Overview of the Mechanical Properties of Concrete Incorporating Waste From the Concrete Industry as Aggregate

Millions of tons of construction and demolitions wastes (CDW) are generated annually by the concrete industry, and these wastes most times end up in landfills where they contaminate the environment. As the global demand for concrete increases with a consequential increase in the consumptions of its components, the use of alternative materials as components in concrete will create a pathway to meet the future demand for concrete. One of the sustainable way forward is replacing the most voluminous component of concrete (i.e. aggregates) with CDW. However, in order to use CDW as aggregate, it needs to undergo processing which turns it into recycled aggregate. Mechanical properties of concrete are greatly affected by the components in concrete, and the replacement of natural aggregates with processed CDW is expected to alter the resulting properties of concrete. Though there are several contradicting conclusions in the literature which might be as a result of different sources and properties of CDW (i.e. recycled aggregate) used. This overview showed that processed CDW can be used successfully as aggregate in concrete to achieve similar/higher strength compared to those made with natural aggregate. But the proper treatment of the recycled aggregate and/or additions such as incorporation of supplementary cementitious materials have to be made. Also, the use of alternate binders such as alkali-activated materials with recycled aggregate can be used to achieve enhanced mechanical properties. In conclusion, the use of these wastes as aggregates in concrete will help to prevent more exploitation of natural deposits of aggregates alongside with reducing the overall cost of the concrete.