【作者】 肖婷；

【导师】 方永浩；

【作者基本信息】 河海大学 ， 材料学， 2005， 硕士

【摘要】 混凝土的耐久性一直是水泥混凝土界和工程界最为关心的问题之一,近年来其研究已经从单一劣化因素转向多种劣化因素对混凝土耐久性的影响。水泥基材料的冻融和碳化这一对耐久性问题,均会影响其结构和渗透性,故互相关联;水的渗透（渗流）导致水泥石组分的溶蚀,同样影响水泥基材料的上述性能,因此也与冻融和碳化特性有关。本文开展了对冻融作用下水泥基材料不同的破坏特征、裂缝状态下水泥基材料渗透溶蚀特性的研究;通过对冻融过的试件进行碳化试验,以及对碳化过的试件进行冻融试验,着重讨论了冻融和碳化这两种作用的相互影响;同时通过氮气吸附以及SEM等方法从微观角度对水泥基试件在上述不同作用下结构的变化进行了讨论。 冻融循环试验表明,由于净浆、砂浆和混凝土这三种水泥基材料孔结构的不同,使得其破坏时的外观和断面形状各不相同。对试件细观结构的分析得出,硬化水泥浆体的冻融破坏为由表及里较为均匀的破坏。冻融过程中内部的结构变得疏松,大孔径的孔增多,总孔径增大。 对水泥基试件碳化前后的细观结构分析得出,水泥石碳化后,原先的孔被细小的碳酸钙晶粒填充,使总孔隙率降低,孔径细化。水泥浆体的水灰（胶）比越大,碳化对硬化水泥石比表面积和孔结构的影响越大。 考虑到两种因素的相互作用,本文通过试验得出结论:碳化对水泥基试件的抗冻融能力有一定的提高作用,但是作用并不是很显著;冻融循环作用对水泥基试件的抗碳化能力有削减的作用。由此,讨论分析了冻融和碳化组合作用时混凝土碳化过程的经时变化。 裂缝状态下水泥基试件的渗透试验表明,随着渗透时间的延长,试样渗透液的渗透水量、Ca²⁺含量、pH值和电导率逐渐降低。渗透开始阶段,各项指数有上升的趋势,然后逐渐降低,直至趋于稳定。更多还原

【Abstract】 The durability of concrete is one of the key problems in cement and concrete field that many scholars are concerned with. In recent years, the focus of durability research is transferred from single degradation factor to multi ones. Two of durability indexes of cement-based materials, freeze-thaw and carbonation, are related with each other, for that they both affect and are affected by structure and permeability. Water permeability is related with these two indexes, because it will cause erosion and changes above. So in this paper, damage features of cement-based materials after freeze-thaw, permeability behavior with a micro-crack, especially the interactive effect of freeze-thaw and carbonation are researched. BET SEM methods are also used to study the relevant mechanisms.Freezing and thawing test shows that the figuration and cross-section of cement-based materials (paste, mortar and concrete) are different after they damage because of their different pore structures. Study on the micro-structure of specimens’ shows that freeze-thaw damage is a kind of uniform one, which happens from the surface to the center. And the interior becomes looser; the amount of large pores increases, so the total pore volume becomes larger.After it is carbonated, the pores of hardened cement paste are filled with finer calcium carbonation crystals. So the total pore volume decreases, and the pores become finer. The larger ratio of W/C, the more effect carbonation has to the surface area and pore structure of hardened cement paste.Considering the interaction of these two indexes, it can be concluded from the experiment that carbonation has some helpful effect on samples’ ability to resist freeze-thaw, but the effect is not notable; on the other hand, the freeze-thaw cycling will accelerate carbonation. And the changing process with time of concrete under the interaction of carbonation and freeze-thaw is analyzed.The result of the leaching test to the sample with a micro-crack shows that the amount, the pH value, electric conductivity and Ca2+ content of leached water decrease with the prolong of time. At the beginning, all indexes have a trend of increasing, then decrease, and cease in the end.更多还原