Effect Analysis Of Silica Fume Modified Ordinary Concrete And Self-compacting Concrete

With the implementation of our government’s double control policies on total energy consumption and energy consumption intensity,the limited production of the cement industry is aggravated,leading to rising prices.At the same time,the industrial solid waste silica fume has excess capacity,the price is constantly falling,and most of the silica fume with medium and low silica content has not been developed and utilized.Silica fume directly discharged into the air or directly stored will cause harm to the environment and human health.Therefore,the resource utilization of industrial solid waste silica fume is of great significance for environmental protection and engineering application.If silica fume can be used in concrete admixture,it will not only reduce the cost of concrete,but also reduce the carbon emissions produced by cement production.Therefore,this thesis chooses to analyze the effect of silica fume-modified ordinary concrete and selfcompacting concrete as the topic.By studying that silica fume can replace fly ash and cement paste with equal mass and replace cement with a different mass ratio under different dosages,Its influence on the working performance of fresh concrete,as well as mechanical properties,hydration process,pore structure,and microstructure characteristics of ordinary concrete and self-compacting concrete was studied.To explore the feasibility of the application of silica fume in concrete,to achieve a larger scale of solid waste silica fume resource application,so that the concrete industry to sustainable development.The main conclusions are as follows:(1)With the increase of silica fume replacing fly ash,the slump of ordinary concrete mixture gradually decreased,and the gas content showed a trend of decreasing first and then increasing.The compressive strength of concrete at each age showed a trend of first increasing,then decreasing and then increasing with the increase of silica fume content.When the replacement amount of silica fume was 50%,the microstructure of concrete was the densest,and the compressive strength of concrete at each age was improved the best,which was the optimal mix ratio.With the increase of silica fume content,the total water content in hardened concrete showed a general trend of gradual increase.The cubic compressive strength of the concrete was inversely proportional to the total water content,adsorption water content,and pore water content in concrete,and proportional to the free water content.(2)With the increase of silica fume instead of cement paste,the slump and gas content of the concrete mixture would gradually decrease.When the amount of silica fume substitution increased from 0% to 10%,the cubic compressive strength of the concrete using silica fume(SF)increased by 26.7%,and the splitting tensile strength increased by40.7%,while the cost per cubic meter of concrete increased by only 1.9%.Concrete using high-purity silica fume(HSF)increased their compressive strength by 44.7% and their splitting tensile strength by 57.4%,while the cost per cubic meter of concrete increased by only 5.3%.The total porosity of concrete decreased gradually with the increase of silica fume substitution,in which the proportion of macropores(>10μm)decreased gradually,while the proportion of mesopores(0.1-10μm)and capillary pores(0-0.1μm)increased gradually,which significantly refined the pore structure and made the microstructure more compact.(3)With the increase of the mass ratio of silica fume instead of cement,the fluidity of the self-compacted concrete mixture gradually increased,and the gas content first decreased and then increased,while the drying shrinkage rate at the age of 3d first increased and then decreased.The cubic compressive strength and splitting tensile strength of concrete showed a trend of increasing first and then decreasing,while the total porosity of concrete showed a trend of decreasing first and then increasing.When the mass ratio of SF and HSF replacing cement was 1:2,the mechanical properties of concrete were improved most significantly,and the cost of concrete per cubic meter was also significantly reduced.