Evolution and mechanism on shrinkage of high-performance concrete with full aeolian sand cured by superabsorbent polymer

Abstract

Preparing high-performance concrete with full aeolian sand (FA-HPC) can address the shortage of high-quality aggregates. Its low water-binder ratio (w/b) and high content of cementitious material content endow this concrete with great strength and durability but a high risk of shrinkage cracking. Herein, the effect of superabsorbent polymer (SAP) on the separate shrinkage of FA-HPC, and the mechanism of internal curing (IC) were investigated from various macro–micro perspectives. IC water migration was monitored via nuclear magnetic resonance (1H NMR). The results showed that autogenous shrinkage dominated the total shrinkage of the FA-HPC, accounting for 70%–80%. The SAP with medium particles effectively reduced the total shrinkage in the plastic and hardening stages, with nearly zero autogenous shrinkage at 0.3% content. From the characterization of mechanism, capillary pressure build-up of FA-HPC containing SAP was delayed with significant suppression in internal relative humidity (IRH) drop and moisture loss especially due to self-desiccation. The coupling effect of self-desiccation and evaporation triggered the nonlinear correlation between moisture loss and total shrinkage, whereas SAP amplified the proportion of drying shrinkage. Microscopically, the incorporation of SAP with IC water hindered the early hydration process but resulted in a higher final hydration degree within 72 h bringing a refined pore structure. Moreover, the adaptive release of IC water was used for hydration mainly within 72 h, and it continuously compensated for IRH drop over 28 d based on the supply–demand mechanism in FA-HPC. This study proposes a promising strategy for shrinkage resistance of FA-HPC and promotes the application of aeolian sand-based concrete.