Long-term performance of moderate heat Portland cement with double-expansive sources

The long-term performance of moderate heat Portland cement with double-expansive sources (DE cement) in the system of high MgO clinker and gypsum was studied by XRD, SEM/EDAX and test methods for strength and expansion of cement. Results indicate that the periclase particle, whose size was 5–7.5 μm in DE cement clinker containing 4.8 % MgO, existed individually. The periclase hydration in hardened DE cement paste started at about 60 days and completed up to 2 000 days, and ettringite in the paste was stable from 3 days to 2 000 days. Under the conditions of 4.5%–5.0 % MgO in clinker and 2.8%–3.4 %SO3 in cement, ettringite expansion and brucite expansion in DE cement paste had a continuity, entirety and stability. At the ages of 90, 365, 730 and 2 000 days the expansion of the paste reached 0.07%–0.11%, 0.16%–0.21%, 0.21%–0.27 % and 0.29%–0.38 %, respectively. The results suggest that by using this cement in mass concrete it may compensate its temperature shrinkage and autogenous shrinkage to some extent.