Investigation on crack resistance of full aeolian sand high-performance concrete synergistically modified by supplementary cementitious materials and superabsorbent polymer

The development of full aeolian sand high-performance concrete (FA-HPC) can alleviate the dilemma of river sand shortage. However, the high cracking potential appears due to the characteristic of low water-to-binder ratio and high cementitious materials content. Herein, supplementary cementitious materials (SCMs), i.e., fly ash and silica fume, and superabsorbent polymer (SAP) are used to optimize the crack resistance synergistically. The crack resistance in plasticity and hardening stages are investigated based on flat plate cracking and ring restrained cracking combined with chloride ions penetration, respectively. Meanwhile, capillary pressure, mechanical strength, and internal temperature field were also involved. Additionally, the modification mechanism of SCMs and SAP is analyzed from a microscopic perspective via hydration heat, phase analysis, and microstructure. The results showed that whether single use or binary mixing, fly ash and silica fume significantly improved the crack resistance of FA-HPC. Moreover, it was further enhanced by the SAP, presenting a 63.39% and 96.96% increase in crack resistance at plasticity stage and hardening stage respectively as well as a 78.31% reduction in chloride ions penetration. Contrary to silica fume, fly ash hindered early hydration leading to a decrease in capillary pressure, strength, and internal temperature field with content dependence. Besides, the most intense volcanic ash reaction was observed in binary mixing. Although SAP delayed the early hydration, the later hydration degree was improved obtaining more hydration products at 28d since the internal curing effect. Thereby, the more refined microstructure was achieved for more optimized crack resistance. This study provides an available strategy for reducing the cracking risk of FA-HPC to promote wide application in engineering.