Influence of reclaimed asphalt pavement aggregate on the performance of metakaolin-based geopolymer concrete at ambient and elevated temperatures

Abstract

Considering the environmental concerns surrounding conventional cement concrete production and the increasing demand for more sustainable and green materials, recent research considered utilization of recycled waste materials (e.g., aggregates from concrete construction and demolition, and reclaimed asphalt pavement) as full or partial substitutes for natural aggregates. Another direction of the research considered the production of more sustainable binders as an alternative to conventional cement (e.g., geopolymer or alkali-activated materials).To serve the objective of utilizing waste materials and reducing negative environmental impact associated with the use of cement concrete, the present study investigated the potential of producing metakaolin-based geopolymer concrete incorporating reclaimed asphalt pavement (RAP) aggregate. This research comprised experimental testing of five concrete mixes with 0%, 25%, 50% and 100% coarse RAP aggregate replacing the natural aggregate. Tests included compressive stress–strain behavior at ambient conditions (i.e., compressive strength, elastic modulus, strain at peak strength and toughness), and flexural strength. The performance after heat exposure to elevated temperatures of 300 °C and 600 °C was also tested. Proposed models for predicting the elastic modulus, strain at peak strength, flexural strength, and compressive stress–strain relationship matched the experimental results well. Results indicated that natural aggregate replacement by 25 % RAP aggregate caused a reduction in the compressive and flexural strengths by 42.8% and 26.2%, respectively. The increase in the RAP aggregate content enhanced the strain at peak strength e.g., the strain at peak strength was 42.9% higher than the control mix when 100% RAP aggregate was utilized.