混凝土受不同浓度水平硫酸盐侵蚀劣化机理试验研究

本文通过微观和宏观观测综合揭示了干湿循环作用下混凝土受不同浓度水平硫酸盐侵蚀的劣化规律，微观观测包括用热分析方法进行侵蚀产物分析和用改进硫酸钡重量法（化学滴定法）测量由表及里不同深度处硫酸根含量，宏观观测主要包括抗压强度、劈裂抗拉强度等基本力学性能。干湿循环作用下，湿状态下混凝土受到钙矾石、石膏等膨胀性侵蚀产物的作用，干状态下又叠加Na2SO4.10H2O结晶压力的损伤。当侵蚀溶液浓度比较高时，湿状态下硫酸根更容易扩散进入混凝土内部，干状态下生成的Na2SO4.10H2O晶体数量多，导致混凝土受侵层厚度比较大，表现为宏观上的强度劣化程度就严重。研究成果可为进行干湿循环作用下混凝土硫酸盐侵蚀的评估和预防提供依据。

Experiment Study on Deterioration Mechanism of Concrete Suffered From Different Concentration Levels of Sulfate Attack

By micro- and macro-observations, this paper reveals the deterioration mechanism of concrete suffered from different concentration levels of sulfate attack under action of wet-dry cycles. Micro-observations include the analysis of attacking products by thermal analysis method and the determination of sulfate-ion content from surface to inside by modified barium sulfate gravimetric method (chemical titrating method). Macro-observations mainly include the mechanical behaviors such as compressive strength, splitting strength. Under action of wet-dry cycles, concrete is attacked by the expansile attacking products such as ettringite, gypsum during the wetting condition, and then crystallization damage induced by Na2SO4.10H2O is superposed during the drying condition. When the concentration of the attacking solution is high, during the wetting condition sulfate-ions are much easier to diffuse into the inside of concrete, and the amount of Na2SO4.10H2O generated during the drying condition is large, which result in the large thickness of the attacked layer, and as a result, the degradation of macro-strength such as compressive strength, splitting strength is serious. These researches can provide references for the assessment and prevention to sulfate attack on concrete under action of wet-dry cycles.