硫酸盐介质腐蚀混凝土灌注桩的质量与强度演变

Evolution of Mass and Strength of Concrete Cast-in-situ Piles Under Sulfate Medium Attack

摘要:

为模拟混凝土灌注桩在硫酸盐渍土环境中侵蚀劣化规律，开展了现浇混凝土试件硫酸盐侵蚀试验，并研究了现浇混凝土试件硫酸盐侵蚀劣化机制.与预制混凝土试件劣化机制进行对比，分析现浇混凝土试件与预制混凝土试件硫酸盐侵蚀劣化的异同.分析水灰比、硫酸盐溶液浓度对现浇混凝土试件耐久性的影响，通过质量变化率、抗压强度相对值分析现浇混凝土试件劣化规律.结果表明：混凝土质量和抗压强度均呈现先增加后减少的趋势；同一条件下，现浇混凝土试件最先出现了质量和强度损失，损失率分别为0.4%和15%；硫酸盐溶液浓度的增加对现浇混凝土试件劣化规律不明显，而混凝土水灰比越大，现浇混凝土试件更易趋于劣化.

关键词:混凝土灌注桩;硫酸盐侵蚀;抗压强度;质量损失

Abstract:

To simulate the degradation of cast-in-situ piles exposed to sulfate saline soil environments, a corrosion experiment of cast-in-situ specimen was conducted. The deterioration mechanism of fresh concrete specimen was studied. The difference of deterioration mechanism between precast concrete specimen and fresh concrete specimen was analyzed with comparison experiments. The effect of watercement ratio and concentration of sulfate solution on the durability of cast-in-situ concrete specimen was analyzed. The mass change rate and the relative value of compressive strength were used to quantify the degradation rule of fresh concrete specimen. The results show that both the concrete mass and the compressive strength increases firstly and then decreases. In the same condition, the fresh concrete specimen is the first to show the mass and compressive strength loss. The loss rate is 0.4% and 15%, respectively. The increase of sulfate concentration has not obvious effect on the degradation law of the fresh concrete specimen. However, with the watercement ratio increases, the fresh concrete specimen is prone to deterioration.

Key words:cast-in-situ pile; external sulfate attack; compressive strength; mass loss