Experimental Study On Cracking And Fracture Properties Of Self-compacting Concrete

In this paper, the mix design of C35 and C50 grade self-compacting concrete for the complex parts of qin-shan Nuclear Power Plant project was done, then we studied the mechanical properties of the self-compacting concrete we designed.The early age cracking of concrete can lead to concrete deterioration of engineering structures and affect the durability of the structures. In order to improve the durability of engineering, guarantee the long-term quality and safety of concrete structures, it is necessary to ensure the self-compacting concrete have good ability to resist cracking. In this paper, we studied the cracking properties of the self-compacting concrete we designed by free-shrinkage test, slab test and ring test. Then we studied the basic parameter of cracking properties-the flexural ultimate tensile strain of self-compacting concrete we designed by flexural test.Ultimate tensile strain is one of the basic parameters of cracking properties of concrete. It can be studied by tensile test or flexural tensile test.The tensile test is difficult to carry out because of its high requirements of the performance of instruments and the quality of specimen, it can cause stress intensity due to the eccentricity in the course of testing. Comparatively, the flexural strain test is much more easier to carry out and the test results is more stable and reliable compared with the tensile strain test. Besides, there is good relationship between flexural tesile strain and tesile strain. In this paper, the flexural tensile strain test is appled to study the flexural tensile strain of self-compacting concrete.Then we analyzed the cracking properties of self-compacting concrete based on the flexural tensile strain.With the rapid development of design methods for structures, the facture properties of concrete has been paid great concerns, people use it as a parameter to judge the quality of concrete material. The mixture of self-compacting concrete is different from normal concrete, weather it will affect the facture property of concrete needs to be studied.In this paper, we applied three point beam test to study the fracture properties of self-compacting concrete.The three point beam test based on two-parameter model recommended by RILEM has been wildly used in the experimental study of concrete,but it has high demands on the properties of the instruments.In this paper,three point beam test based on double K fracture parameters model was applied to study the fracture properties of self-compacting. But in the three point beam test, we applied the load constantly with time instead of being controlled by displacement, and the crack mouth opening distance was indirectly tested, so the three point beam test can easily be carried out.