Experimental Study On Behavior Of Recycled Concrete Under Combined Compressive Andshearing Stresses

First of all,basing on the 18 cube specimens and 9 group prism specimens for basic mechanical test and direct shear test by true triaxial testing machine,compared to the damage form of recycled concrete and ordinary concrete,study on the effect of substitution rate and water ash ratio on the direct shear strength of regenerative concrete.Experimental results show that the recycled concrete direct shear strength decreases with increasing replacement ratio,and decreases with increasing water cement ratio,but the relationship between the specific value of recycled concrete direct shear strength and compressive strength and the recycled coarse aggregate replacement ratio is not obvious,suggesting?= 0.095fcu.Secondly,basing on the study of the pressure of 12 groups of cube specimens cut compound stress test,compared to the damage form of recycled concrete,discussed the relationship between limit shear stress and shear strain limit and replace rate and the the normal compressive stress.Experimental results show that the recycled concrete compression-shear failure pattern is similar to normal concrete,recycled concrete spalling is more obvious than ordinary concrete spalling when damaged,increasing with the normal compressive stress of specimen damage occurs more inclined cracks,but finally is sheared opening along the central;The limit shear stress of recycled concrete increases with the increase of the compressive stress,the ratio of the limit shear stress of the recycled concrete and compressive strength decreases with the increment of replacement ratio;The recycled concrete limit shear strain increase with normal compressive stress and the place of rate when the concrete damaged.Established the shear stress and shear strain constitutive model,and proposed the recycled concrete pressure-cut compound stress strength criterion combining octahedral strength criterion.Finally,basing on the study of the pressure of 45 groups of reinforced concrete specimens cut compound stress test,compared with reinforced concrete compression-shear composite stress failure pattern,explored the ultimate shear stress and the steel pin plug and shear slip and normal compressive stress and reinforcement ratio and replacement ratio,analysised the relationship between load and steel bar strain curve.Experimental results show that ratio of the limited shear stress and the compressive strength of the reinforced concrete specimen with recycled coarse aggregate decreases with the increase of replace rate;Steel bolt pin effect decreases with the increase of replacement ratio,stress steel bolt pin function is less and less obvious along with the increase of the normal compressive.Established the pre-splitting reinforced concrete direct shear calculation method of the limiting shear stress and pressure cut the calculation method of the limit of the shear stress under the above-mentioned complex mechanical state.