Research On Crack Control In Cast-in-place Floor Slabs Based On The Experiment And Numerical Simulation For Concrete Drying Shrinkage

The crack of reinforced concrete cast-in-situ slab has always been concerned by the investment units, the construction units and vast residents of owners. And it has direct effects on the integral image of construction. It therefore has a certain social and economic significance for the study of causes of crack and its control measures.The drying shrinkage of concrete is a crucial factor of forming none-bearing cracks. This paper explores the regularity of drying shrinkage of concrete based on the experimental data and numerical simulation. And presents some crack control measures which can be used as the reference for engineering practice in the aspects of design, construction and materials. The main contents of paper are as follows:(1) The experiment designs and makes 70 concrete specimen, and cures them in a special drying shrinkage laboratory, then measures their shrinkage strain and compressive strength at the age of 0~120 days.(2) This paper explores the regularity of shrinkage of concrete according to the experimental results, clarifies the influence of high volume of coal ash, different watercement ratio, different kinds of coal ash and admixture dosage on shrinkage and compressive strength of concrete. It also optimizes the mix proportion based on the experiment, minimizes the shrinkage and maintains its mechanical property at the same time.(3) It presents a drying shrinkage prediction model which fits the concrete with coal ash admixture on the basis of comparing and analyzing several typical drying shrinkage prediction models both domestic and overseas, and verifies its accuracy and proportionality.(4) It solves the humidity field in the way of solving temperature field adapting ANSYS thermal analysis modules, and conducts a coupling analysis for the humidity field and strain field, simulating the drying shrinkage of concrete, and verifies the feasibility of numerical simulation by comparing the calculated results with the experimental results.(5) It simulates the drying shrinkage process of cast-in-situ concrete slab using the above method, concludes the influence of the strength grade of concrete, thickness of slab, environmental humidity, boundary constraint and reinforcement ratio on the principal stress distribution, and proposes some control measures based on the above analysis.