Effect of recycled concrete aggregate on the mechanical properties of concrete

Abstract

Over 25 billion tons of concrete are used worldwide every year which makes it the most used construction material in the world. Therefore, the high demand on natural aggregate used in concrete, forced people to find an alternative green material. Researchers found an alternative environmental material that is recycled concrete aggregate. Recycling demolished concrete waste can provide sustainable green solution. The simple act of recycling the concrete diminishes the quantity of material that must be land-filled. The concrete itself becomes aggregate and any embedded metals can be removed and recycled as well. As space for landfills gets to be premium, this decreases the requirement for landfills, as well as reducing the economical impact of the project. Furthermore, using recycled concrete reduces the need for natural aggregates. Therefore, the environmental impact of the aggregate extraction process is reduced. In addition to that, recycled concrete aggregates absorb a big amount of carbon dioxide from the surrounding environment. This research analyzes the possibility of using recycled concrete as coarse aggregate to produce structural concrete. Five types of concrete mixtures were tested: One mixture was entirely made of natural aggregate which is considered as a as a control concrete. The other four mixtures were made from natural sand and recycled coarse aggregate with four percentages of replacement 30%, 50%, 75% and 100%. Recycled aggregates were obtained from the demolished concrete cylinders that were originally brought to the civil engineering laboratory at UOB to be tested for their compressive strength. A total of sixty specimens were tested to study the effect of RCA on the mechanical properties of concrete. After taking everything into consideration, the use of recycled concrete aggregate in structure is practical.