Study On Temperature Stress And Crack Propagation Of Mass Concrete

Releasing steam heat from the mass concrete structures while solidifying leads to produce the temperature change and shrinkage. They cause the corresponding stresses which are the main factors to from crack in the mass concrete structures. It isobvious for crack to destroy the completeness and durability of the structures and to become a hidden peril of the structures. Thus, crack control must be considered while a mass concrete structure is in construction. As the variety of mass concrete application and its complexity, the cracking of mass concrete is occurring at large. These problems request us to do more researches on cracking mechanism, cracking development and cracking control methods.The key to control temperature cracks effectively lies in the precise prediction of temperature field and stress field. This dissertation simulate the transient temperature field and stress field by the means of the heat transfer theory and thermoelasticity, and found the chief influencing factor for the temperature stress of massive concrete. Based on the former fruits of temperature control and cracking prevention, the temperature stress, cracking causes and cracking control measures are studied from the macro-aspects such as: raw materials, mix ratio, additives and construction technology, and also from the micro-structure of concrete. The effect of the combination of temperature stress and the multi-stress caused by the dry shrinkage, self-shrinkage, temperature shrinkage and plastic shrinkage is considered. Then this paper conclude the measures of crack control.In addition, concrete is uneven, unlinear and anisotropic because of its complicated composition. The existence and development of pre-crack result in the complicated strength and strain. The application of fracture mechanics to concrete research greatly promoted the development of concrete fracture mechanics and strength theory. This paper analyzes the reason of crack development mechanism by means of fracture mechanics, and presents an example for research on the temperature crack of concrete surface during temperature drop. Some results show that it is not sufficient to judge cracking of concrete and stability of cracking only by comparison between the temperature stress and the strength of concrete.