多因素耦合作用下混凝土硫酸盐腐蚀性能研究

发布时间：2018-11-13 19:31

【摘要】：实际服役的混凝土结构暴露于复杂的硫酸盐环境中，其劣化破坏是由材料、物理、化学、应力等诸多因素共同作用、相互耦合导致的。在地下混凝土结构中，全部埋于或浸泡于地下硫酸盐环境中的混凝土构件会受到硫酸盐全浸泡腐蚀，而半埋或半浸泡于地下硫酸盐环境中的混凝土构件则会受到干湿循环腐蚀。同时，一面与腐蚀环境接触、而另一面暴露于空气中的混凝土构件受到的硫酸盐腐蚀称为单面腐蚀。本文对全浸泡腐蚀、干湿循环腐蚀和单面腐蚀分别进行试验研究，选取影响硫酸盐腐蚀的因素及其水平，即Na2SO4溶液浓度（2%、5%和10%）、水胶比（0.4、0.5和0.6）和粉煤灰掺量（0%、10%和20%），分析多因素耦合作用下混凝土硫酸盐腐蚀性能的退化规律，并对腐蚀过程进行理论解释。在全浸泡腐蚀试验中，抗压强度和对测声速随腐蚀时间的增加而表现出先增大后减小的趋势；对于强度损失率和腐蚀损伤度，腐蚀前期为负值且绝对值先变大后变小，腐蚀后期为正值且不断增大。引入腐蚀过渡层，硫酸盐腐蚀混凝土的过程就是腐蚀过渡层进一步劣化为腐蚀损伤层并不断向从外向里推进的。计算出腐蚀损伤层厚度，分析腐蚀损伤层混凝土的声速及其与未腐蚀层声速的比值随腐蚀时间的变化规律。正交试验分析表明：最强腐蚀组合是A3B3C1，最弱腐蚀组合是A1B1C2；Na2SO4溶液浓度影响最大，水胶比次之，粉煤灰掺量影响最小；并建立腐蚀损伤层厚度与腐蚀时间及因素的计算模型。在干湿循环腐蚀试验中，腐蚀损伤度和腐蚀损伤层厚度均为正值且随腐蚀时间增加而不断增大，每一次循环都经历了“腐蚀→填充→损伤→损伤累积→劣化、开裂”的腐蚀过程。与全浸泡腐蚀相比，干湿循环腐蚀更厉害，，且以硫酸盐物理结晶腐蚀为主，水分的传输在干湿循环硫酸盐腐蚀过程中起到了关键作用。Na2SO4溶液浓度对干湿循环条件下的混凝土硫酸盐腐蚀的影响显著。在单面腐蚀试验中，吸附区混凝土表现出腐蚀破坏形态不同的三个区域——水膜区、结晶剥落区和吸附结晶区；吸附区混凝土的腐蚀损伤层厚度大于浸泡区混凝土，吸附区粉煤灰混凝土腐蚀也较严重。浸泡区中的水和SO42-离子在湿度梯度和浓度梯度的作用下沿壁厚或底厚方向由外向里扩散；而吸附区中的水和SO42-离子在毛细压力作用下沿壁高度方向由下向上迁移，并在蒸发作用下水分散失，SO42-离子向表层聚集。
[Abstract]:Concrete structures in service are exposed to complex sulphate environment and their deterioration and failure are caused by the interaction and coupling of materials, physics, chemistry, stress and so on. In the underground concrete structure, all the concrete members buried in or immersed in the underground sulfate environment will be completely corroded by sulfate, while the half-buried or semi-immersed concrete members in the underground sulfate environment will be corroded by dry-wet cycle. At the same time, the sulphate corrosion of concrete members exposed to air on one side is called one-sided corrosion. In this paper, the total immersion corrosion, dry and wet cycle corrosion and single side corrosion were studied respectively. The factors affecting sulfate corrosion and their levels were selected, that is, the concentration of Na2SO4 solution (2% and 10%). Water / binder ratio (0.4g / 0.5 and 0.6) and fly ash content (010% and 20%) were used to analyze the degradation law of sulfate corrosion performance of concrete under multi-factor coupling, and the corrosion process was explained theoretically. In the whole immersion corrosion test, the compressive strength and the sound velocity showed a tendency of first increasing and then decreasing with the increase of corrosion time. For the strength loss rate and corrosion damage degree, the initial value of corrosion is negative and the absolute value first increases and then becomes smaller, and the latter stage of corrosion is positive and increasing. With the introduction of corrosion transition layer, the process of sulphate corrosion of concrete is the process of further deterioration of the transition layer into corrosion damage layer and continuously advancing from outward to outward. The thickness of corrosion damage layer is calculated and the variation law of sound velocity and the ratio of sound velocity to that of non-corrosive layer with corrosion time are analyzed. The results of orthogonal test show that the strongest corrosion combination is A3B3C1and the weakest corrosion combination is A1B1C2Na2SO4 solution concentration, the ratio of water to binder is the second, and the content of fly ash is the least, and the calculation model of corrosion damage layer thickness, corrosion time and factors is established. In the dry and wet cycle corrosion test, the corrosion damage degree and the thickness of corrosion damage layer are both positive and increase with the increase of corrosion time. Cracking "corrosion process." Compared with total immersion corrosion, dry and wet cycle corrosion is more severe, and sulfate physical crystallization corrosion is the main corrosion. The moisture transport plays a key role in the process of wet and dry cycle sulfate corrosion. The concentration of Na2SO4 solution has a significant effect on the sulphate corrosion of concrete under dry and wet cycle conditions. In the single side corrosion test, the concrete in the adsorption zone shows three regions with different corrosion failure patterns: the water film region, the crystalline spalling zone and the adsorption crystallization zone. The thickness of corrosion damage layer of concrete in adsorption zone is larger than that of concrete in soaking area, and the corrosion of fly ash concrete in adsorption zone is more serious. The water and SO42- ions in the soaking zone diffused along the direction of wall thickness or bottom thickness under the action of humidity gradient and concentration gradient. However, the water and SO42- ions in the adsorbed region migrate along the direction of the wall height under capillary pressure, and the water is lost under evaporation, and the SO42- ion accumulates to the surface layer.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU528

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