Development of recycled aggregate concrete with ground granulated blast-furnace slag and hybrid fibres for pavement applications

Increasing demands for sustainable construction practices highlight the need for alternative materials in concrete production, particularly for infrastructure projects such as pavements. In this study, the mechanical performance and environmental impacts of recycled aggregate concrete (RAC) reinforced with hybrid fibres (HFs) for rigid pavement and ultra-thin whitetopping applications were investigated. Recycled concrete aggregates (RCA) are a promising alternative to natural aggregates (NA), but their incorporation in concrete often leads to inferior mechanical properties. Using RCA along with ground granulated blast-furnace slag (GGBS) as a partial cement replacement, the aim of this research was to enhance the performance of RAC. The hybrid combination of macro and micro fibres could also enhance the mechanical properties of RAC by means of its synergistic action. Therefore, two HF combinations – macro steel fibres with micro polypropylene fibres and macro steel fibres with micro glass fibres – were examined. The experimental results demonstrated that HFs and GGBS significantly enhanced the performance of RAC when compared with NA concrete. Furthermore, life cycle assessment indicated reductions in carbon dioxide emissions and cumulative energy demand for pavement sections using the developed concrete mixtures. The findings suggest that integrating HFs, RCA and GGBS offers a viable path toward producing high-performance, sustainable concrete for pavement applications, balancing both structural and environmental benefits.