Experimental Study On Early Autogenous Shrinkage Performance Of C60 Concrete Under Different Constraints

The steel plate-concrete composite shear wall structural system has already become a main load-bearing structure in super high-rise buildings in China because of its high load-bearing capacity and low space occupancy.However,under the interaction of initial defects,curing conditions and boundary constraints,it is prone to early non-load cracking,reducing the structural bearing capacity,seismic performance,and durability.The nonload cracking is mostly caused by the restrained shrinkage deformation of high-strength concrete.Therefore,the research and analysis of the factors and rules affecting the shrinkage of high-strength concrete is the core issue of solving the problem of the safe service of the steel plate-concrete composite shear wall.Based on the shrinkage characteristics of concrete,this paper deduces the theoretical calculation model for the stress and strain of concrete specimens under different constraint conditions according to the compatibility deformation and plane-section assumption.Combined with engineering practice,specimens and molds that simulate an actual constrained state are designed,and the internal and external constraints,reinforcement ratio,steel plate spacing,configuration mode,and the differences between steel plates and steel bars are set as test variables,while a plain concrete control group is set up and designed.The C60 concrete shrinkage series test systematically analyzes the effect of different constraints on the autogenous-shrinkage behavior of C60 concrete,and the main conclusions including:(1)The restraining ability of the restraint on the concrete is inversely related to the distance between the two.It has strong restraining effect on the concrete with a short distance and a weak restraining effect on the concrete with a long distance.(2)Under the condition of the same steel ratio,concentrated distribution of steel plates or separate distribution of steel plates with excessive distances will cause serious uneven distribution of concrete.(3)In external restraint specimens,the distribution of steel plates can greatly reduce the lateral pull force generated by the self-shrinkage of concrete in the adjacent structure,and the weakened effect of the separate steel plate on the lateral pull force is more obvious.