Effect of recycled course aggregate from concrete debris on the strength of concrete

Abstract The paper investigates the fresh and hardened mechanical properties of a concrete mix produced with partial or full substitution of natural aggregates with recycled aggregates from demolition works and crushed tested cubes concrete from laboratory. Recycled aggregate concrete (RAC) is the concrete that has been made from waste materials recycled as coarse and/or fine aggregate. One of the waste materials is the concrete that is taken from demolished buildings in Iraq due to military operations on 2014 and the other is crushed tested concrete cubes from laboratory. Choosing crushed concrete wastes from demolition works and crushed test cubes concrete from laboratory as source of recycling would result in reusing portion of the waste products of the concrete production industry. This study presents an experimental study on the performance of concrete that contains recycled coarse aggregate. The replacement percentages of natural coarse aggregate with the recycled coarse aggregate are (0, 33.3, 66.7 and 100) %. Moreover, silica fume was used as an admixture for all recycled aggregate concretes. Compressive and indirect tensile strength were studied for all of the reference and recycled aggregate concretes at (28) days age, by testing concrete cubes and cylinders specimens respectively. The results showed that the compressive strength and splitting tensile strength decreased for recycled waste concretes taken from demolished buildings and increased for recycled crushed tested cubes concretes from laboratory as compared to the reference concrete. When the silica fume was added, the compressive strength and tensile strength increased for all recycled aggregate concretes compared to those without the silica fume.