steel fiber content at 28 days http://www.iaeme.com/IJCIET/index.asp 1909 editor@iaeme.com

Mohamed Husain, Khaled Fawzy and Khaled Fawzy Kotb percentage of replacement. However, the steel fiber has appositive influence on ductility and control cracks of concrete. This is evident in the above mentioned figures.
Table 6 Results of compressive strength after 7 and 28 days
Table 7 Results of tensile strength after 28 days http://www.iaeme.com/IJCIET/index.asp 1910 editor@iaeme.com

Sway of Steel Fiber and Recycled Aggregate Content on Mechanical Properties of Recycled
Aggregate Concrete
Table 8 Results of flexure strength after 28 days
By virtue of the results acquired from the laboratory tests. The results can be clarified as follows:

The compressive strength of old concrete which results in recycled aggregates whenever they are of high value. Whenever they have a positive reflection on the new concrete.

Increasing the ratio of replacing recycled aggregate with natural aggregates in concrete mix has a negative impact on mechanical properties. In the case of 100% RCA the compressive strength, tensile strength and flexure strength decreased by 14.97%,27.05% and 16.32% respectively.

During the casting and testing of samples, it was observed that the total replacement of NA with RA has a negative impact on workability and all mechanical properties of concrete.

The addition of fiber to recycled aggregate concrete improved the compressive strength, tensile strength and cracks. In addition to increase durability of concrete and failure load.

The best results were given at 70%RCA and 1% fiber content 1%. Where the results of the compressive strength, tensile strength and flexure strength were 36.22%,4.62% and 9.94% respectively and this achieving the desired strength.
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