INTERNATIONAL JOURNAL OF CIVIL AND STRUCTURAL ENGINEERING Volume 3, No 1, 2012

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1 INTERNATIONAL JOURNAL OF CIVIL AND STRUCTURAL ENGINEERING Volume 3, No 1, 2012 Copyright by the authors - Licensee IPA- Under Creative Commons license 3.0 Research article ISSN Performance of concrete containing crushed waste concrete exposed to different fire temperatures Walid Safwat Fahmy 1, Erfan Abdel-Latif Heneidy 2, Esraa Emam Ali 3, Ibrahim Saad Agwa 4 1- Faculty of petroleum and Mining Engineering, Suez Canal University, Suez, Egypt, 2- Civil Engineering Dept., Faculty of Engineering,Suez Canal University, Ismailia, Egypt, 3- Building Materials and Quality Control Insitute, Housing and Building National Research Center-Dokki-Cairo, Egypt 4- Civil Structures Dept., Faculty of Industrial Education, Suez Canal Univ., Suez, Egypt doi: /ijcser ABSTRACT Recycled aggregate obtained from the construction and demolition waste has currently received increasing attention, due to its potential to be used in environmentally friendly concrete structures. Further, the deficiency of natural aggregates, shortage of dumping sites, increase in transport cost and environmental pollution lead to use of recycled aggregate as a substitute material in the production of concrete in many countries. This experimental study demonstrates the properties of concrete containing crushed waste concrete exposed to different fire temperatures. In the experimental work, the fresh concrete properties (slump test) and the hardened concrete properties, (compressive strength, splitting tensile strength, flexural strength and modulus of elasticity) were carried out. A total of thirty concrete mixes with different cement contents (300, 350, and 400 Kg/m 3 ) at w/c ratio (0.5) were made and the percentage of replacement of natural coarse aggregate by fired recycled coarse aggregate at fire temperatures (300,600 and 800 C) for fire duration (2) hours was (0, 25, 50 and 100%). In the process of mixing, equal consistence among all concrete mixes was achieved. The obtained results indicate that the recycled coarse aggregate subjected to fire can successfully be used for making structural concrete. Keywords: Crushed waste concrete, Fired recycled coarse aggregate, Fire temperature, Compressive strength, Tensile strength, Flexural strength and Modulus of elasticity. 1. Introduction The use of recycled aggregate in replacing the normal coarse aggregates in concrete construction has become popular among researchers (Abdul Rahman et al., 2009), recycled concrete aggregate normally has higher water absorption and lower specific gravity.the density of recycled aggregate is lower than density of normal aggregate as the porosity of recycled aggregate is much higher than those of natural aggregate (Yong and Teo., 2009). The workability (slump test) of RAC is lower than NAC because the rate absorption of RA is higher than NA (Abdul Rahman et al., 2009). Air content of recycled concrete is higher than in conventional concrete when aggregates are used in a dry condition (Juan. and Gutiérrez, 2004), and (Etxeberria et al, 2007). Conducted an investigation study, recycled coarse aggregates obtained by crushed concrete were used for concrete production. Four different recycled aggregate concretes were produced; made with 0%, 25%, 50% and 100% of recycled coarse aggregates, respectively. The mix proportions of the four concretes were designed in order to achieve the same compressive strengths. Concrete made with 100% of Received on May, 2012 Published on July

2 recycled coarse aggregates has 20 25% less compressive strength than conventional concrete at 28days (Etxeberria et al., 2007). According to (Juan and Gutiérrez., 2004), the compressive strength of recycled concrete is lower than compressive strength of a control concrete with the same dosage (equal water/cement ratio and cement content). Recycled concretes with a percentage of recycled coarse aggregate lower than 50% shows decreased in compressive strength with range 5-10%, while for concretes with 100% recycled aggregates, the decrease ranged from 10-15%. The elastic modulus of RAC is lower than that of the normal concrete. It decreases as the RCA content increases. For a RCA replacement percentage equals 100%, the elastic modulus is reduced by 45% (Xiaoa et al., 2005). Yuzer et al., In previous studies, it has been mentioned, especially for concretes produced with siliceous aggregates, that if the residual color is pink or red, it indicates that the temperature is raised up to C; if it is gray; it shows that temperature is raised up to C. When the temperature reaches 600 and 800 C, concrete loses 50% and 80% of its strength, respectively, which gives an idea about which temperature the concrete was exposed to by determining its color. 2. Experimental work 2.1 Materials Cement Ordinary Portland cement was used. Mechanical properties, physical properties of the used cement are given in Tables (1). Testing of cement was carried out according to Egyptian Standard Specification (ESS , 2007). Table 1: Mechanical and physical properties of cement Property Results Specifications Limits* Compressive Strength of Standard Mortar (MPa) 28 days 2 days 21.4 Not less than Not less than Not more than 62.5 Soundness (La Chatelier) (mm) 1 Not more than 10 Setting Time (min) *Limits of (ESS , 2007) Fine aggregate Initial 135 Not less than 60 Final Natural sand composed of siliceous materials was used as Fine Aggregate (FA) in this study. Testing of sand was carried out according to the (ESS 1109, 2002). Table (2) shows the physical properties of the sand. Table 2: Physical properties of fine aggregate Property Results Limits* Specific Weight Bulk Density (t/m 3 ) Clay and Fine Dust Content (% By Volume) 1.4 Not more Than 4 *Limits of (ESS 1109.,2002) 10

3 2.1.3 Coarse aggregate Both Natural Coarse Aggregate (NCA) and Fired Recycled Coarse Aggregate (FRCA) were used in this study Natural coarse aggregate Natural crushed stone (dolomite) was used in this study. Testing of natural coarse aggregate (NCA) was carried out according to the (ESS 1109, 2002) Mechanical and physical properties of the NCA comply with both the (ESS 1109, 2002) and the Egyptian Code (ECCS203, 2007) The physical and mechanical properties of the NCA are shown in Tables (3). Table 3: Physical and mechanical properties of natural coarse aggregate Property Results Limits Specific Weight Bulk Density (t/m 3 ) Water Absorption % 2.05 Not more than 2.5** Clay and Fine Dust Content % 2.4 Not more than 4* Flakiness Index % 36.8 Not more than 40* Elongation Index % 9.6 Not more than 25** Abrasion Index % 17.8 Not more than 30* Impact Value % Not more than 45* *Limits of (ESS 1109, 2002) **Limits of (ECCS203, 2007) Fired recycled coarse aggregate The fired recycled coarse aggregate used in this study were produced by crushing the fired concrete. Jaw crusher type (BB300) was used to gash the fined elements into wise recycled aggregate with fraction size 10 mm. Testing of FRCA was carried out according to the (ESS 1109, 2002), and the Egyptian Code (ECCS203, 2007). The physical and mechanical properties of the FRCA are shown in Table (4). Table 4: Physical and mechanical properties of fired recycled coarse aggregate Property FRCA 300 C- 2 hrs Results FRCA 600 C- 2 hrs FRCA 800 C- 2 hrs Limits Specific Weight Bulk Density (t/m 3 ) Water Absorption % Not More than 2.5** Clay and Fine Dust Content % Not More than 4* *Limits of (ESS 1109, 2002) **Limits of (ECCS203, 2007) 11

4 2.1.6 Mixing water Drinking water was used for mixing Plasticizer In this study, In order to obtain same workability without increased water, plasticizer admixture ADDICRETE BV was used. ADDICRETE BV is a plasticizer and flowing concrete admixture (Complies with ASTM C type A, DIN 10045, BS 5075PART 1), it has the following properties, base material was lingo sulphonates, density was 1.18± 0.01/1 at 25 C and it was combatable with types of Portland cement. 2.2 Preparation of fired recycled coarse aggregate Obtaining the fired recycled coarse aggregate is based on three stages as shown in Figure (1). Stages (1) Concrete Waste collection Collected from different locations in Cairo, Stages (2) The setup of fire furnace and Stages (3) Crushing of concrete.the crusher used in this study was jaw crusher (type BB300). 2.3 Concrete mixes Figure 1: Preparation of fired recycled coarse aggregate The concrete mixes were prepared in the laboratory of Housing and Building National Research Center. A total of thirty concrete mixtures were made with different cement contents (300,350, and 400 kg/m 3 ) at w/c = (0.5), the plasticizer dosage varied from 0.6% to 3.5% of cement content to achieve the required level of workability defined by a slump value of 10± 2cm. The percentage of replacement of natural coarse aggregate by fired recycled coarse aggregate at fire temperatures (300,600 and 800 C) for fire duration (2) hours was (0%, 25%, 50% and 100%). Control mixes made with the natural aggregate, and the other concrete mixes were made using a fired recycled aggregates, the ratio of fine to coarse aggregate was about 1:2.Composition of designed mixtures has been shown in Table (5). 12

5 Table 5: Concrete mixtures proportions at fire duration (2) hours for fire temperatures (300,600 and 800 C) Mix NO Designation W P% 300 C 600 C 800 C C FA NCA Control M1 (M-0% -300 ) G1 (300,600 M2 (M-25%-300 ) and M3 (M-50%-300 ) C) 9 mixes M4 (M-100%-300 ) Control M5 (M-0%-350 ) G2 (300,600 M6 (M-25%-350 ) and M7 (M-50%-350 ) C) 9 mixes M8 (M-100%-350 ) Control M9 (M-0% ) G3 (300,600 and 800 C) 9 mixes Where W= Water (Litre/m 3 ) FRC A M10 (M-25%-400 ) M11 (M-50%-400 ) M12 (M-100%- 400) P%; Plasticizer percentage of cement content C (kg/m 3 ) = Cement content FA (kg/m 3 ) = Fine aggregates (sand) NCA (kg/m 3 ) = Natural coarse aggregate FRCA (kg/m 3 ) = Fired Recycled coarse aggregate 3. Concrete tests All the concrete mixes were mixed in the laboratory of Housing and Building National Research Center (HBRC). The slump test was conducted on fresh concrete to determine the slump value. For each concrete mix, six 150*150*150 mm cubes were casted to determine the compressive strength at 7 and 28 days. Three 150mm * 300mm cylinders were casted for the determination of indirect tensile strength at 28 days. Three beams of dimensions 100 * 100 * 500 mm were casted for the determination of flexural strength at 28 days. Three 150mm * 300mm cylinders were casted for the determination of modulus of elasticity at 28 days. After casting, all the casted specimens were covered by plastic sheets and water saturated burlap and left in the laboratory at 20 ± 3 c for 24 h. the specimens were then demoulded and transferred to a saturated water curing tank at 25 c until the age of testing. 13

6 4. Results and discussion 4.1 Properties of fired recycled aggregate Visual observation reveals that the surface texture of fired recycled coarse aggregate are porous and rough due to the old cement paste remains adhered to the fired recycled aggregate after the recycling process. This may demands more dosage of plasticizer requirement for achieving the required workability. The physical properties of fired recycled aggregate are presented in Table (4). 4.2 Water absorption The water absorption for concrete made of fired recycled coarse aggregates is much higher than that for concrete, which made of the natural coarse aggregate due to the large amounts of old mortar and cement paste attached to fired recycled coarse aggregate and dehydration. The water absorption of fired recycled coarse aggregate is ranged from 4.9% to 9% for different fire temperatures. 4.3 Specific gravity Due to the large amount of old mortar and cement paste adhering to fired recycled coarse aggregate, their specific gravity will be 10% to 20% lower than that of the natural coarse aggregate. The specific gravity of fired recycled coarse aggregate is ranged from 2.05 to 2.35 for different fire temperature. 4.4 Bulk density The reduction of the bulk density of fired recycled coarse aggregate ranged from 2.55% to 7% for different fire temperatures. As the old cement mortar adhered to aggregate in fired recycled coarse aggregate is light and dehydration, it is obvious that the bulk density of fired recycled coarse aggregates are lower than that of natural coarse aggregate. 4.5 Clay and fine dust content The clay and fine dust content of fired recycled coarse aggregates is much higher than that of the natural coarse aggregates due to destruction of the bond between the cement paste and the aggregate. The clay and fine dust content of fired recycled coarse aggregates is ranged from 5% to 14% for different fire temperatures. 4.6 Fresh concrete properties The dosage of superplasticizer added to different concrete mixes to maintain a constant slump of 10± 2 cm was shown Figure (2). Also Figure (2) shows the comparison between concrete groups (300 C-2hrs, 600 C-2hrs, and 800 C-2hrs), it can be noticed that the dosage of plasticizer should be increased significantly by increasing the percentage of replacement ratio of fired recycled coarse aggregate. Due to the large amounts of old mortar and cement paste attached to fired recycled coarse aggregate and dehydration. 14

7 plasticiczer dose (% of cement content) % RCA 25% RCA 50% RCA 100% RCA 300 C.C 350 C.C 400 C.C 300 C.C 350 C.C 400 C.C 300 C.C 350 C.C 400 C.C 300Co at 2 h-rs 600Co at 2 h-rs 800Co at 2 h-rs Concrete mixes Figure 2: Plasticizer dosage for concrete mixes 4.7 Hardened concrete properties Compressive strength The compressive strength results at 7 and 28 days of concrete mixtures subjected to fire temperature 300 C for fire duration 2hours were presented in Table (6). It was observed that the compressive strength of concrete mixtures with percentage of replacement ratios of FRCA 0%, 25%,50 % and 100% were increased by (26%,33%,20% and 32 %), (28%,38%,27%and 39%) and (34%, 49%, 43 and 38%) for cement contents 300,350 and 400 kg/m 3 from 7 to 28 days respectively. Figure (3-a) it can be noticed that at replacement ratio 25% FRCA, there are differences in the compressive strength of 2% and 1% at cement contents of 300 and 350kg/m 3 respectively. The compressive strength at cement content of 400kg/m 3 decreased by 1% comparing with control mixtures at 28 days. This result is confirmed by (Etxeberria et al., 2007),. Who found that the results up to 25% RCA has no major effect on compressive strength. (Notice that the RCA used in the previous studies was not exposed to fire). While at replacement ratios (50% and 100%) FRCA, there is a reduction in the compressive strength by (11% and 19%), (12% and 20%) and (13% and 23%) for cement contents 300,350 and 400kg/m 3 respectively, comparing with control mixtures at 28 days. This may be attributed to the weak bond between the fresh mortar and the old mortar adhering to the fired recycled coarse aggregates in addition to the low resistance of the fired recycled coarse aggregates to the mechanical action compared with the natural aggregates. The results are in agreement with (Juan. and Gutiérrez, 2004), who found that up to 50% RCA decrease in the compressive strength by 5% to 10%, while at full replacement ratio of RCA, The results in agreement with ( Hansen., 1992), who stated in his literature the compressive strength decreased by 20%. (Notice that the RCA used in the previous studies was not exposed to fire). The compressive strength results at 7 and 28 days of concrete mixtures subjected to fire temperature 600 C for fire duration 2hours were presented in Table (6). 15

8 It was observed that the compressive strength of concrete mixtures with percentage of replacement ratios of FRCA 0%, 25%,50 % and 100% were increased by (26%,39%,25% and 33 %), (28%,43%,26%and 20%) and (34%, 57%, 36 and 27%) for cement contents 300,350 and 400 kg/m 3 from 7 to 28 days respectively. It can be noticed from Figure (3-b) that at replacement of natural coarse aggregates with 25% FRCA, there is a slight decrease in the compressive strength of concrete by 3% at cement contents (300 and 350 kg/m 3 ), while the compressive strength decreased by 4% at cement content 400 kg/m 3. At replacement ratios (50% and 100%) FRCA, there is a reduction in the compressive strength by (18% and 24%), (19% and 30%) and (18% and 28%) for cement contents 300,350 and 400 kg/m 3 respectively, comparing with control mixtures. Also the compressive strength results at 7 and 28 days of concrete mixtures subjected to fire temperature 800 C for fire duration 2hours were presented in Table (6).It was observed that the compressive strength of concrete mixtures with percentage of replacement of FRCA 0%, 25%,50 % and 100% were increased by (26%,26%,25% and 18 %), (28%,23%,24%and 20%) and (34%, 34%, 24 and 17%) for cement contents 300,350 and 400 kg/m 3 from 7 to 28 days respectively. Figure (3-c) it can be noticed that as fire temperature and fire duration increased there is a significant disintegration of the calcium silicate hydrate as well as partial disintegration occurs in the aggregate. Replacement of natural coarse aggregates with 25% fired recycled coarse aggregates showed different results depending on cement content of mixtures. The decreased of compressive strength by 16% at cement content of 300 kg/m 3, while the compressive strength decreased by 15% for cement contents (350 and 400 kg/m 3 ), comparing with control concrete. On the other hand, at replacement ratios (50% and 100%) FRCA, there is a reduction in the compressive strength by (26% and 48%), (29% and 51%) and (28% and 52%) for cement contents 300,350 and 400 kg/m 3 respectively, comparing with control concrete. Where Table 6: Compressive strength of concrete mixtures at fire temperatures (300,600 and 800 C) for fire duration (2) hours Group G1 G2 G3 Designation Compressive strength at 7 days (N/mm 2 ) Compressive strength at 28 days (N/mm 2 ) 300 C 600 C 800 C 300 C 600 C 800 C M1(M-0%-300) M2(M-25%-300) M3(M-50%-300) M4(M-100%-300) M5(M-0%-350) M6(M-25%-350) M7(M-50%-350) M8(M-100%-350) M9(M-0%-400) M10(M-25%-400) M11(M-50%-400) M12(M-100%-400) MG (M-% C) Where M, refers to mix % refers to fire recycled coarse aggregates C, refers to cement content (kg/m 3 ) 16

9 G, refers to group number (a) (b) (c) a- Temperature 300 C b- Temperature 600 C c- Temperature 800 C Figure 3: Relationship between compressive strength and percentage of replacement of (FRCA) for different cement contents at fire duration 2 hrs at 28 days Tensile strength It can be noticed from Figure (4-a) that at replacement ratio 25% FRCA, has no effect on tensile strength, while at replacement ratios (50% and 100%) FRCA, there is a reduction in the tensile strength by (12% and 18%), (14% and 19%) and (10% and 20%) for cement contents 300,350 and 400 kg/m 3 respectively, comparing with control mixtures. This may be attributed to the fracture surfaces of tensile specimens indicates that the failure occurred through the fired recycled coarse aggregate in addition to the failure occurred through the interfaces in case of fired recycled coarse aggregate. This results is confirmed by (Rao et al, 2007), who found that the full replacement of RCA decrease the tensile strength by (15 to 20%). (Notice that the RCA used in the previous studies was not exposed to fire).it can be noticed from Figure (4-b) that at replacement ratio 25% FRCA, there is a decrease in the tensile strength by 7%,5% and 5% for cement contents 300,350 and 400kg/m 3 respectively, comparing with control mixtures. While at replacement ratios (50% and 100%) FRCA, there is a reduction in the tensile strength by (17% and 27%), (15% and 25%) and (15% and 26%) at cement contents 300,350 and 400 kg/m 3 respectively, comparing with control mixtures. This agrees with (Nelson and Shing., 2004), who found that the full replacement of RCA at w/c ratio =0.43 decrease the tensile strength by 22%. (Notice that the RCA used in the previous studies was not exposed to fire).it can be noticed from Figure (4-c) that replacement ratio 25% FRCA, there is a decrease in the tensile strength by 12%, 12% and 13% for cement 17

10 contents 300,350 and 400kg/m 3 respectively, comparing with control mixtures, While at replacement ratios (50% and 100%) FRCA, there is a reduction in the tensile strength by (18% and 40%), (19% and 39%) and (21% and 42%) for cement contents 300,350 and 400 kg/m 3 respectively, comparing with control mixtures. a- Temperature 300 C b- Temperature 600 C c- Temperature 800 C Figure 4: Relationship between Tensile strength and percentage of replacement of (FRCA) for Different cement contents at fire duration 2 hrs at 28 days Flexural strength It can be noticed from Figure (5-a) that at replacement ratio 25% FRCA, has no effect on flexural strength, while at replacement ratios (50% and 100%) FRCA, there is a reduction in the flexural strength by (14% and 22%), (16% and 24%) and (16% and 26%) for cement contents 300,350 and 400kg/m 3 respectively, comparing with control mixtures. This agrees with (Hansen., 1992), who stated in his literature that the flexural strength of RCA produced with both fine and coarse aggregate to be reduced by 26%. (Notice that the RCA used in the previous studies was not exposed to fire). It can be noticed from Figure (5-b) that at replacement ratio 25% FRCA, there is a reduction in the flexural strength by 5%,4% and 9% for cement contents 300,350 and 400kg/m 3 respectively, comparing to control mixtures, while at replacement ratios (50% and 100%) FRCA, there is a reduction in the flexural strength by (18% and 30%), (20% and 31%) and (18% and 30%) for cement contents 300,350 and 400 kg/m 3 respectively, comparing with control mixtures. It can be noticed from Figure (5-c) that at replacement ratio 25% FRCA, there is a reduction in the flexural strength by 13%, 12% and 13% for cement contents 300,350 and 400kg/m 3 respectively, comparing with control mixtures, while at replacement ratios (50% and 100%) FRCA, there is a reduction in the flexural strength by (25% and 45%), (26% and 47%) and (28% and 47%) for cement contents 300,350 and 400 kg/m 3 respectively, comparing with control mixtures Modulus of elasticity It can be noticed from Figure (6-a) that at replacement ratio 25% FRCA, there is a reduction in the modulus of elasticity by 12%,10%and 13% for cement contents 300,350 and 400kg/m 3 18

11 respectively, comparing with control mixtures, while at replacement ratios (50% and 100%) FRCA, there is a reduction in the modulus of elasticity by (20% and 33%), (17% and 36%) and (18% and 33%) for cement contents 300,350 and 400kg/m 3 respectively, comparing with control mixtures. 19

12 a- Temperature 300 C b- Temperature 600 C c- Temperature 800 C Figure 5: Relationship between flexural strength and percentage of replacement of (RCA) for different cement contents at fire duration 2 hrs at 28 days This may be attributed the presence of more micro cracks and weaker interfaces in recycled aggregate concretes. In addition to large amount of old, mortar which is attached to original aggregate particles in recycled aggregates. The results in agreement with (Juan. and Gutiérrez, 2004), who found elasticity modulus is one of the most affected properties of recycled concretes, even with low percentages of RCA 20%, 50% and 100% have given average values of modulus of elasticity 10%, 20% and 40% lower than the corresponding natural aggregate concrete. (Notice that the RCA used in the previous studies was not exposed to fire). It can be noticed from Figure (6-b) that at replacement ratio 25%FRCA, there is a reduction in the modulus of elasticity by 16%,15% and 17% for cement contents 300,350and 400kg/m 3 respectively, comparing with control mixtures, while at replacement ratios (50% and 100%) FRCA, there is a reduction in modulus of elasticity by (24% and 45%), (25% and 46%) and (22% and 46%) at cement contents 300,350 and 400kg/m 3 respectively, comparing with control mixtures. This result is confirmed (Xiaoa et al., 2005), who found the elastic modulus of RCA is lower than that of the normal concrete. It decreases as the RCA content increases. For a RCA replacement percentage equals 100%, the elastic modulus is reduced by 45%. (Notice that the RCA used in the previous studies was not exposed to fire). It can be noticed from Figure (6-c) that at replacement ratio 25% FRCA, there is a reduction in the modulus of elasticity by 19%, 21%and 22% for cement contents 300,350 and 400kg/m 3 respectively, comparing with control mixtures, while at replacement ratios (50% and 100%) 20

13 FRCA, there is a reduction in the modulus of elasticity by (29% and 58%), (31% and 59%) and (30% and 61%) for cement contents 300,350 and 400 kg/m 3 respectively, comparing with control mixtures. a- Temperature 300 C b- Temperature 600 C c- Temperature 800 C Figure 6: Relationship between modulus of elasticity and percentage of replacement of (RCA) for different cement contents at fire duration 2 hrs at 28 days 5. Conclusions 1. To achieve the required level of workability defined by a slump value of 10± 2 cm, the dosage of plasticizer should be increased significantly by increasing the percentage of replacement ratio of FRCA in the concrete mixtures Replacement of natural aggregate up to 25% FRCA at fire temperature up to 600 C for different fire durations has a minor effect on compressive, tensile and flexural strengths. 3. As a result of changing fire temperatures from 300 to 800 o C for 2hours fire duration, the compressive strength of the concrete decreases from 11 to 21% and from 19 to 52% for 50% and 100% FRCA respectively. 4. As a result of changing fire temperatures from 300 to 800 o C for 2hours fire duration, the tensile strength of the concrete decreases from 10 to 21% and from 18 to 42% for 50% and 100% FRCA respectively, comparing with control mixtures. 5. As a result of changing fire temperatures from 300 to 800 o C for 2hours fire duration, the flexural strength of the concrete decreases from 13 to 28% and from 22 to 47 % for 50% and 100% FRCA respectively, comparing with control mixtures. 6. As a result of changing fire temperatures from 300 to 800 o C for 2hours fire duration, the modulus of elasticity of the concrete decreases from 17 to 31% and from 33 to 61% for 50% and 100% FRCA respectively, comparing with control mixtures. 7. Fired recycled coarse aggregates at 800 o C fire temperature for 2hours fire duration can be used for non-structural applications such as (concrete blocks, pavement, concrete kerb, interlock and backfill materials, etc.). 21

14 6. References 1. Abdul Rahman, I.; Hamdam,.H. and Zaidi, A. M., (2009, a ), Assessment of recycled aggregate concrete, Journal of modern applied science, 3, pp Yong, P.C. and Teo, D.C.L., (2009, b ), Utilization of recycled aggregate as coarse aggregate in concrete, Journal of civil engineering, pp Juan, M.S. and Gutiérrez, P.A., (2004, a ), Influence of recycled concrete aggregate quality on concrete properties. International RILEM conferences on the use of recycled materials in building and structures, Barcelona, Spain, pp 9-11 November. 4. Etxeberria, M.E.; Vázquez, A.; Marí,.A. and Barra,.M., (2007, a ), Influence of amount of recycled coarse aggregates and production process on properties of recycled aggregate concrete, Journal of cement and concrete research, 37, pp Xiaoa, J.; Lia, J. and Zhang,.C., (2005), Mechanical Properties of Recycled Aggregate Concrete under Uniaxial Loading, Journal of Cement and Concrete Research, 35, pp Yuzer, N.; Akoz,.F. and Ozturk,.L., (2004, b ), Compressive strength color change relation in mortars at high temperature, Journal of cement and concrete research, 34, pp ESS / (2007, b ), Egyptian standard specification -Cement-physical and mechanical tests. 8. ESS 1109/ (2002), Egyptian standard specification -Aggregates for concrete. 9. Egyptian Code of Practice for Design and Construction of Concrete Structures ECCS ( , c ). 10. Hansen,T. C., (1992), Recycling of demolished concrete and masonry. Report of Technical committee 37-DRC demolition and reuse of concrete, Hartnolls Ltd,Bodmin, Great Britain. 11. Rao,.A; Jha,.K. N. and Misra,.S., (2007, d ), Use of aggregates from recycled construction and demolition waste in concrete. Journal of resources conservation and recycling, 50, pp Nelson and NGO, S. C., (2004, c ), High-strength structural concrete with recycled aggregates. Research project, Faculty of engineering and surveying, University of southern Queensland. 22