Recycled concrete as coarse aggregate for structural concrete production

Abstract

A new source of raw material that local batching plants can use is presented, that is the Recycled Aggregate Concrete (RAC). The use of Recycled Concrete Aggregates (RCA) in new concrete offers a solution to a problem of worldwide dimensions. That is to make construction more "green" and environmentally friendly. Some major environmental issues associated with construction are that construction "takes 50% of raw materials from nature, consumes 40% of total energy, and creates 50% of total waste" as quoted in literature. The use of RAC on a large scale may help to reduce the effects of construction on these factors by reusing waste materials and preventing more natural aggregates from being harvested. In a country like Lebanon with limited natural resources, the research holds special importance. Studies showed that quarries can annually reduce an estimated surrounding land value by 16 to 71%. The estimated number of quarries in Lebanon is about one thousand, endangering the whole country environment. The research presented examines the possibility of using recycled concrete as coarse aggregates in producing structural concrete. The effect of different percentages of RCA on the mechanical properties of concrete is studied. Five types of concrete mixtures were tested: Concrete made entirely with natural aggregate (NA) as control mix and four types of concrete made with natural fine and recycled coarse aggregate (30%, 50%, 75% and 100% replacement of coarse recycled aggregate). Recycled aggregate was obtained by crushing manually large pieces of waste concrete brought from a site in Dbayii. A total of forty specimens were tested to compare the results. All in all it is found that the use of RCA in structural concrete is viable.