Hybrid high calcium fly ash alkali-activated repair material for concrete exposed to sulfate environment

Abstract In this paper, the performance of hybrid high calcium fly ash (FA) alkali-activated repair material for concrete exposed to sulfate environment was studied. The high calcium fly ash (FA) was replaced with ordinary Portland cement (OPC), basalt fiber (BF) and silica fume (SF). The repair mortars were prepared with AAMs and river sand at sand/binder ratio of 1. The mixtures were activated with 14 M sodium hydroxide (NH) and sodium silicate (NS) using NS/NH ratio of 2.0, and liquid/binder ratio of 0.6. Compressive strength and weight losses after immersion in 5% MgSO4 solution of AAM samples were tested. In addition, the slant shear samples were also prepared for the shear bond strength test after immersion in 5% MgSO4 solution. For comparison, two commercial repair non-shrink cement grouts were also tested. The results showed that the AAM hybrid with 10%OPC outperformed the AAM hybrid with BF and SF and the strength and weight loss were comparable to the two tested commercial non-shrink cement grouts.