Deficits in the performance of recycled aggregate concrete, typically made from construction and demolition waste, has led researchers to examine the use of a variety of additives to improve strength and tensile properties. Ibtisam Abbasi reviews a series of recent studies examining the use of nanomaterials such as calcium carbonate, titanium and carbon nanotubes to improve recycled aggregate concrete performance.



The new era of sustainable eco-friendly manufacturing has shifted all industries towards carbon neutrality, especially the concrete industry. Recycled aggregate concrete (RAC) is an essential product in this regard. However, several shortcomings in its performance have encouraged researchers to investigate the effects of various additives.


An Overview of Recycled Aggregate Concrete (RAC)

As per the latest research published in the Journal of Cleaner Production, the construction industry accounts for the use of around 40% to 60% of natural resources, and construction and demolition (C&D) waste is about 35% to 40% of total worldwide waste. Excessive resource consumption and a persistent rise in the volume of C&D waste are serious threats to the sustainable construction industry.

Recycled aggregate concrete (RAC) is typically concrete made from C&D waste that partially or entirely substitutes traditional natural aggregates (NAs). As per the British standard BS 8500-2 (BSI, 2006), RCA is defined as recycled aggregates with maximal masonry/fines composition of 5%, 0.5% maximum elemental composition of lightweight material/asphalt, and a maximum limit of 1% other foreign materials.


Need for Modification of RAC

A considerable number of previous investigations have shown that RCA has a detrimental influence on concrete properties and performance in contrast to NA concrete.

The concrete manufactured with natural aggregates is much superior in terms of strength and tensile properties. The poor qualities of waste aggregates with bonded mortar on the surface are the core reason for the decline in the performance of recycled aggregate concrete. This necessitates the modification of the RAC substance.