| Reinforced concrete structures in areas where the chloride content is rich will often be eroded by chloride salts.The corrosion of steel bars caused by it is an important factor in reducing the service life of reinforced concrete structures.In order to make concrete materials light and strong,and have good resistance to chloride ion erosion,calcium carbonate whiskers are added as an admixture to the ceramsite concrete in this paper.At the same time,considering that the concrete structure in the actual project is corroded by chloride ions under the combined action of temperature and load,the research on the resistance of ceramsite concrete to chloride ions under the combined action of temperature and load has been carried out.The specific research content and results are as follows:(1)Choose three factors and four levels to carry out 64 sets of fully proportioned cement mortar tests.The water-binder ratios are 0.28,0.32,0.36,and 0.40,respectively.The content of calcium carbonate whiskers and fly ash are selected as 0%,5%,10%,and 15%respectively.According to the cement mortar strength test,it is initially obtained that the optimum content of calcium carbonate whiskers is 5%.On this basis,the content of calcium carbonate whisker is selected as 0%,1%,2%,3%,4%,5%,6%,and adding coarse aggregate ceramsite,the concrete mix ratio test was carried out,and finally it was determined that the optimum content of calcium carbonate whiskers in the ceramsite concrete was 5%.In addition,the enhancement mechanism of calcium carbonate whiskers was analyzed from a microscopic point of view in conjunction with electron microscopy experiments.(2)According to different water-gel ratio and calcium carbonate whisker content,three strength grades of ceramsite concrete,LC30(water-gel ratio 0.36,whisker content 0%),LC35(water-gel ratio 0.32,whisker content 0%),LC40(water-gel ratio 0.32,whisker content 5%)are designed.And it used to test the compressive strength and split tensile strength of concrete cubes.The results show that the addition of 5%calcium carbonate whiskers can increase the concrete 28d cube compressive strength and splitting tensile strength by 14%and 9.3%,respectively;it is calculated based on the experiment data that the size conversion coefficient of ceramsite concrete for the size of 100mm×100mm×100mm specimen is 0.9.(3)Through the chloride ion erosion test of the above three strength grades of ceramsite concrete,it is concluded that the relationship between the chloride ion mobility coefficients of the three strength grade test blocks is obtained as LC30>LC35>LC40,adding 5%calcium carbonate whiskers can reduce the penetration depth of chloride ions by 12.1%to 18.3%.And when the water-binder ratio increases from 0.32 to 0.36,the penetration depth of chloride ions increases by 12.95%to 23.41%.Indicating that adding calcium carbonate whiskers can improve the corrosion resistance of concrete to chloride ions,and increasing the water-binder ratio will reduce the corrosion resistance of concrete to chloride ions;as the increase of chloride salt erosion time,the chloride ion mobility and resistivity of the test block gradually decrease.Based on Fick’s first law and Nernst equation combined with electromagnetic field theory,the relationship between the two is obtained and verified by experiments,which has great theoretical and practical significance for the future use of resistivity to study the corrosion degree of chloride in ceramsite concrete.(4)The resistance of ceramsite concrete to chloride ion corrosion under the coupling effect of temperature and load was studied.Based on the Arrhenius formula and the test results,it is concluded that increasing the temperature or increasing the load level can reduce the corrosion resistance of concrete to chloride ions;the COMSOL Multiphysics software was used to simulate the penetration depth of chloride ions in concrete under the coupled effect of temperature and load,and the maximum error between the simulated value and the test value is not more than 1.48%,which provides a reference for future research on the chloride ion erosion of concrete under various environmental effects based on COMSOL software;based on Fick’s second law,a three-dimensional coupling model between chloride ion penetration depth and temperature-load was derived,and three-dimensional surface fitting was performed through Origin.The average R~2of the three strength grade test blocks is 0.93.The established model is in good agreement with the experimental results,and it has an important guiding role for the design and research of the thickness of the steel concrete protective layer of the concrete structure in the area eroded by the chloride salt. |
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