H_(2)C_(2)O_(4)侵蚀下混凝土性能的劣化研究

Research on the degradation of concrete performance under H_(2)C_(2)O_(4)erosion

目的:研究草酸侵蚀下混凝土物理力学性能及微观结构的劣化趋势,探索草酸作为混凝土锈斑清除剂的合理浓度范围。方法:采用2.5%、5%、7.5%、10%、12.5%浓度的草酸,对C20~C45混凝土浸泡4、6、8、10 h后,测试混凝土强度、孔结构、氯离子渗透能力及其水化产物的变化,计算混凝土的退化深度。结果:随着草酸浓度的提高,浸泡后混凝土强度呈下降趋势,混凝土退化深度增大,混凝土中大孔数量增多,毛细孔数量降低,电通量增大;混凝土强度越高,草酸对混凝土性能劣化程度降低;在相同浓度的草酸溶液浸泡4~10 h的混凝土,混凝土性能变化差别不大。结论:混凝土在2.5%、5%、7.5%、10%、12.5%的草酸溶液中浸泡4~10 h以内时,浸泡时间对混凝土性能影响较小,草酸浓度对混凝土性能影响较大。在2.5%浓度的草酸溶液浸泡下,C20~C30混凝土强度下降达到10%;强度等级大于C30的混凝土,5%浓度的草酸溶液浸泡后,强度下降率不超过5%。用草酸清洗混凝土时,草酸溶液的浓度不宜大于2.5%。

Object:Studying the degradation trend of physical and mechanical properties and microstructure of concrete under oxalic acid erosion to explore the reasonable concentration range of oxalic acid as a concrete rust spot remover.Methods:Concretes with different strength grades(C20~C45)was soaked in a gradient concentration solution of oxalic acid(ρ=2.5%,5%,7.5%,10%,12.5%)for 4,6,8,10 h.Strength,pore structure,chloride ion permeability and changes in hydration products were tested to calculate the degradation depth of the concrete.Results:With the increase of oxalic acid concentration,the strength of concrete after being soaked showed a downward trend,the depth of concrete degradation increased,the number of large pores in the concrete increased,the number of capillary pores decreased,and the electric flux increased.In addition,the higher the strength of concrete,the less effect of oxalic acid on concrete performance.For the effect of erosion time on concrete properties,concrete performance has little difference after being soaked from 4 h to 10 h in the same concentration of oxalic acid solution.Conclusion:Within 4 h to 10 h of immersion,the erosion time has little effect on the performance of concrete,but the concentration of oxalic acid has a greater effect on the performance.Concrete with strength grades from C20 to C30 will drop by 10%of strength after being soaked in 2.5%oxalic acid solution.For concrete with strength grades exceed C30,the strength drop will not exceed 5%after being soaking in 5%oxalic acid solution.When oxalic acid is used to clean concrete,the concentration of oxalic acid solution should not be over 2.5%.