Recycling potential evaluation of geopolymer concrete with different cementitious system used in freeze-thaw environment

Geopolymer concrete (GPC) is a promising alternative to Ordinary Portland cement concrete (OPC), with great potential in reducing carbon emissions and energy consumption. However, current mix proportion designs overlook the recyclability for future applications. This study aims to explore the recyclability of GPC in freeze-thaw environment. Different precursors (fly ash, metakaolin, red mud, and slag) were used to prepare GPC with the comparable strength level. To enhance the frost resistance of GPC, slag was implemented to replace 40 % of the precursors. After 350 rapid freeze-thaw cycles, the GPC specimens were crushed and screened to obtain recycled geopolymer coarse aggregates (RGA), and the physical properties of RGA were investigated. The results showed GPC demonstrated excellent frost resistance, withstanding up to 350 freeze-thaw cycles, except for fly ash-based GPC which failed after 150 cycles. After 350 freeze-thaw cycles, metakaolin-based, red mud-based and slag-based GPC still met the requirements of 50 years' service life in cold regions. The physical properties of RGA recycled from the GPC could meet the quality standards for Class II recycled aggregate, highlighting the promising recyclability of GPC in freeze-thaw environment. It was worth noting that the quality of recycled aggregate depended on the performance of the parent concrete.