预加载活性粉末混凝土在硫酸盐作用下的耐久性研究

发布时间：2018-07-23 19:29

【摘要】：活性粉末混凝土具有超高的力学性能和良好的耐久性能,尤其适用于对耐久性要求高的结构,因此研究活性粉末混凝土多因素耦合作用下的耐久性具有重要的意义。本文对预加载活性粉末混凝土在硫酸盐干湿和冻融循环耦合作用下的耐久性进行了研究,以水泥种类、粉煤灰和矿粉掺量为主要变量,以不同耦合作用次数下的相对动弹性模量、质量损失率、抗压强度和抗压强度耐蚀系数为主要评价指标,结合扫描电子显微镜(SEM)分析活性粉末混凝土微观形貌的变化,探究活性粉末混凝土在硫酸盐干湿和冻融循环耦合作用下的损伤机理。主要结论如下： (1)在硫酸盐干湿和冻融循环耦合作用下,活性粉末混凝土的耐久性良好。宜优先选用抗压强度和抗压强度耐蚀系数作为其耐久性的评价指标,其次是相对动弹性模量,不宜选用质量损失率作为其耐久性的评价,耦合作用过程中质量损失率变化很小。 (2)在硫酸盐干湿和冻融循环耦合作用下,预加载活性粉末混凝土的抗侵蚀能力明显高于高性能混凝土的抗侵蚀能力；粉煤灰替代硅粉能够提高活性粉末混凝土的抗硫酸盐干湿和冻融循环耦合作用的能力；矿粉的掺入能够改善活性粉末混凝土的耐久性；高抗硫酸盐水泥活性粉末混凝土的抗硫酸盐干湿和冻融循环耦合作用的能力优于普通硅酸盐水泥活性粉末混凝土。 (3)硫酸盐干湿和冻融循环耦合作用对混凝土微观形貌产生的影响很大。通过SEM-EDS观察发现：C50高性能混凝土耦合循环作用后,Ca(OH)2含量减少,粉煤灰颗粒的火山灰反应程度较低,耦合作用后生成了大量AFm晶体及二水石膏晶体等腐蚀产物。活性粉末混凝土耦合作用后,生成了少量AFm晶体、二水石膏晶体,但由于活性粉末混凝土基体本身结构致密未观察到Ca(OH)2的存在；高抗硫酸盐活性粉末混凝土耦合循环后,水化石榴石的生成,提高了混凝土的密实度,降低了SO42-和Ca2+反应的可能性,抑制了膨胀性石膏晶体的生成,从而提高了活性粉末混凝土的耐久性。
[Abstract]:Reactive powder concrete (RPC) has super high mechanical properties and good durability, especially for structures with high durability requirements. Therefore, it is of great significance to study the durability of reactive powder concrete (RPC) under multi-factor coupling. In this paper, the durability of pre-loaded reactive powder concrete under the coupling of sulphate drying and wet and freeze-thaw cycle is studied. The main variables are the type of cement, the amount of fly ash and mineral powder. Taking the relative dynamic modulus of elasticity, mass loss rate, compressive strength and corrosion resistance coefficient of compressive strength and compressive strength as the main evaluation indexes under different coupling action times, the microstructure of reactive powder concrete (RPC) was analyzed by scanning electron microscope (SEM) (SEM). The damage mechanism of reactive powder concrete (RPC) under the coupling of sulphate drying and wet freezing and thawing was investigated. The main conclusions are as follows: (1) under the coupling of sulphate drying and wet freezing and thawing the durability of reactive powder concrete is good. The compressive strength and the corrosion resistance coefficient of compressive strength should be selected as the evaluation index of its durability, and the relative dynamic modulus of elasticity should be followed, and the loss rate of mass should not be chosen as the evaluation of its durability. The mass loss rate changes little during the coupling process. (2) under the coupling of sulphate drying and wet freezing and thawing the corrosion resistance of pre-loaded reactive powder concrete is obviously higher than that of high performance concrete. The substitution of fly ash for silica powder can improve the coupling ability of reactive powder concrete against sulfate dry-wet and freeze-thaw circulation, and the addition of mineral powder can improve the durability of reactive powder concrete. The coupling ability of high resistance cement reactive powder concrete to sulfate drying and freeze-thawing cycles is better than that of ordinary Portland cement reactive powder concrete. (3) the coupling effect of sulfate dry wet and freeze-thaw cycle is better than that of ordinary Portland cement reactive powder concrete. The microstructure of concrete has great influence. By SEM-EDS observation, it was found that the content of Ca (OH) _ 2 decreased and the reaction degree of pozzolanic ash of fly ash particles was lower after the coupling cycling of C _ (50). A large number of corrosion products such as AFm crystals and gypsum dihydrate crystals were formed after coupling action. A small amount of AFm crystal and gypsum dihydrate crystal were formed after the interaction of reactive powder concrete, but the existence of Ca (OH) 2 was not observed due to the dense structure of reactive powder concrete matrix. The formation of hydrated garnet improves the compactness of concrete, reduces the possibility of reaction between so _ 42- and Ca2, inhibits the formation of expansive gypsum crystal, and improves the durability of reactive powder concrete.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU528

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