高强与高性能混凝土温湿度场应力分析

Temperature analysis and humidity stress for high-strength and high-performance concrete

针对高强与高性能混凝土易于开裂的特点 ,对高强高性能混凝土早期温湿度场随龄期发展的分布情况以及混凝土的收缩变形进行理论分析 ,建立相应的计算模型 ,编制三维有限元程序 ,分析在外界温湿度变化以及不同养护条件下由混凝土内部温差和湿度变化产生的温度应力和干燥收缩应力 。

Based on the easily cracking property of high-strength and high-performance concrete, the present paper has made a theoretical analysis on temperature gradient and humidity gradient, which serve as the essential factors viable for the concrete cracks. As is known, the water-to-binder ratio of high strength and high performance concrete is rather low with the hydration of cementitious materials being fast, which accelerates the quick exhaustion of the free water in the concrete. But since the microstructure of the concrete is highly compact in nature, it is difficult for the outside humidity to be made up for. Thus, the auto-desiccation of high strength and high performance concrete is serious, which is likely to cause great autogenous shrinkage and cracks in early stage. To solve the problem, we have studied the temperature and moisture distribution with the age of the concrete and its shrinkage deformation. Based on above theory, we have established the corresponding computational model and worked out a three-dimension finite element procedure 3C3D(Concrete Cracking Control 3D)for the analysis of the temperature stress and the drying shrinkage stress due to the different interior temperature and the changes of humidity under the condition of variant environment temperature. Our experiment results show that the temperature of the concrete slab surface changes with that of the environment. However, since the temperature conduction of inner concrete is poor and when the environment temperature suddenly drops, big temperature gradient will be brought about, which may lead to a tensile stress along the thickness of the concrete slab. Nevertheless, since the humidity change goes mainly on the concrete surface, no change or little change would happen inside. The difference of humidity between the surface and the inside may result in great shrinkage stress in the surface layer of the slab, which is viable for the occurrence of crack. According to the above study, measurements are presented in this paper to strengthen the crack-resistance performancr of high-strength and high-performance concrete from the point of view of construction curing method.