中文摘要：

通过微观和宏观观测综合研究不同配比混凝土在干湿循环作用下受硫酸盐侵蚀的劣化规律,设计4个W/C：0.57、0.44、0.35、0.28,对应从普通强度到高强混凝土。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。试验结果表明：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,干状态下又叠加由蒸发作用引起的盐结晶压力的损伤;与普通强度混凝土相比,高强混凝土的W/C小并掺有适量的减水剂,孔隙结构得到优化,使得湿状态下硫酸根传输受阻,干状态下结晶条件遭到一定程度破坏,导致混凝土受侵层厚度明显降低,表现为宏观上的强度劣化程度较轻,表明高强混凝土具有较强的抵抗硫酸盐侵蚀能力。

英文摘要：

The deterioration mechanisms of different mix concretes under sulfate attack in wet-dry cycles were investigated through micro-and macro-observations. Four W/C ratios,0.57,0.44,0.35 and 0.28,were employed,corresponding to ordinary to high strength concrete. Micro-observations included analysis of the products using thermal analysis and determination of the sulfate-ion content profile using the modified barium sulfate gravimetric method （chemical titration method）. Macro-observations mainly included the mechanical behaviors such as compressive strength and splitting strength. Test results indicated that in wet-dry cycles,the concrete was attacked by expansive products such as ettringite and gypsum during the wetting cycle,and salt crystallization damage,induced by evaporation,is superposed during the drying cycle. Comparing with ordinary strength concrete,the W/C ratio for high strength concrete is small,and proper amount of water reducing admixture is added to refine the pore structure and thus block the transport of sulfate ions during the wetting cycle and reduce crystallization during the drying cycle,so that the thickness of layer under the attack is decreased significantly,and as a result,the degradation of macro-strength is effectively reduced. All of these indicated that high strength concrete can better resist sulfate attack.