Long term durability at 40 deg C of ecoefficient belite cement-mortar exposed to sulfate attack

摘要

The durability of cement-based materials with respect to exterior aggressions is one of the current priorities in civil engineering. Depending on their use, the cement-based materials can be exposed to different types of aggressive environments. For instance, damage to concrete structures in contact with a sulfate and saline environment are of most importance. Belite cements have excellent durability against determined expansive attacks and lower heat of hydration than that of Portland cements. These properties convert belite cements into good candidates for the immobilisation of low-level liquid waste and medium-level liquid waste. In this work, the authors present a long-term durability study at 40 deg C of a kind of belite cement from coal fly ash class C as alternative raw material. The aggressive was a 0.5 mol/l sodium sulfate (Na_2SO_4) solution, which is common in some evaporator concentrate solutions of medium-level liquid waste and low-level liquid waste. The attack was evaluated by means of flexural strength changes of mortars over 180 days. Furthermore, the changes in microstructure were followed by mercury intrusion porosimetry and mineralogy by X-ray diffraction.