Long-term properties and microstructure change of engineered cementitious composites subjected to high sulfate coal mine water in drying-wetting cycles

Abstract

The mine water environment in underground reservoirs poses great threat to the durability of artificial concrete dams, mainly due to the coupled sulfate and drying-wetting cycles. As a novel response, application of Engineered Cementitious Composites (ECC) featured by strain-hardening characteristics and inherent crack control ability in artificial dam is proposed. The special influence of simulated high sulfate mine water and drying-wetting cycle on ECC is investigated in this study, by measuring the mass and compressive properties evolvement and characterizing the microstructure and phase change. The results show that both the mass change and compressive strength of ECC specimens exhibit an initial increase followed by a subsequent decrease with extended drying-wetting cycles. Particularly, the specimens in sulfate solution show lower peak strength and sharper decline than that in tap water, which highlights the deteriorating role of sulfate attack. However, all of the stress-strain curves would eventually access a stable stage, showing toughness irrespective of the erosion ages. The micro-analysis indicates the filling effect of needle-like ettringites on the internal pores at early age. As the erosion extended, a large amount of coexistent ettringite and gypsum crystals are found responsible for the deterioration. Fortunately, the presence of microfibers mitigates the damage evolution.