Preparation And Properties Of Green Steel Slag UHPC

The application of steel slag powder in UHPC can not only effectively improve the utilization rate of steel slag,but also reduce its pollution to the natural environment.This paper focuses on the effect of steel slag powder replacing cement in UHPC.UHPC is prepared by using steel slag powder with different substitution rates instead of cement.The effects of steel slag powder substitution rate and water-binder ratio on the working properties,mechanical properties and microstructure of UHPC were studied.The bending property test of UHPC beam and the environmental impact calculation of steel slag UHPC were carried out to study the application of steel slag UHPC.The specific research results are as follows:(1)By testing the macroscopic properties of UHPC with different substitution rate of steel slag powder and different water-binder ratio,such as fluidity,flexural strength and compressive strength,to explore the influence of steel slag powder substitution rate and water-binder ratio on these macroscopic properties.The test results show that the fluidity of UHPC will increase with the increase of steel slag powder substitution rate.The addition of steel slag powder will significantly affect the flexural strength and compressive strength of UHPC.When the substitution rate is not more than 25%,the compressive strength loss of UHPC is within a reasonable range,and the substitution rate is not more than 10%,the flexural strength loss of UHPC is within a reasonable range.The fluidity of UHPC will increase with the increase of water-binder ratio.The water-binder ratio will significantly affect the flexural strength and compressive strength of UHPC,and the flexural strength and compressive strength of UHPC will decrease with the increase of water-binder ratio.(2)The microscopic properties of UHPC with different substitution rate of steel slag powder and different water-binder ratio were investigated by electron microscope scanning(SEM),X-ray diffraction(XRD)and comprehensive thermal analysis(TG-DSC).The SEM test results show that the UHPC with low water binder ratio has a better dense slurry structure,and the amount of hydration products decreases with the increase of steel slag powder substitution rate.Through the XRD test,it is found that there are obvious C2 S and C3 S diffraction peaks in the UHPC with low water-binder ratio,and there are obvious diffraction peaks of Gismondine in all the experimental groups.Through TG-DSC analysis,it is found that the change of water-binder ratio will not affect the final heat absorption of UHPC,but will affect the mass loss of UHPC to a certain extent.With the increase of the substitution rate of steel slag powder,the mass loss of UHPC is basically the same,but the degree of heat absorption of UHPC will increase.(3)Through the bending performance test of six steel slag UHPC beams,the effects of steel slag powder substitution rate and water-binder ratio on the bending performance of UHPC beams were studied.The test results show that the steel slag powder substitution rate and water binder ratio can affect the bending performance of UHPC beams to a certain extent.With the gradual increase of steel slag powder substitution rate and water-binder ratio,the bending performance of UHPC will decline to a certain extent,and the addition of steel slag powder will make UHPC crack earlier to a certain extent.(4)Through the calculation and analysis of the environmental impact of steel slag UHPC,it is found that the addition of steel slag powder can greatly reduce the environmental impact problems such as resource consumption,energy consumption and CO2 emission of UHPC in the production stage.