ENGINEERING PROPERTIES OF SUSTAINABLE SELF- COMPACTING CONCRETE WITH CLAY BRICKS WASTE AGGREGATE

The present study covers the use of different percentages (25, 50, 75 and 100%) of clay bricks waste as replacement by volume of coarse natural aggregates to produce sustainable selfcompacted concrete (SCC). All mixes used containing 10% silica fume as a replacement by cement weight. The properties of SCC studied were, workability, fresh density, dry density, water absorption, compressive strength, splitting tensile strength, flexural strength, modules of elasticity and thermal conductivity. The results show that the flow ability, filing ability, and passing ability of self -compacted concrete through steel reinforcement are decrease with the increase of clay brick waste content. In addition, the segregation resistance decreases with the increase of clay brick waste content of SCC. The use of clay brick waste aggregate causes reduction in density, compressive strength, splitting tensile strength, flexural strength, modules of elasticity and thermal conductivity of SCC. The percentage reduction increases with the increase of clay bricks waste content in self-compacted concrete.


INTRODUCTION
Huge quantities of clay brick wastes are generating around the world due to the large using of these materials in buildings. The best solutions of sustainable waste management are the ability to Reduce, Reuse and Recycling of this waste to the maximum as possible (Rao, 2014;Hussain and Chandak, 2015). The use of clay bricks in large quantities is observed all over the world in latest years which leads to an increase in clay brick waste materials. Clay brick contains many venomous chemicals, and thus clay brick pollutes air, water and soil. Recently, a significant attention has been given to use the clay brick wastes in concrete industry. One of the perfect solution for disposing clay brick wastes is to reuse clay brick wastes to produce new type of concrete, which it is ecological and economic benefits (Alamgir and Ahsan, 2007). There is a significant possibility for the use of clay brick wastes as coarse aggregate in concrete preparation. The incorporation of clay brick wastes in concrete can significantly improves some self-compacted concrete properties, as clay bricks have low density, and high heat capability (Siddique et al., 2013).

Materials
Iraqi ordinary Portland cement Type I manufactured in the Najaf Governorate with trade mark of (kar) was used. It was stored in airtight plastic containers to avoid the exposure to atmospheric conditions. The results show that the cement used is corresponding with Iraqi standards No.5/1984(Iraqi Standard-No. 5, 1984. Natural sand with maximum aggregate size of 4.75mm was used. The physical properties and sieve analysis indicate that the fine aggregate used is within the requirements of the Iraqi Standard No.45/1984(Iraqi Standard-No. 45, 1984.
The grading and sulphate content of the natural crushed coarse aggregate satisfy the requirements of Iraqi Standard No.45/ 1984(Iraqi Standard-No. 45, 1984, with nominal maximum size of 12 mm. The water used for mixing and curing of self-compacted concrete was potable water. Also, admixture (superplasticizer) with a commercial mark of GLENIUM 54® was used. The recommended dosage by the manufacturer was in the range of 0.5-2.5 liters/100 kg of the cement. This type of admixture is free from chlorides and compatible with ASTM C494-04 type F (ASTM C494, 2007). Silica fume is used and satisfies the requirements of ASTM C1240-06 (ASTM C1240, 2006 limitation, its content is 10% as a parietal replacement of cement weight. Clay brick wastes were collected, crushed, washed and dried to have grading similar to that for natural coarse aggregate as shown in Fig. 1. The grading of clay Kufa Journal of Engineering, Vol. 9, No. 3, July 2018 225 brick waste aggregate used in this investigation is shown in Mixing of SCC was carried out in a rotary mixer with a capacity of 0.1m³. The mixing sequence was as following:  The fine aggregate was added to the mixer with 1/3 amount of water and mixed for 1.5 minutes.

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Wasan I. Khalil and Thaer A. Al-Daebal  The Portland cement and silica fume were added and then another 1/3 the amount of water was added and mixed for 3 minutes.
 Half the amount of coarse aggregate was added with the last 1/3 of water and 1/3 the dosage of superplasticizer and mixed for 1.5 minute then the mixture was left for 0.5 minute to rest.
 The remaining amount of coarse aggregate and Superplasticizer were added and mixed for 1.5 minutes. The mixture was then discharged, casted and cured.
This method was chosen according to the limitations of mixing taken by other researchers.

Preparation of Concrete Specimens
The steel molds were cleaned and lubricated to prevent adhesion with concrete after hardening.
SCC mixes do not require compacting, so the mixes were poured into the tight steel molds (cubes, cylinders and prisms) until these molds were fully filled without any compaction. The molds were covered with polyethylene sheet for about 24 hours.

Concrete Mixes
The details of SCC mixes prepared in this investigation are shown in Table 3.

Experimental Tests
Different tests were carried out in this investigation including:

Fresh Properties Tests for SCC
Fresh properties of SCC were tested according to the procedure of European Guidelines (EFNARE) (EFNARC, 2005) and ACI237-07 (ACI 237-07, 2007) for testing fresh SCC. Three properties were achieved by conducting five tests, which were flow ability, passing ability, and segregation resistance. These tests are:

Slump Flow Test
This test is used to estimate the horizontal free flow of SCC in the absence of obstructions and to assess the flow ability and deformability of SCC according to (EFNARE) (EFNARC, 2005).

V-Funnel Test
The V-Funnel test is used to measure the filling ability of SCC and can be used to judge segregation resistance according to (EFNARE) (EFNARC, 2005).

L-Box Test
Kufa Journal of Engineering, Vol. 9, No. 3, July 2018 227 This test is used to estimate the filling and passing ability of SCC to flow through tight opening includes spaces between reinforcing bars and other obstructions without blocking or segregation according to (EFNARE) (EFNARC, 2005).

Column Segregation Resistance Test
It is used to estimate the resistance of self-compacting concrete to segregation according to ACI237-07 (ACI 237-07, 2007).

Fresh Density
The fresh density of self-compacted concrete was computed directly after mixing according to ASTM C 138M-01 (ASTM C138, 2015).

Hardened Concrete Tests for SCC
In hardened phase, the tests carried out for hardened SCC were:

Compressive Strength Test
This test was carried out on concrete cube specimens of 100 mm according to BS 1881: part116 (B.S.1881(B.S. : Part 116, 1989.

Splitting Tensile Strength Test
The splitting tensile strength test was carried out on cylindrical specimens of 100 x 200 mm according to ASTM C496-07 (ASTM C496, 2015).

Modulus of Rupture Test (Flexural Strength)
The modulus of rupture test was carried out on concrete prismatic specimens (100 x 100 x 400 mm) to estimate the modulus of rupture under two point loads according to ASTM C78-02 (ASTM C78, 2015).

Oven Dry Density and Absorption Water Tests
Oven dry density and absorption of concrete were determined at 28 day age according to ASTM C 642 -97 (ASTM. C642, 2015).

Ultrasonic Pulse Velocity Test
This test was determined at 28 day age according to ASTM C597 (ASTM C597, 2002).

Static Modulus of Elasticity
This test was determine at 28 day age according to ASTM C469 (ASTM C469, 2002).

Thermal Conductivity
This test was determine at 28 day age according to ASTM C-1113 (ASTM C-1113, 2013).

Selection of Mix Proportions
The mix proportions used was 1:1.72:1.97 (cement sand: gravel), with cement content of 450 kg/m³, and w/c ratio of 0.38. This self-compacting concrete mix was designed according to EFNARC (EFNARC, 2005), to obtain concrete with minimum compressive strength of 40 MPa at 28 day.
Several trial mixes were carried out to select the optimum dosage of high range water reducing admixture (HRWRA) that satisfies the standard limitations for workability of SCC. According to the manufacturer, the recommended dosage of HRWRA (GLENIUM 54®) is between 0.5 and 2.5 liters per 100 kg of cement (cementitious material). The experimental results in this study indicate that the optimum dosage of HRWRA is 2.2 liters per 100 kg of cement.
It can be seen that HRWRA leads to a significant improvement in compressive strength and causes a decrease in water cement ratio compared with the reference mix. This is attributed to the action mode of the superplasticizer, that when it is added to cement water system, the polar Kufa Journal of Engineering, Vol. 9, No. 3, July 2018 229 chain is adsorbed on the surface of cement particles. That gives strong negative charge around the grains lowering the inter particles attraction by an electrostatic mechanism and reduces the amount of water required to attain equal workability (Cement Admixtures Association, 2012).
Finally, 10% silica fume was used as a replacement to cement weight. The results indicate that the use of silica fume improves the flow ability, filing ability, and passing ability of selfcompacted concrete through steel reinforcement.
The limits of EFNARC (EFNARC, 2005) and ACI237-07 (ACI 237-07, 2007) of SCC are given in Table 4, also the properties of self-compacted concrete mixes containing different dosages of superplasticizer and the properties of reference self-compacted concrete mix containing silica fume (10%) are given in Table 5. The relationship between the different dosages of HRWRA and compressive strength of SCC is shown in Fig. 2.

Workability
The test results in Table 6 illustrate that the slump flow decreases, the filling time increases, and the speed of passing of fresh self-compacted concrete thought reinforcement bars decreases with the inclusion of clay brick waste aggregate.
Kufa Journal of Engineering, Vol. 9, No. 3, July 2018 231 This is because the water absorption of clay brick wastes is high compared with the natural coarse aggregate. On the other hand, the segregation resistance (S.R) of fresh concrete is decreased with increasing the percentage of plastic wastes as a replacement by volume of coarse natural aggregate.

Fresh Density
Generally, the results in Table 6 show a reduction in the fresh density with the increase of clay bricks waste content compared with the reference mix (without clay brick wastes). This is due to the low density of clay brick wastes 1611 kg/m3 compared with the density of coarse natural aggregate 1753 kg/m 3 . The percentage reduction increases with the increase of clay brick wastes content in concrete. This is due to the shape of clay brick aggregate that leads to increasing the continuous path between pores and increases porosity. Also, the low density of clay brick waste leads to unsuitable compaction then more pores is formed.

Oven Dry Density and Water Absorption
The water absorption for all self-compacted concrete specimens with clay bricks waste is ranged from 1.69% to 2.29% that is less than 10%. This displays the good quality of all SCC mixes prepared in this investigation (Neville, 2011).

Compressive, Splitting Tensile, Flexural Strengths, Ultrasonic Pulse Velocity and Static Modulus of Elasticity
The effect of different percentages of clay brick wastes as a replacement by volume of coarse aggregate (25%, 50%, 75%, and 100%) on compressive, splitting tensile, flexural strengths, ultrasonic pulse velocity (UPV) of SCC at 28 day age are shown in This reduction in the compressive strength or UPV, splitting tensile and flexural strengths are attributed to the reduction in adhesive strength between the surface of particles of clay brick waste and the cement paste. Also, it is due to the mismatch of particles size and shape between natural and partials of clay brick waste aggregate. The smooth surface of the clay brick waste particles may cause a weak bonding strength between clay brick waste waste and the cement paste (Kinda et al., 2010).
In addition, the natural aggregate is stronger than clay brick aggregate, and as the most strength of concrete is from the strength of aggregate because approximately three quarters of the volume of concrete is occupied by aggregate (Zongjin, 2011).
The relationship between clay brick waste content and the compressive strength of SCC is shown in Fig. 3.

Static Modulus of Elasticity
The effect of different percentages of clay brick wastes as a replacement by volume of coarse aggregate (25%, 50%, 75%, and 100%) on static modulus of elasticity of SCC at 28 day age are shown in Table 6. The percentages reduction in the static modulus of elasticity of SCC with 25%, 50%, 75% and 100% are 17.26%, 31.15%, 39.22%, and 49.66% respectively relative to SCC specimens without clay brick waste aggregate.
The reduction in modulus of elasticity can be attributed to the lower modulus of elasticity of clay brick waste particles compared with natural coarse aggregate. Also, the low bond between the cement paste (matrix) and clay brick waste aggregate can also contribute to this drop (Saikia and De. Brito, 2013). According to Jones and Facaroau (cited by (Rahmani et al., 2013)) the modulus of elasticity is affected by type of aggregate, since the deformation produced in the Kufa Journal of Engineering, Vol. 9, No. 3, July 2018 233 concrete specimens is partially related to the elastic deformation of the aggregate. Therefore, the partial replacement of natural aggregate by clay brick wastes aggregate implies that the modulus will be gradually decrease since the clay brick has less static modulus than the natural coarse aggregate and will deform at lesser stress compared with natural aggregate.

Thermal Conductivity
The effect of different percentages of clay brick wastes as a replacement by volume of coarse aggregate (25%, 50%, 75%, and 100%) on thermal conductivity of SCC at 28 day age are shown in Table 6.
It can be observed a considerable reduction in thermal conductivity with the increase in clay brick waste aggregate content. This is due to the formation of huge amount of cavities in the structure of concrete containing clay bricks waste aggregate. Porosity is one of the factors affecting the thermal conductivity of concrete and enclosed pores reduce the conductivity due to the low thermal conductivity of air (Semiha et al., 2013).

Fig. 3. Relationship between Clay Bricks Wastes Content and the Compressive Strength
of Self-Compacted Concrete. increases with the increase of clay brick wastes content in SCC.
5-The use of clay brick waste in different percentages (25%.50%,75%,and 100%) as a replacement by volume of natural coarse aggregate in SCC mixes significantly reduces the fresh, and dry density compared with the reference SCC mix (without clay bricks waste).
The percentage decrease increases with the increase of clay bricks waste content in concrete.
6-SCC specimens containing different content of clay brick waste show an increase in water absorption compared with the reference SCC concrete (without Clay bricks waste).