The Mechanical Analysis And Control On Shrinkage Cracking For Concrete Structure

The shrinkage cracking of concrete is an important problem in the academic circles and structure engineering. From the point of restraint for the shrinkage cracking, the experimental and theoretic studies are further conducted on the three basic factors (the shrinkage strains of concrete, the mechanical properties of concrete, and the degree of restraint for concrete). So, the mechanism of the shrinkage cracking is deeply studied, and the effective control measures of the shrinkage cracking for concrete structure are supposed to reply the need of the engineering.1. The drying shrinkage strains of 28 plain concrete test specimens are measured on series 360 days. The main factors (the age, the compressive strength, the environmental condition and the dimension of specimen) of shrinkage for concrete are analyzed in detail. From the point of applicability, the 28-day compressive strength for concrete is regarded as a comprehensive variable, the changes of temperature and relative humidity are all considered in the environmental condition, and the theoretic thickness of specimen is also considered. Based on 67 experimental strains, considering the influence of the concrete age and the compressive strength, the basic formula of free drying shrinkage for concrete is gained under standard condition by aggression analysis; Based on the basic formula of free drying shrinkage for concrete, the multi-coefficient formula of free drying shrinkage for concrete under non-standard condition is gained by multi-coefficient superposition method. In the formula, the temperature-relative humidity coefficient and the dimension coefficient are all considered. The calculation strains of the multi-coefficient formula are well identical with the 130 experimental strains. The above coefficients in the formula are simply, and change continually.