Deterioration process of high belite cement paste exposed to sulfate attack, calcium leaching and the dual actions

Abstract

Deterioration process of high belite cement (HBC) paste with and without 30 wt.% fly ash, when exposed to sulfate attack, calcium leaching and the dual actions, was investigated by mass loss, expansion rate, porosity, corrosion depth, compressive strength and Vickers hardness, so did the contrastive ordinary Portland cement. Moreover, XRD, TGA, 29Si NMR, SEM and EDS linear scanning measurements were also conducted to assess the chemical attack mechanisms under corresponding aggressive conditions. Results showed that, the degradation of HBC pastes varied between different exposure conditions, and the most severely corroded samples were that exposed to (NH4)2SO4 solution with coupling sulfate attack and calcium leaching, which interacted with each other and accelerated the transfer process of sulfate ions to the cement matrix and calcium ions to external solution. Compared with ordinary Portland cement, high belite cement had a better corrosion resistance against the dual actions of sulfate attack and calcium leaching, and it could be further promoted by the moderate substitute of fly ash.