Concrete wastes are generally delivered to the landfill sites for disposal. Due to increasing charges of landfill and scarcity of Natural Coarse Aggregate (NCA), recycled concrete aggregate (RCA) derived from concrete wastes is growing interest in construction industry. In the present study, RCA was used as partial and full replacements of NCA to produce durable Self-Compacting Concrete (SCC). Different SCC mixes were produced with RCA substituting 0%, 25%, 50%, 75%, and 100% NCA by weight, 20% MP and 3% admixture. The water to powder (W/P) ratio are variable after adding water absorption to concrete mixes. The effects of RCA on the key fresh properties such as filling ability, passing ability, and segregation resistance of SCC were investigated and the effects of RCA on hardened concrete such as cube and splitting strength , abrasion resistance , Cantabro test and RCPT test to evaluate durability. The test results revealed that the filling ability and passing ability of SCC were improved for all mixes. All mixes of SCC also possessed adequate segregation resistance. In addition, strong correlations were observed for passing ability, and segregation resistance. The test result of hardened concrete revealed that mixes up to 50%RCA gives normal strength and accepted durability. From the overall test results it could be concluded that RCA can be used to produce SCC substituting up to 50% NCA without affecting the key properties of fresh concrete, give normal strength and accepted durability.

Marble powder is available in various parts of the world abundantly as there is a great demand of marble stones. The particle size of this material is marginally courser compared to cement and fly ash. In the present study, results of an experimental study to show the possibility of use of marble powder in self-compacting concrete (SCC) , it clearly shows that Marble powder can be used in SCC. Different SCC mixes were produced with cement contents of 450 kg/m 3 , 50% RCA replacement and 3% admixture while the used filler material was 0%, 10%, 20%, 30% and 40%. The effect of MP on key fresh properties such as filling ability, passing ability and segregation resistance of SCC were investigated and the effects on RCA hardened concrete such as compressive and indirect splitting strengths , abrasion resistance , Cantabro test and RCPT test to improve durability. The test result revealed that the filling ability, passing ability and segregation resistance of SCC were improved for 30% and 40% MP. The test result of hardened concrete revealed that mixes up to 20% MP give normal strength and mix with 10% MP improves durability. The overall test results suggest that using 10% MP as partial replacement of cement produce SCC without affecting the key fresh properties of concrete and improved durability.

Large and massive concrete structures with high cementitious content like foundations, tunnels, bridges, dams and hydraulic structures are subjected to cracks generated and developed by internal thermal stresses and damages due to delayed ettringite formation (DEF) associated with the hydration process of cement. The Ondes bridge, Bourgogne bridge and Saint-Maurice de Beynost bridge are international examples of concrete structures damaged by delayed ettringite formation. Due to the construction expansion in Egypt and the Middle East, it was necessary to study the effect of concrete constituents on the evolution of concrete heat of hydration and the differential temperature between the core and the concrete surface, as well as the mechanical properties such as the compressive strength. In this study, the effects of six types of cement, two water-binder ratios, with two different cement contents and supplementary cementitious materials like silica fume, fly ash and metakaolin were studied. The test results of hardened concrete showed that the blast-furnace cement and moderate heat of hydration cement had an obvious effect on the hydration heat rate and concrete compressive strength compared to other tested types. Partial replacement of cement by 50 % fly ash led to a decrease in maximum hydration temperature nearly by 13-14%. Replacement of cement by 15 % metakaolin led to an increase in maximum temperature by 2.9 % comparing to reference cement. A best thermal gradient of mass concrete was observed in case of using moderate heat of hydration cement, as the maximum temperature difference was 17.5℃.

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