早龄期混凝土抗裂性环形试验研究进展

OVERVIEW OF RING TEST TO ASSESS CRACKING RESISTANCE OF EARLY-AGE CONCRETE

  • 摘要: 早龄期混凝土极易在限制收缩条件下产生裂缝进而影响结构的安全性、耐久性和适用性,因此提供一种简单有效的方法来评估早龄期混凝土在限制收缩条件下的抗裂性,就显得非常重要. 由于能够提供一定的约束刚度并易于实验室操作,限制收缩环形试验被广泛应用到混凝土在限制收缩条件下的抗裂性评估. 主要从限制收缩环形试验的发展、破坏机理、影响因素三方面进行阐述. 通过限制收缩环形试验进行不同目的的混凝土试验研究,推动了限制收缩环形试验的不断发展;破坏机理主要有最大拉应力理论以及基于断裂力学的断裂能机制预测混凝土的开裂;环形试验的影响因素主要有试件几何尺寸,边界条件,混凝土材料性能以及预制裂缝四个方面. 最后介绍了一种椭圆环试验方法,可有效评估高约束度下混凝土的抗裂性.

     

    Abstract: The early-age concrete under the condition of restrained shrinkage is easy to crack, which would affect safety and durability of the structure, as well as the applicability. So it is very important to provide a simple and effective method to assess the crack resistance of the early-age concrete. In view of providing certain rigidity and the convenience of laboratory constraints, the restrained shrinkage ring test is widely used to evaluate the crack resistance of the concrete under restrained shrinkage conditions. This paper discusses the development of the restrained shrinkage ring test, the failure mechanism and the impact of three factors. The restrained shrinkage ring test is recommended as a standard test method by the American Association of State Highway and Transportation Officials (AASHTO) and the American Society for Testing and Materials (ASTM), and the test is conducted for different purposes, including the failure mechanism based on the maximum tensile stress fracture mechanics theory and the fracture energy to predict the concrete cracking. The annular test specimen geometry, the boundary conditions, the performance of the concrete materials and the pre-crack are considered as influencing factors. A test method of elliptical ring is adopted, which can effectively assess the crack resistance of the concrete under conditions of high degree of restraint.

     

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