Influence of ion chelator on pore structure, water transport and crack-healing properties of cement pastes incorporating high-volume fly ash and blast-furnace slag

Abstract

This paper focuses on the influence of ion chelator (CA) on pore structure, water transport and self-healing ability of cement pastes incorporating high content fly ash (FA) and blast-furnace slag (BFS). The pore structure of pastes was measured by low-field nuclear magnetic resonance (LF-NMR). The water transport property was tested by water absorption test. The self-healing ability was assessed by water permeability and crack healing test. Results showed that the compressive strength of hardened pastes was promoted by CA, the increase rates in compressive strength of pastes were 21.9% (50%BFS), 15.7% (pure cement), 9.9% (30%FA) and 8.8% (16%FA24%BFS). CA decreased the proportion of small capillary pores (0.01–0.1 μm) in cement pastes which were more pronounced for the water absorption, the reduction rates of small capillary pores were 49.0% (50%BFS), 41.5% (pure cement), 20.2% (30%FA) and 13.0% (16%FA24%BFS). The self-healing performance of pastes with 50% BFS was most obviously improved that crack with width of 0.43 mm could be completely healed within 21d, while the relative water permeability coefficient dropped by around 80%, followed by pure cement, 30%FA and 16%FA24%BFS pastes. Notably, the morphology of the crack healing product in the blend pastes with FA and BFS was changed with the addition of CA, a large amount of lumpy and clustered calcite was generated, which promoted the compactness and content of healing products. The results of this study showed that CA could significantly improve pore structure, water transport and self-healing properties of high-volume BFS cementitious materials, which meant that CA had a better application prospect in high-volume BFS cement-based materials.