氧化镁在不同水泥基中的水化和膨胀

Hydration and Expansion of MgO Hydrated in Different Cement Matrixes

The characteristics of expansion of light-burnt MgO in several pastes of cement, such as Portland cement, blended cement with 32%(wt) PFA or BFS, alkali-slag cement, aluminate cement, supersulphated cement and aluminium sulphate cement, were investigated in various conditions,and the hydration phenomena of MgO in cement pastes were studied with the help of DTA-TG and XRD technique. When MgO hydrates in the former four cement pastes, the expansion caused develops approximately in an exponential rule. MgO hydrates slowly in the pastes of aluminate cement and aluminium sulphate cement, thus the expansions are little, and the relationships between the expansion and the curing time are not exponential curves. A good correlation between the expansion and the crystals of Mg(OH)_2 formed appears to exist, even though there is not general relationship between the amount of Mg(OH)_2 formed and the extent of expansion. When the pastes are cured in water, the expansion is higher with higher temperature. The higher the alkalinity of pore solutions in cement pastes, the larger the expansion caused by hydration of MgO into Mg(OH)_2. PFA or BFS restrains the expansion.