Beneficial utilization of recycled asphaltic concrete aggregate in high calcium fly ash geopolymer concrete

In this paper, the utilization of recycled asphaltic concrete aggregate (RACA) in high calcium fly ash geopolymer concrete (HFGC) was explored. Coarse limestone aggregate was replaced with RACA at 0, 20, and 40 %by weight of the aggregate. The 10 M NaOH (NH), sodium silicate (NS), NH/NS ratio of 1.0, liquid alkaline/ash ratios of 0.45, 0.55, 0.65 and 0.75 were used to make geopolymer concrete cured at 25 degrees C. Test results indicated that the compressive strength decreased with the increase in RACA content as expected. However, the surface abrasion and sulfuric acid resistances were improved due to the presence of the adhered asphalt and the associated reduction in porosity and water absorption of the HFGC. The other benefit is the reduction in thermal conductivity due to the intrinsic low thermal conductivity of asphalt and RACA. The RACA could thus be beneficially utilized to improve the performance of geopolymer concrete with slight reduction in compressive strength but enhanced surface abrasion and sulfuric acid resistances.

Automated summary

This study demonstrates that using recycled asphaltic concrete aggregate (RACA) can improve the surface abrasion and sulfuric acid resistances of high calcium fly ash geopolymer concrete (HFGC), while reducing the thermal conductivity.