多因素耦合作用下水泥基材料损伤劣化研究

发布时间：2018-05-10 17:12

本文选题：砂浆 + 混凝土　；参考：《东南大学》2017年硕士论文

【摘要】：在海洋或者盐湖中服役的水泥基材料由于内外部诸多因素的作用而发生损伤劣化,材料逐渐丧失服役性能达不到预定的使用寿命。外部因素主要包括材料所受到的应力作用、盐湖海水中高浓度的侵蚀性离子、浪溅冲刷以及潮汐区造成的特殊浸泡制度以及一些温湿度变化等。而内部因素主要有水泥基材料的组成、结构以及辅助胶凝材料品种及掺量等。水泥基材料在不同服役环境中的耐久性一直是工程和学术界关注的热点。本文主要针对处于海洋潮汐浪溅冲刷区中服役的水泥基材料,以砂浆和混凝土试件为研究对象,研究弯曲荷载-干湿循环-复合盐溶液耦合作用下水泥基材料的损伤劣化过程。重点研究了水泥基材料在多因素耦合作用下,微结构损伤累积规律,为多因素耦合作用下混凝土结构使用寿命的预测提供理论依据。本文以相对动弹性模量为测试指标,研究了弯曲荷载-干湿循环-复合盐溶液耦合作用下砂浆以及混凝土试件损伤劣化过程。实验结果表明:弯曲荷载-干湿循环-复合盐溶液耦合作用下砂浆试件的损伤劣化过程可以分为三段:初始劣化段、性能改善段和性能劣化段。增大弯曲荷载应力比、提高硫酸盐浓度以及加速干湿循环频率都会缩短性能改善段并且提前性能劣化段,从而加速了砂浆试件的损伤劣化。提高氯盐浓度在一定程度上缓解了硫酸盐侵蚀。长期浸泡下的试件性能不降反升,相对动弹性模量一直保持在1以上。而水胶比的降低以及矿渣粉和粉煤灰等矿物掺合料的掺入提高了砂浆试件的抗侵蚀性能。此外,本文利用X-CT和压汞法(MIP)测试弯曲荷载-干湿循环-复合盐溶液耦合作用下砂浆试件孔结构变化规律。利用XRD测试了盐类侵蚀前后水化产物与腐蚀产物含量变化。利用环境扫面电镜(ESEM)观察了固相形貌及界面过渡区在侵蚀前后变化。试验结果显示:侵蚀后砂浆试件的受拉区孔隙率、有害孔、腐蚀产物以及形貌损伤程度明显高于受压区。而且应力比的提高、硫酸盐浓度的提高和干湿循环频率的加快都会加块砂浆试件损伤劣化。氯盐浓度提高减缓了硫酸盐对砂浆试件的侵蚀。长期浸泡下砂浆试件的孔隙率不升反降,水化产物和腐蚀产物的填充作用提高了抗侵蚀性能。低水胶比和矿物掺合料的加入降低了孔隙率改善了孔结构,很大程度上减缓了盐溶液对砂浆试件的侵蚀。
[Abstract]:Cement based materials serving in sea or salt lakes are damaged and degraded due to many internal and external factors, and the service performance of the materials is gradually lost to the intended service life. The external factors mainly include the stress of the material, the high concentration of erosive ions in salt lake seawater, the special immersion system caused by the wave splash and the tidal zone, and some changes of temperature and humidity, etc. The internal factors include the composition, structure of cement-based materials and the variety and content of auxiliary cementing materials. The durability of cement-based materials in different service environments has been a hot topic in engineering and academic circles. In this paper, the damage and deterioration process of cement-based materials under the coupling of bending load-dry-wet cycle and composite salt solution is studied by taking mortar and concrete specimen as the research object, aiming at the cement-based materials in the marine tidal wave and splash scouring area. In this paper, the damage accumulation law of cement based materials under multi-factor coupling is studied, which provides a theoretical basis for predicting the service life of concrete structures under multi-factor coupling. Taking the relative dynamic modulus of elasticity as the test index, the damage deterioration process of mortar and concrete specimens under the coupled action of bending load-dry-wet cycle and composite salt solution is studied in this paper. The experimental results show that the damage degradation process of mortar specimens under the coupling of bending load-dry-wet cycle and composite salt solution can be divided into three stages: initial degradation section, performance improvement section and performance degradation section. Increasing the bending load-stress ratio, increasing the sulfate concentration and accelerating the drying and wet cycle frequency can shorten the performance improvement section and advance the performance deterioration section, thus accelerating the damage deterioration of mortar specimens. Increasing chloride concentration alleviates sulfate erosion to some extent. The properties of the specimens soaked for a long period of time have not decreased but increased, and the relative dynamic modulus of elasticity has been kept above 1. The decrease of water-binder ratio and the addition of mineral admixtures such as slag powder and fly ash improve the corrosion resistance of mortar. In addition, the pore structure of mortar specimens under the coupling of bending load-dry-wet cycle and composite salt solution was tested by X-CT and mercury injection method. The content changes of hydration products and corrosion products before and after salt erosion were measured by XRD. ESEM was used to observe the morphology of solid phase and the change of interfacial transition zone before and after erosion. The results show that the tensile porosity, harmful pores, corrosion products and the damage degree of morphology of corroded mortar specimen are obviously higher than those of compressive zone. Moreover, the increase of stress ratio, the increase of sulfate concentration and the acceleration of dry-wet cycle frequency will result in the damage deterioration of mortar specimens. The increase of chloride concentration alleviates the erosion of mortar specimen caused by sulfate. After a long period of immersion, the porosity of mortar samples does not rise or decrease, and the filling of hydration products and corrosion products improves the corrosion resistance. The low water / binder ratio and mineral admixture decrease the porosity and improve the pore structure, and to a great extent reduce the erosion of mortar specimens caused by salt solution.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528

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