Study On The Strength Of Wet-screened Aggregate Concrete Under Multiaxial Stress States After Freeze-thaw Cycles In Seawater

Experimental study on multiaxial failure criterion of concrete before and after wet-screened is just at the initial stages. Presently, there are quite few researches in this field, and most of them are focused on the normal and uniaxial stress conditions. The experiments about the wet-screened aggregate concrete after freeze-thaw cycles are fewer. As a part of the project of National Nature Science Foundation named "multiaxial strength and octahedron stress space failure criterion of large aggregate concrete"(50479059), experimental researches and theory studies on weight loss, the ultrasonic speed, the splitting-tensile, uniaxial compression and biaxial compression strength of two graded aggregate concrete and wet-screened aggregate concrete after different freeze-thaw cycles are carried out. Main research contents in this paper are listed as follows:(1) Freeze-thaw cycling experiments of two graded aggregate concrete (150mm×150mm×150mm) and wet-screened aggregate concrete (100mm×100mm×100mm) specimens have been carried out. The freeze-thaw cycles include 50, 100, 150, 200, 250. The weight loss and the ultrasonic speed are measured on each frost-resistance grades.(2) The splitting-tensile experiments have been carried out on the concrete specimens before and after wet-screened under normal environment and after different freeze-thaw cycles. The failure patterns of concrete are described. Relationship between the decreasing percents of strength of concrete and the freeze-thaw cycles is analyzed. Then, formulae with describe the relationships between the strength of concrete and freeze-thaw cycles, primary graded aggregate concrete and wet-screened aggregate concrete are established.(3) Uniaxial loading experiments of primary graded aggregate concrete and wet-screened aggregate concrete specimens under normal environment and after freeze-thaw cycles have been carried out with triaxial test system. The failure patterns of concrete are described. Relationship between the decreasing percents of strength and the freeze-thaw cycles is analyzed. Then, formulae with describe the relationships between the strength of concrete and freeze-thaw cycles, primary graded aggregate concrete and wet-screened aggregate concrete are established.(4) Biaxial compression experiments with equal proportion loadings are carried out on two kinds of concrete specimens under normal environment and after freeze-thaw cycles. The results are brought out with the descriptions of the failure patterns of concrete together with...