Thermal Performance of Geopolymer Concrete Energy Piles

Abstract This study evaluates the thermal performance and environmental impacts of energy geo-piles constructed using geopolymer concrete (GPC) incorporating 30% electric arc furnace slag (EAFS), in comparison with conventional ordinary Portland cement concrete (OPCC). The study involved comprehensive experimental testing and numerical modelling to assess heat-transfer efficiency, thermal deformation characteristics, and the carbon footprint of each material system. Two full-scale prototype piles were built and tested; one made from EAFS-GPC and the other from OPCC. Both concrete types exhibited comparable mechanical performance. Results show that piles constructed using EAFS-GPC exhibited higher thermal conductivity, resulting in a 14% improvement in the heat-transfer efficiency compared with the measurements recorded on the OPCC pile. In addition, the thermal expansion coefficient of EAFS-GPC piles was 17% lower than that of the normal Portland concrete pile, thereby reducing susceptibility to lateral earth pressures. The surrounding soil reached an 8% higher steady-state temperature, indicating more efficient heat exchange. Importantly, the use of GPC led to a 45% reduction in CO 2 emissions, demonstrating significant environmental benefits. The numerical model results were in close agreement with the laboratory measurements, with a maximum deviation of 7.2%. The study findings confirm that EAFS-enhanced GPC is a high-performance, low-carbon material for next-generation energy geo-piles, with optimal behaviour achieved when the pile thermal conductivity matches or exceeds that of the adjacent soils.