Effects of moisture gradient of concrete on fracture process in restrained concrete rings: Experimental and numerical
Effects of moisture gradient of concrete on fracture process in restrained concrete rings: Experimental and numerical
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DOI：
10.1016/j.engfracmech.2019.01.011
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发表时间：
2019-03
影响因子：
5.4
通讯作者：
W. Dong;Xiaoyu Zhao;Xiangming Zhou;Wenyan Yuan
中科院分区：
文献类型：
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作者：
W. Dong;Xiaoyu Zhao;Xiangming Zhou;Wenyan Yuan
混凝土中水分梯度引起的不均匀收缩提供了自我约束，这对于通过约束收缩环试验评估混凝土的开裂潜力具有显着效果。此外，混凝土的湿度梯度也会受到混凝土强度的影响，因为不同强度等级的混凝土通常具有不同的水灰比。本文对壁厚为 37.5mm 的三个系列圆形和椭圆形混凝土环以及 C30、C50 和 C80 三个不同混凝土强度等级进行了测试，以研究湿度梯度对约束混凝土环中裂纹萌生和扩展的影响。引入基于非线性扩散理论的集成模型来计算混凝土环中的水分分布，并推导虚拟温度场来模拟混凝土的收缩效应。同时，提出了一种基于断裂力学的数值方法来分析约束环试验中混凝土环的裂纹萌生和扩展。详细阐述了环几何形状、混凝土强度和均匀/非均匀收缩假设对裂纹萌生和扩展过程的影响。结果表明，混凝土的不均匀收缩为混凝土开裂提供了驱动能量，约占总驱动能量的40%。因此，它显着影响裂纹萌生位置和扩展方向，裂纹发生在混凝土环的外表面并向内表面扩展。随着混凝土强度的增加，约束混凝土环的开裂可能性增大，并且由于水分分布减少，由不均匀收缩引起的自约束在总约束中所占的比例减小。
The non-uniform shrinkage caused by moisture gradient in concrete provides self-restraint, which has a significant effect on the assessment of cracking potential of concrete through the restrained shrinkage ring test. Furthermore, moisture gradient in concrete would be also affected by concrete strength because concretes designed for different strength grades usually have different water to cement ratio. In this paper, three series of circular and elliptical concrete rings with a 37.5 mm thick wall and three distinguished concrete strength grades of C30, C50 and C80 were tested to investigate the effect of the moisture gradient on crack initiation and propagation in restrained concrete rings. An integrative model based on the nonlinear diffusion theory is introduced to calculate the moisture distributions in concrete rings, and the fictitious temperature fields are derived for the simulation of the shrinkage effect in concrete. Meanwhile, a fracture mechanics-based numerical method is proposed to analyze the crack initiation and propagation in a concrete ring in the restrained ring test. The effects of ring geometry, concrete strength and uniform/non-uniform shrinkage assumption on the cracking initiation and propagation process are elaborated. The results indicate that the non-uniform shrinkage in concrete provides driving energy for concrete cracking, which is approximately 40% of the total driving energy. Accordingly, it significantly affects the crack initiation position and propagation direction, occurring at the outer surface and propagating toward the inner surface of the concrete ring. With the increase of concrete strength, the cracking potential of restrained concrete ring increases and the proportion of the self-restraint caused by the non-uniform shrinkage in the total restraint decreases because of the reduced moisture distribution.