等强度条件下粉煤灰掺量对混凝土抗裂性的影响

Influence of Content of Fly Ash on Crack Resistance of Concrete under the Condition of Equivalent Strength

为考察等强度条件下粉煤灰掺量对混凝土抗裂性的影响,通过调整水胶比对15%、20%、25%三种粉煤灰掺量的混凝土进行了等强度设计,并在此基础上开展了胶凝材料水化热及混凝土极限拉伸值、干缩、自生体积变形等热学性能和变形性能测试。结果表明,通过调整水胶比得到的三种粉煤灰混凝土的抗压强度、轴向抗拉强度和抗拉弹性模量基本相当,实现了等强度设计;等强度条件下粉煤灰掺量提高,混凝土的极限拉伸值增加,干缩值降低,自生体积收缩变形减少,开裂敏感性降低;三种混凝土之间的绝热温升差异小于胶凝材料水化热的测试情况,说明孤立地由胶凝材料水化热来评价混凝土的抗温度应力开裂性能是不合适的。

To evaluate the influence of content of fly ash on crack resistance of concrete under the condition of equivalent strength, three kinds of concrete respectively with fly ash content of 15% ,20% and 25% were equivalent strength designed by adjusting water-binder ratio, and the hydration heat of cementitious material, uhimate tension, drying shrinkage, autogenous volume deformation of concrete were tested. The results indicate that compressive strength, axial tensile strength, tensile elastic modulus of these three concretes are almost the same, and the design of equivalent strength is realized. When the content of fly ash is increased, concrete has larger ultimate tension, lower dry shrinkage, less shrinkage of autogenous volume deformation and lower cracking sensitivity. The differences of adiabatic temperature rise among three concretes are less than that of the results coming from hydration heat of cementitious materials, which prove that evaluating crack resistance of temperature stress of concrete only by hydration heat of cementitious materials is unsuitable.