International Science and Technology Journal

Large area in Libya is witnessed accumulation of huge amounts of concrete debris, a result of demolition works, especially in recent years. these wastes can cause many environmental problems and took forms of normal concrete, bricks and tile as well as waste reinforced concrete. This study was capable of achieving the research objectives of the work plan, which included the effect of the strength of recycled coarse aggregate on the strength and workability of RAC. The recycled coarse aggregate was produced by the crushing of old concrete from old construction works (demolition wastes) in the laboratory. In this research, one series of concrete mixtures were prepared, in which the coarse recycled aggregate was used as 0%, 05%, 10%, 15%, 20%, 25%, 30% and 50% replacements of coarse natural aggregate. The results indicated that the brief analysis of properties of coarse recycled aggregates and judged its effectiveness in use of concrete. This has been confirmed by the results of the aggregates tests. The concrete mixes were designed using absolute volume method, concrete mixes were designed with 28-day compressive strength as 30 MPa. From here, a new relationship between the percentage of recycled aggregates and the new concrete properties. The results of test show that it could recycled aggregate contents have improved of the compressive strength and workability to reach the more level of natural aggregate concrete for using (5~15) % of recycled aggregate replacement. The indirect tensile strength of concrete increases at all percentage of recycled aggregate for natural aggregates.