Experimental Study On Uniaxial Compression Stress-strain Relationship Of High Strength Concrete With High Admixture

With the rapid development of urbanization,a large amount of waste materials are emitted while a large amount of resources are consumed.The problem of environmental pollution is becoming more and more serious.Coal-fired power generation and smelting of iron and steel produce large amounts of fly ash and slag powder.If these wastes fail to be properly disposed,they will cause indelible pollution to the environment,and fly ash and slag powder should be used in the construction industry.Not only can the discarded resources be used at the second time,but also play a key role in the protection of the ecological environment.This paper mainly studies the collocation,microcosmic and constitutive relationship of C60 high-strength concrete,which provides some reference for the structural bearing capacity design and finite element analysis.(1)the substitution rate of mineral admixture(fly ash+ slag powder)is up to 50%of the cementitious material.By changing the proportion of fly ash and slag powder and the ratio of water to binder,90 Cube Specimens and 30 prism specimens are tested for mechanical properties.Including compressive strength,flexural strength and splitting tensile test.Determine the ratio of water binder ratio to fly ash and slag powder.The results of mechanical experiments show that C60 high strength concrete can be configured when water binder ratio is 0.24,mixed 10%fly ash and 40%slag powder,and its compressive strength,splitting tensile strength and flexural strength reach 103.49%,93.77%and 97.55%.of reference group concrete respectively.(2)select the best mineral content group and reference group specimens for microscopic characterization analysis,analyze the influence of mineral admixtures on the strength mechanism of concrete,and the best mineral dosage group can see a lot of unhydrated spherical substances in the early stage concrete hydration process from the scanning electron microscope.From the XRD diffraction pattern,it can also be observed that the peak value of C-S-H hydration calcium silicate of reference group is slightly lower than that of mineral content.At the later stage of hydration,a large amount of flocculent gel appears on the outer surface of spherical fly ash,and a large number of "netlike" gel substances appear around it.In the later XRD diagram,the C-S-H diffraction peak increases.The strength of late mineral content group is superior to that of reference group concrete.(3)select the best mineral content and reference group specimens to study the constitutive relationship of concrete,analyze the failure mode of concrete under uniaxial compression.Through the segmental constitutive model of Zhenhai,based on the experimental data and rigorous mathematical deduction,the constitutive relation curve of high volume mineral high-strength concrete under uniaxial compression is better fitted,and the main eigenvalues of the whole curve equation are obtained.It provides a basis for nonlinear analysis of high strength concrete with admixtures.