Nanomaterials in Rubberised Concrete: A Review of Latest Research Trends

Abstract

The global push for sustainability is influencing all sectors, including construction, where the circular economy concept is gaining prominence by recycling waste materials. Waste tyres have captured significant attention from researchers as a resource for producing crumb rubber (CR), which can substitute for traditional fine aggregates in concrete. This substitution offers increased toughness, energy absorption, flexibility, and sound and heat insulation. However, the trade-off is a reduction in mechanical strength owing to inadequate bonding between CR and cement paste, attributed to the hydrophobic nature and softness of rubber particles compared to sand. Additionally, using CR increases matrix porosity. Various efforts have been made to address these challenges, and incorporating nanomaterials is one promising approach. This paper provides a concise review of the application of nanomaterials in rubberised concrete (RC) to mitigate the issues associated with CR in cementitious composites. It aims to serve as a quick guide for researchers interested in exploring nanomaterials in RC, offering insights into recent trends and the types of nanomaterials utilised in current research. The most commonly used nanomaterials in RC include graphene oxide (GO), graphene nanoplatelets (GNPs), nano silica (NS), carbon nanotubes (CNTs), nano iron oxide (NIO), and nano titanium dioxide. Due to differences in size and morphology, these nanomaterials enhance RC through distinct mechanisms. Zero-dimensional (0D) nanomaterials like NS act as nanofillers and reactive pozzolans, while one-dimensional (1D) nanomaterials such as CNTs can fill nanovoids and bridge microcracks. GO, a highly reactive two-dimensional (2D) nanomaterial, not only promotes cement hydration by acting as nucleation sites but also bridges across cracks, preventing their propagation. Additional nanomaterials that warrant further exploration in RC include carbon nanofibers, carbon black, nano calcium carbonate (CaCO₃), and innovative waste-based nanomaterials.