Resistance against Sulfate Erosion of Concrete Partition under High Temperature and Dry-Wet Cycle
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摘要:
针对海洋工程中混凝土材料在硫酸盐环境中的损伤劣化问题，开展在半浸泡环境中不同浓度的硫酸盐溶液侵蚀和高温作用下混凝土侵蚀试验、微观试验. 通过分析混凝土试件质量变化、动弹性模量、侵蚀产物的成分与含量、硫酸根离子含量，结合微观测试，揭示半浸泡和硫酸盐环境下高温-干湿循环作用下混凝土损伤劣化规律. 结果表明：硫酸盐侵蚀初期，硫酸盐侵入浸泡区混凝土内部，促进水化作用，混凝土内部的AFT、石膏会填充初始缝隙，产物起到填充作用及骨架作用；后期产物量继续增大会对混凝土造成破坏，动弹性模量下降12%～30%；吸附区的混凝土同时受到干湿循环和热循环，2种循环会加剧毛细作用、扩散作用，使盐类在混凝土内部易产生结晶，热循环会加速骨料和水泥基体脱离，形成更多的孔隙，有利于盐类继续侵入；硫酸钠的物理结晶前期填充作用对强度有提升，质量提升0.50%～1.75%，但后期的破坏作用更加严重.
Abstract:To address the damage and deterioration of concrete materials in a sulfate environment in marine engineering, a concrete erosion test and microscopic test under different concentrations of sulfate solution and high temperature in the semi-immersed environment were carried out. By analyzing the mass change, dynamic elastic modulus, composition and content of eroded products, and sulfate ion content of concrete specimens and conducting the microscopic test, the damage and deterioration law of concrete under the high temperature and dry-wet cycle in semi-immersed and sulfate environment was revealed. The results show that in the early stage of sulfate erosion, sulfate invades the interior of concrete in the immersion zone and promotes hydration. The ettringite (AFT) and gypsum inside the concrete fill the initial gap, and the products play a filling and skeleton role. However, the continuous increase of the product amount in the later stage causes damage to the concrete, and the dynamic elastic modulus decreases by 12%–30%. The concrete in the adsorption zone is subjected to both the dry-wet cycle and the thermal cycle. The two cycles aggravate the capillary and diffusion effects so that the salt is easy to crystallize inside the concrete. Additionally, the thermal cycle accelerates the separation of aggregate and cement matrix, forming more pores, which is conducive to the continued intrusion of salt. The filling effect in the early stage of sodium sulfate crystallization improves the strength, and the mass increases by 0.5%–1.75%. However, the damage effect in the later stage is more serious.
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Key words:
- concrete in marine engineering /
- sulfate erosion /
- semi-immersion /
- thermal cycle /
- dry-wet cycle
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图 2 不同浓度及温度下质量变化率
Figure 2. Mass change rate at different concentrations and temperatures
图 3 不同浓度及温度下试件的相对动弹性模量
Figure 3. Relative dynamic elastic modulus of specimens at different concentrations and temperatures
图 9 10%浓度、不同温度下的微观结构
Figure 9. Microstructure at 10% concentration under different temperatures
图 10 温度60 ℃、不同浓度下的微观结构
Figure 10. Microstructure at 60 ℃ under different concentrations
表 1 混凝土配合比
Table 1. Proportion of concrete mix
kg/m 材料 水 水泥 粉煤灰 砂 小石 中石 用量/（kg·m−3） 157 279 70 736 220 885 
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表 2 试验工况
Table 2. Test conditions
编号 Na2SO4 溶液
浓度/%温度/℃ 侵蚀
时间/dC0T20 0 20 0，30，60，
90，120，150C0T40 0 40 C0T60 0 60 C5T20 5 20 C5T40 5 40 C5T60 5 60 C10T20 10 20 C10T40 10 40 C10T60 10 60
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