自密实混凝土断裂性能的试验研究

Experimental study on fracture properties of self-compacting concrete

在混凝土三点弯梁断裂试验研究中,对双K断裂参数模型试验进行了简化,通过应力控制加载方式测量应变,利用试件变形的三角形比例关系求得裂缝口张开位移.对C35与C50自密实混凝土断裂性能的试验研究表明,自密实混凝土的断裂性能与相同强度等级的普通混凝土相比有所降低;自密实混凝土的失稳断裂韧度随龄期近似线性增长,起裂韧度一开始增长较快,随后增长速度有所减缓;自密实混凝土断裂参数和抗压强度之间存在近似线性关系.提出的简化方法有较高的精度,可以为自密实混凝土断裂性能研究与实际工程应用提供可靠的参考.

The fracture properties of self-compacting concrete and normal concrete in strength grade of C35 and C50 were investigated in three-point bending tests with a simplified double-K fracture parameter model. In the tests, the strain was measured by the stress-controlled loading process and the crack mouth opening displacement was calculated according to the triangle relationship between the measured strains of different parts of specimen. The experimental results show that the fracture properties of self-compacting concrete are lower than those of the normal concrete. The unstable fracture toughness of self-compacting concrete increases near-linearly with the age, which increases rapidly at the beginning and slows down afterwards. And there is a good linear relationship between the fracture parameters and the compressive strength of self-compacting concrete. The simplified test model has a quite high accuracy, and it is credible for the studies on the fracture properties of self-compacting concrete and the practical engineering application.