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新拌混凝土抗硫酸盐腐蚀试验研究

Experimental Research of Sulfate Corrosion Resistance of Fresh Concrete

【作者】 董庆友

【导师】 张敬书;

【作者基本信息】 兰州大学 , 防灾减灾工程及防护工程, 2013, 硕士

【摘要】 本文主要研究了新拌混凝土在硫酸盐腐蚀环境下的耐久性能。考虑Na2S04和MgS04两种腐蚀介质,Na2S04溶液的浓度5000mg/L和50000mg/L,MgS04溶液的浓度4225mg/L和42250mg/L;采用全浸泡的试验方法模拟混凝土所处的实际腐蚀环境,测定了粉煤灰掺量为0%、15%、20%、25%、30%和35%的混凝土试块在腐蚀龄期30天、90天、180天、270天和360天时的抗压强度、回弹值及质量。以抗压强度耐蚀系数作为主要的评价指标,辅以回弹值和质量变化率,并对部分混凝土试块做SEM扫描和XRD衍射技术分析,从宏观和微观两个层面上分析了新拌混凝土的抗硫酸盐腐蚀性能。研究结果表明,在360天试验龄期内,新拌混凝土比预制混凝土的抗硫酸盐腐蚀性能好。无论是新拌混凝土还是预制混凝土,掺入粉煤灰有利于提高其抗硫酸盐腐蚀能力,试验研究表明在硫酸钠或硫酸镁溶液中混凝土粉煤灰的最佳掺量为25%。对混凝土回弹值进行回归分析得到了预制混凝土和新拌混凝土受硫酸盐腐蚀后的专用测强曲线回归方程,利用该方程推算的抗压强度与试验值发展趋势吻合较好,能够较好的预测混凝土的抗压强度。在全浸泡的腐蚀环境下,无论是新拌混凝土还是预制混凝土,腐蚀介质浓度越高对混凝土的腐蚀程度就越严重;不同腐蚀介质对混凝土的抗硫酸盐腐蚀能力的影响并不相同。在硫酸钠腐蚀环境中,混凝土在极端恶劣腐蚀环境比在普通腐蚀环境中的腐蚀程度严重;在硫酸镁溶液中,混凝土在极端恶劣环境和普通腐蚀环境中的抗腐蚀能力与粉煤灰掺量有关。建立了混凝土受腐蚀时的抗压强度计算模型并提出劣化阶段的抗压强度耐蚀系数的修正计算公式,理论计算结果与试验值吻合较好,能够较好的预测受腐蚀混凝土在劣化阶段的抗压强度耐蚀系数退化规律。

【Abstract】 The durable performance of fresh concrete under sulfate corrosion environment was studied. Two kinds of corrosive medium, Na2SO4and MgSO4, were considered. The solution concentration of Na2SO4is5000mg/L and50000mg/L, and the solution concentration of MgSO4is4225mg/L and42250mg/L. Specimens were completely immersed in sulfate solution which was aimed at simulating the real corrosion environment. The compressive strength, rebound value and mass of concrete specimens in different corrosion ages (30d,90d,180d,270d and360d) were measured corresponding to different mixing percentage (0%,15%,20%,25%,30%and35%) of fly ash. The evaluation index is corrosion resistance coefficient of compressive strength, rebound value and mass-change rate. Some of concrete specimens were analyzed by using SEM and XRD technology. The sulfate corrosion resistance of fresh concrete was analyzed at both macro level and micro level.The results indicate that the sulfate corrosion resistance of fresh concrete is better than that of precast concrete within the experimental period of360days. The sulfate corrosion resistance can be improved by mixing with a certain amount of fly ash both for fresh concrete and precast concrete. The experimental research indicates that the optimal mixing amount of fly ash is25%for specimens immersed in magnesium sulfate or sodium sulfate solution. A regression equation was proposed to predict the compressive strength of fresh concrete and precast concrete corroded by sulfate on the base of rebound values of specimens. The development tendency of calculated compressive strengths agree well with experimental values.For fresh concrete and precast concrete both fully immersed in corrosive solution, the higher the corrosion medium concentration, the more serious the corrosion extent of concrete will be. The influence on the sulfate corrosion resistance of concrete by different corrosion medium is various, which is related to the concentration of corrosive medium. In sodium sulfate solution, the corrosion extent of concrete in the extreme corrosion environment is more serious than that in the general corrosion environment. In magnesium sulfate solution, the sulfate corrosion resistance of concrete in the extreme and general corrosion environment is both related to the amount of fly ash. A calculation model of the compressive strength for corroded concrete is created and a modified formula of corrosion resistant coefficient of compressive strength in degradation stages is proposed. The theoretical calculation results are in good agreement with the experimental values which indicates that the proposed modified formula can predict the degradation law of corrosion resistant coefficient of compressive strength of corroded concrete in degradation stages.

  • 【网络出版投稿人】 兰州大学
  • 【网络出版年期】2013年 11期
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