轻集料混凝土干燥收缩影响因素及开裂评价方法

Influencing Factors and Evaluation Methods for Shrinkage and Cracking of Light Weight Aggregate Concrete

采用测试内约束收缩应力的方法研究了表观密度、水灰比、轻集料品种、不同矿物掺合料及约束程度对轻集料混凝土干燥收缩开裂的影响。结果显示,轻集料混凝土表观密度的降低增大了干燥收缩开裂的趋势,过低或过高的水灰比对干燥收缩开裂均有不利影响,轻集料种类则对收缩应力有一定影响;粉煤灰、磨细矿渣粉、硅灰的掺入降低了收缩开裂风险,混凝土收缩开裂概率随着约束程度提高明显增大。

By using of the method of measuring the contracted stresses in restraint condition the influences of several factors, including apparent density, water cement ratio, type of lightweight aggregate, different mineral admixture and restraint degree, on the shrinkage cracking of lightweight aggregate concrete were studied by tests. And the rezults show that, the decrease of apparent density of lightweight aggregate concrete can increase the risk of dry shrinkage cracking, and too low or too high water/cement ratio also has negative influence on preventing the dry shrinkage cracking. The type of light aggregate has some effects on the shrinkage stress. The addition of fly ash, ground slag powder and silica fume will reduce the risk of shrinkage and cracking. And the cracking probability increases obviously with the increasing restraint degree.