Study On Salt Erosion Damage Of Papermaking White Mud Ceramsite Concrete

The paper summarizes the research progress on the material properties and application of papermaking white mud,as well as the corrosion mechanism of concrete by chloride,sulfate,chloride-sulfate coupling,and so on.The purpose of this paper is to use white mud as an admixture in the reasonable use of fly ash ceramsite concrete.According to the salt erosion environment of the sulfate and chloride salts in coastal and salt-rich areas,the mixing ratio,mechanical properties and salt erosion resistance of ceramsite concrete mixed with papermaking white mud were studied.The analysis of its early deterioration and damage law and mechanism under salt erosion environment provides an important basis for whether papermaking white mud can be used in fly ash ceramsite concrete.The research content of this thesis includes the following aspects:(1)This article designed a four-factor mixed orthogonal test with water-binder ratio(4 levels),white mud content(8 levels),fly ash content(4 levels),and silica fume content(4 levels).The cubic compressive strength was used as the main evaluation index,and the influence degree of each factor was analyzed by the visual analysis method and the analysis of variance method.Determined the proportion of two groups for subsequent salt erosion resistance tests: 1 group with optimal ratio(water-gel ratio 0.33,white mud 3%,fly ash 0%,silica fume 9%)and optimal control blank control group(water-gel ratio 0.33,white mud 0%,pulverized coal Ash 0%,silica fume 0%).(2)Measure the mechanical properties of fly ash ceramsite concrete in the above two groups,including cubic compressive strength,split tensile strength,axial compressive strength,and static elastic modulus at different ages,and get the stressstrain relationship of concrete during the process.Compared with the blank control group,the compressive strength of the cubes in the optimal group increased from 9.44% to 19.80% after 28 days;the split tensile strength increased by 14.1%;and the axial compressive strength increased by 6.63%.The static elastic modulus decreases by 7.10%,and the stiffness decreases.Based on the electron microscope image,the reason for the increase in the intensity of the optimal group was analyzed.(3)Investigate the effects of chloride and sulfate concentrations on fly ash ceramsite concrete under the soaking mechanism and the effect of dry and wet cycles on the process of salt erosion were studied through indicators such as cube compressive strength,mass,relative dynamic elastic modulus,chloride ion mobility coefficient,and chloride ion concentration at different depths of the concrete.In a certain range,the higher the salt concentration is,the higher the corrosion rate is.After the salt concentration exceeds the range,the corrosion rate is similar.The dry and wet cycle can inhibit the chloride salt erosion and promote the sulfate erosion.(4)Compare the difference of chlorine and sulfate resistance of fly ash ceramsite concrete in the two groups.At the age of 7 days,the chloride transfer coefficient of the optimal group was lower than that of the blank control group by 20.5%;at 88 days,the chloride transfer coefficient of the optimal group was lower than the control group by 72.3%.Within 0d ~ 60 d of sulfate + wet and dry cycle,the relative dynamic elastic modulus of the optimal group was 0.001 ~ 0.011 higher than that of the control group.The experiments show that the optimal group with white mud and silica fume has better salt erosion resistance than the control group.(5)Based on Fick's first law and Fick's second law,the diffusion model of chloride ions in concrete was derived,and the relationship between free chloride ion concentration and time at different depths of concrete was obtained and verified.