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

本文探讨了MgO在硅酸盐水泥、矿渣水泥、粉煤灰水泥、碱-矿渣水泥、铝酸盐水泥、石膏矿渣水泥和硫铝酸盐水泥浆体中的膨胀特性,并借助于DTA-TG和XRD对MgO的水化现象进行了研究.结果表明,MgO在前四种水泥浆体中水化所产生的膨胀近似呈指数规律发展,而在铝酸盐水泥和硫铝酸盐水泥浆体中水化缓慢,膨胀较小,且不遵循指数规律;膨胀起因于Mg(OH)_2晶体的生成,浆体孔隙液的碱度促进MgO水化产生的膨胀;粉煤灰和矿渣能抑制膨胀;水中养护时,提高温度有利于膨胀.

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.