引气与防水组分对混凝土渗透性与抗冻性的影响

发布时间：2018-06-12 13:26

本文选题：渗透性 + 抗冻性　；参考：《哈尔滨工业大学》2015年硕士论文

【摘要】：冻融破坏是混凝土最常见的破坏现象之一,尤其是在冻融交替的地区。在引气剂与防水剂单独或者综合作用下,混凝土的抗冻及抗渗性能会得到很大的改善。国内外学者研究的大部分为引气剂或者防水剂单独作用的情况,因此,本文旨在研究它们的复合作用效果。选取典型配合比的混凝土,采用电通量法和表面气体渗透仪分析其抗渗性;利用快速冻融试验评价其抗冻性能。最后分析了硬化混凝土的气泡参数、孔结构与孔径分布及界面过渡区结构。首先,研究分析了蒸汽养护和常温养护两种制度下,引气剂对混凝土的抗冻及抗渗性能的影响规律。研究结果表明:无论蒸汽养护还是常温养护,引气剂掺量大的混凝土的抗冻性及抗渗性较好,但其初始强度相对较低。从微观角度分析,在引气剂掺量相同的前提下,蒸养混凝土的气泡间距系数大于常温养护的,但是其最可几孔径却小于常温养护的,蒸养混凝土中含有较多的大孔隙(1000nm)和小孔隙(10nm),而常温养护混凝土中则含有较多的对混凝土抗冻及抗渗性能有利的10nm~100nm的孔隙;蒸养混凝土的界面过渡区晶体含量相对较多,未受冻时其界面区或者浆体中已经有少许的小裂缝存在,蒸养混凝土的冻融破坏可能同时发生在界面过渡区和浆体,而常温养护混凝土的破坏主要集中在界面过渡区。其次,研究了常温养护制度下,引气与防水组分对混凝土的复合作用。研究结果发现:引气剂和防水剂的加入都会使混凝土的强度有所下降,但是它们对混凝土的抗冻及抗渗性能改善效果明显;有机硅防水剂及引气剂均可以显著改善混凝土的抗水、氯离子渗透能力,渗透结晶型防水剂则可以全面改善的混凝土的抗渗性,冻融循环200次时,渗透结晶型防水剂的加入使得引气量相同的混凝土的表面气体渗透深度最多下降了19.18%,其渗透结晶型产物主要为钙矾石(Aft)、氢氧化钙(CH)、水化硅酸钙(C-S-H)及碳酸钙(Ca CO3),其渗透深度约为8~12mm;防水剂的加入使混凝土的气泡间距系数有减小的趋势,抗冻性及抗渗性优异的未冻混凝土的气泡间距系数仅为138μm,比空白混凝土低257μm;防水剂的掺入使得混凝土中10~100nm的孔隙的比例大大,使得混凝土的最可几孔径有减小的趋势,使得混凝土的界面及浆体结构更加均匀、连续、密实,其中渗透结晶型防水剂的作用效果尤为明显。最后,确定了混凝土的最佳外加剂组成为:掺1.5?引气剂+1.0%有机硅防水剂+外涂0.8~1.0mm渗透结晶防水剂。经过300次冻融循环后,其质量损失仅为0.81%,其抗冻等级达到了DF300。
[Abstract]:Freeze-thaw failure is one of the most common failure phenomena in concrete, especially in the regions where freeze-thaw alternate. Under the action of air-entraining agent and water-repellent agent alone or synthetically, the frost resistance and impermeability of concrete will be greatly improved. Scholars at home and abroad mostly study the situation of air-entraining agent or water-repellent acting alone, therefore, the purpose of this paper is to study their compound effect. The concrete with typical mix ratio was selected to analyze its impermeability by electric flux method and surface gas permeation instrument, and its frost resistance was evaluated by rapid freeze-thaw test. Finally, the bubble parameters, pore structure, pore size distribution and interface transition zone structure of hardened concrete are analyzed. Firstly, the influence of air entraining agent on the frost resistance and impermeability of concrete under steam curing and normal temperature curing is studied. The results show that the concrete with large amount of air entraining agent has good frost resistance and impermeability, but its initial strength is relatively low, regardless of steam curing or normal temperature curing. From the microscopic point of view, on the premise of the same air entraining agent content, the bubble spacing coefficient of steaming concrete is larger than that of room temperature curing, but the most suitable pore size is smaller than that of room temperature curing. The steaming concrete contains more macropores (1000 nm) and small pores (10 nm), while the curing concrete at room temperature contains more 10nm~100nm pores which are favorable to the frost resistance and impermeability of concrete, and the interfacial transition zone of steaming concrete contains relatively more crystals. There are a few cracks in the interface zone or the slurry body when the concrete is not frozen. The freeze-thaw failure of the steaming concrete may occur in the interfacial transition zone and the slurry at the same time, while the damage of the curing concrete at room temperature is mainly concentrated in the interfacial transition zone. Secondly, the compound action of air entrainment and waterproof component on concrete under normal temperature curing system is studied. The results show that both air-entraining agent and water-repellent agent can decrease the strength of concrete, but they can improve the frost resistance and impermeability of concrete obviously. Both silicone water-repellent and air-entraining agent can significantly improve the water resistance of concrete. The permeable capacity of chloride ion can be improved significantly. The permeability of concrete with permeable crystalline waterproof agent can be improved completely, and when freeze-thaw cycles are 200 times, The penetration depth of the surface gas of concrete with the same amount of air entraining decreased by 19.18% with the addition of permeable crystalline water-repellent agent. The main products of permeation crystallized were ettringite, calcium hydroxide, calcium silicate (C-S-H), calcium carbonate and calcium carbonate. The permeation depth is about 812 mm, and the air bubble spacing coefficient of concrete decreases with the addition of water-repellent. The bubble spacing coefficient of unfrozen concrete with excellent frost resistance and impermeability is only 138 渭 m, which is 257 渭 m lower than that of blank concrete. The interface and slurry structure of concrete are more uniform, continuous and dense, and the effect of permeable crystalline waterproof agent is especially obvious. Finally, the optimum admixture composition of concrete is determined as follows: 1.5? Air entraining agent 1.0% silicone water repellent was coated with 0.8~1.0mm permeable crystalline waterproof agent. After 300 freeze-thaw cycles, the mass loss was only 0.81%, and the frost resistance grade reached DF300.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528

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