Experimental Study On The Strength Of Wet-screened Large Aggregate Concrete Under Multiaxial Loads After Freeze-thaw Cycles

Freeze-thaw resistance is used as a key to measure the durability of concrete.Presently, most experimental and theoretical studies are focused on the relative dynamic modulus of elasticity,weight loss.The experiments about mass concrete after freeze-thaw cycles are fewer at home and abroad.So,based on the project of National Nature Science Foundation named " multiaxial strength and failure criterion in octahedral stress space of mass concrete in freeze-thaw environments "(50679007),the experimental researches and theory studies on weight loss of wet-screened large aggregate concrete specimens and three degree of large aggregate concrete specimens after different freeze-thaw cycles,and the uniaxial and biaxial strength of wet-screened large aggregate concrete specimens after different freeze-thaw cycles are carried out.Main research contents in this paper are listed as follows:1.Freeze-thaw cycling experiments of wet-screened large aggregate concrete specimens (100mm×100mm×100mm) and three degree of large aggregate concrete specimens(250mm×250mm×250mm) have been carried out.The freeze-thaw cycles include 50,100,150,200,250,300.After different freeze-thaw cycles,the surface forms of both concrete are compared and analyzed.The weight loss is measured on each frost-resistance grade of 50 times of freeze-thaw cycles.2.Uniaxial compression and tension loading experiments of wet-screened large 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 established.3.The experimental study on strength of wet-screened large aggregate concrete under biaxial compression after different cycles of freeze-thaw was performed.The failure modes were observed.The influences of freeze-thaw cycles and stress ratio on the ultimate compressive strength were analyzed.In addition,the failure criterion of wet-screened large aggregate concrete under biaxial compression with consideration of the influence of freeze-thaw cycles and stress ratio was proposed.4.The experimental study on strength of wet-screened large aggregate concrete under biaxial tension-compression(T-C) after different cycles of freeze-thaw was performed.The failure modes were observed.The influences of freeze-thaw cycles and stress ratio on the ultimate compressive and tensile strength were analyzed.The failure criterion under biaxial tension-compression is proposed expressed in terms of principal stress.In addition,the failure criterion of wet-screened large aggregate concrete under biaxial tension-compression with consideration of the influence of freeze-thaw cycles and stress ratio was established in octahedral stress space.