Improving the Volume Stability of Low-Carbon Ultra-High Performance Concrete Through the Employment of Internal Curing

High-volume fly ash binder and aeolian sand have been widely used in the production of low-carbon ultra-high performance concrete (UHPC) owing to their environmental and economic benefits. However, such low-carbon UHPC still faces the volume stability issues, including autogenous shrinkage, drying shrinkage and early-age cracking. In this study, a superabsorbent polymer (SAP) was incorporated into low-carbon UHPC containing high-volume fly ash and aeolian sand to improve its volume stability through internal curing. The effects of SAP particle size and dosage on the mechanical properties and volume stability of low-carbon UHPC were investigated. Results showed that the addition of 0.3% SAP with a particle size of 180–600 μm significantly reduced shrinkage and early-age cracking while maintaining the compressive strength. Furthermore, the microstructure of low-carbon UHPC was characterized using advanced techniques to shed light on the underlying mechanisms.