大体积补偿收缩混凝土中延迟钙矾石生成产生危害的条件

研究了大体积补偿收缩混凝土中延迟钙矾石生成可能对混凝土产生危害的条件，用步进扫描半定量XRD法确定水化产物的物相组成，同时测定胶砂试件的限制膨胀率，遭受过早期高温的补偿收缩混凝土对于长期使用过程中环境的湿度变化情况比较敏感，只有在适当的湿度条件下养护，才能获得适量的膨胀，以补救早期膨胀损失所造成的不利影响，养护环境过于干燥或过于潮湿，有可能导致遭受过早期高温的补偿收缩混凝土结构收缩开裂或膨胀破坏。

PRFCONDITIONS OF THE HARMFUL EFFECT INDUCED BY DELAYED ETTRINGITE FORMATION IN MASSIVE SHRINKAGE-COMPENSATING CONCRETE

The preconditions of the harmful effect induced by delayed ettringite formation (DEF) in massive shrinkage-compensating concrete whose binder is composed of portland cement and expansive agent were studied. The phase composition of hydration product was determined with semi_quantitative step_scanning XRD and the restrained expansion of mortars was measured. It is found that the shrinkage-compensating concrete going through high temperature in the early age was sensitive to the environmental humidity alternation in the later stage. Only cured in an appropriate humid condition, an appropriate expansion of mortars with suitable strength can be obtained to remedy the adverse effect of the expansion loss in the early age. It is important to note that the shrinkage-compensating concrete structure that goes through high temperature in early age and is cured in undue dry or humid environment in later age may suffer shrinkage cracking or expansion damage. In high strength concrete, especially, only a small quantity of later formed ettringite in the dense paste can induce concentration of stress and results in cracking of concrete. It is very important for the construction of massive shrinkage compensating concrete that effectively controlling the core temperature of concrete under a threshold.