Influence of Fly Ash on Chloride Ion Penetration and Diffusion in Cement Paste

In this paper,the effects of fly ash on Cl-penetration and diffusion of cement-stone in different hydrate stages are studied by modified ASTM C1202 test. Pore structure for cement-stone,morphology and chemical composition of hydration products are investigated by mercury intrusion porosimetry,scanning electron microscope and energy dispersive spectroscopy. Results show that:on the condition of accelerated curing 60 ℃,the secondary pozzolanic reaction could be excitated in earlier hydrate stage,and it could form abundant alveolate hydration products; after 28 d of hydration,porosity of cement paste would be turned down by doping in fly ash,forming more close-grained hydrate structure,so the impermeability of Cl-in cement paste could be boosted.