Study On Mechanical Properties Of Recycled Large Aggregate Self-Compacting Concrete

Recycled large aggregate self-compacting concrete is a new type of concrete material that uses recycled concrete blocks and bricks as the large aggregate and uses rock-filled concrete construction technology as the main construction method.Not only has the construction efficiency of large-volume concrete been greatly improved,but also construction waste such as waste concrete blocks can be effectively used,which has created good technical and social benefits for green building technology.This paper takes the recycled large aggregate self-compacting concrete as the research object,and uses the experimental method to study the mechanical properties of the recycled large aggregate self-compacting concrete.The cubic compressive strength test,cubic split tensile strength test,prism axial compressive strength test and axial compressive damage test of recycled large aggregate self-compacting concrete were carried out respectively.According to the test results,the axial compressive strength and elastic modulus of different members are obtained,and the failure mode of the axial members under compression is obtained.The stress-strain curve of the recycled large aggregate self-compacting concrete under uniaxial compression is obtained,and the regeneration is analyzed and obtained.Constitutive model of stress and strain of self-compacting concrete with large aggregates under uniaxial compression.In addition,the ultrasonic detection method was used to test the damage of self-compacting concrete with recycled large aggregates under uniaxial compression,and the damage characteristics of self-compacting concrete with recycled large aggregates during compression were analyzed.The main conclusions are:1)Cube compressive strength test results of recycled large aggregate self-compacting concrete show.The compressive failure pattern of the recycled large aggregate self-compacting concrete cube test block is basically the same as that of ordinary concrete.The cubic compressive strength of the recycled large aggregate self-compacting concrete increases with the increase of the aggregate particle size,the strength level of the recycled aggregate,and the strength level of the self-compacting concrete.As the aggregate particle size,the strength grade of the recycled large aggregate,and the strength grade of the self-compacting concrete increase,the split tensile strength of the recycled large aggregate self-compacting concrete increases.As the compressive strength of the cube increases,the splitting tensile strength of the recycled large aggregate self-compacting concrete increases.2)The axial compression failure of the self-compacting concrete of the recycled large aggregate is carried out from the initial cracks,and eventually a plurality of vertical or oblique cracks are formed.As the concrete on the surface of the test block falls off,the final test piece is damaged.Losing capacity.The failure mode is basically the longitudinal and oblique cracks.The axial compressive strength of the recycled large aggregate self-compacting concreteincreases with the increase in the particle size of the recycled aggregate,the strength level of the self-compacting concrete,and the strength of the recycled aggregate.3)The stress-strain curve of self-compacting concrete prisms with recycled large aggregates under axial compression is initially straight,and the stress-strain curve is basically a straight line;when the stress reaches 80% to 100% of the ultimate strength,the slope of the stress-strain curve begins to decrease,Plastic deformation began to occur.When the peak stress is reached,the curve is close to the horizontal section,and the horizontal section of most components is small or almost inconspicuous.As the load reaches its peak stress,the component fails.Fit the stress-strain curves of each group of components of the self-compacting concrete prismatic column of the recycled large aggregate under axial compression.The cubic polynomial curve based on the Zhenhai formula and the trigonometric function curve based on the Young formula are compared with the actual measurement The obtained stress-strain relationship is in a high degree of agreement,while the rational curve fitted based on the CEB-FIP formula and the exponential curve fitted based on the Sahlin formula are slightly lower than the measured values,which are somewhat conservative,but all of them agree Claim.4)The damage variable D of self-compacting concrete and ordinary concrete of recycled large aggregates increases with the increase of deformation.The damage variable D decreases with the increase of recycled aggregate particle size,recycled aggregate strength and self-compacting concrete strength.Among them,the strength of the self-compacting concrete has the most significant influence on the damage variable D of the self-compacting concrete with recycled large aggregate.The damage variable D of the recycled large aggregate self-compacting concrete at the initial loading is very small;when the strain reaches about20% of the peak strain,the specimen begins to have damage.As the load is further increased,tiny cracks are generated on the surface of the test piece,and the cracking direction of the crack is along the direction of the principal stress,and the test piece begins to damage;thereafter,as the load gradually increases,the damage value continues to increase,The curvature of the damage curve is very small.Finally,when the strength of the test piece is close to the peak stress,the curvature of the damage curve gradually increases,the damage rate of the component begins to accelerate,the cracks on the surface of the component begin to penetrate,and eventually damage occurs.The damage value at the time of destruction is about 0.27 ~ 0.35.