渗透结晶反应修复混凝土孔隙和裂缝的过程与机理研究

The core component of cementitious capillary crystalline waterproofing materials is unidentified today. In addition, the soluble silicate, which is used as capillary crystalline active substance, has defects, such as low solubility, and sodium hydroxide by-product which cause the alkali silica reaction when mixed with cement base materials. So, ammonium phosphate, magnesium silicofluoride and ethyl silicate, will be employed as active substance of capillary crystalline materials for repairing the pore and the crack of concrete, because of their high solubility, strong permeability and no harmful by-products. Some Influence factors on repairing effect will be studied, such as the kind of capillary crystalline substance, the kind of solvent, the surface tension of coating liquid, the viscosity of coating liquid, the content of active substance, the kind and the contend of catalyst, the content and the size distribution of pore, the time of curing and so on. According to the influence factors, the optimum repairing technology of concrete pore and crack will be presented. Moreover, the reaction between active substance and calcium hydroxide and the mixture of calcium hydroxide with calcium silicate gel, simulating the reaction between active substance and real concrete system, will be studied in kinetics and thermodynamics for demonstrating the repairing process and capillary crystalline reaction mechanism of pore and crack. At same time,a evaluation method of repairing effect of concrete pore and crack will be proposed based on neural network theory. In a word, the research will offer key techniques, theoretical foundation and evaluation method for repairing the pore and the crack, improving the impermeability, and prolonging the service life of concrete.

本项目针对传统水泥基渗透结晶型防水材料核心成分不明，硅酸盐渗透结晶活性物质存在溶解度小、生成氢氧化钠易引起碱硅反应的问题，拟采用溶解度大、渗透力强、无有害副产物产生的物质，如磷酸铵盐、六氟硅酸镁和硅酸乙酯，作为渗透结晶反应修复混凝土孔隙和裂缝的活性物质。通过研究渗透结晶活性物质种类、渗透剂类型、涂液表面张力、粘度、活性物质量、催化剂、孔隙率和孔径分布、养护时间等因素对孔隙和裂缝修复影响的规律，为混凝土孔隙和裂缝的修复提供关键技术。以氢氧化钙和氢氧化钙与硅酸钙的复合物模拟复杂的混凝土水化体系，研究其与活性物质的反应，得到渗透结晶反应的动力学、热力学参数，阐明渗透结晶活性物质修复孔隙和裂缝的过程与机理。利用神经网络分析法建立渗透结晶反应修复孔隙和裂缝效果的评价方法。通过研究，将为修复混凝土孔隙和裂缝，提高混凝土材料的抗渗性，延长混凝土材料的使用寿命，提供关键技术、理论基础和评价方法。

孔隙与裂缝被称为水泥基材料的“癌症”，其对强度、抗渗性、耐久性等产生重大的负面影响。以沉淀结晶修复原理为基础，通过引入无害的外源性物质，提高对孔隙与裂缝的修复效果，发展新的渗透结晶反应修复理论。研究内容及结论如下：. 首先，以砂浆吸水率和强度为指标，考察了渗透物质种类的影响。研究表明，硅酸乙酯40、磷酸铵、硫酸镁效果较好，分别可降低吸水率80%、30%、59%左右，提高抗压抗折强度分别为30%和19.64%、36.27%和12.39%、29.25%和19.52%。. 研究渗透条件对砂浆吸水率和强度的影响，表明刷涂方式、50%TEOS-乙醇浓度、涂刷5次、添加0.3%CTAB和0.5%TEA，砂浆吸水率分别降低了75%、50%、80%，40%、50%。早期涂刷、延长涂刷后的养护时间、合适的干燥程度等有利于降低吸水率。渗透条件对强度的影响不大。. 研究外源双渗透剂和三离子渗透对砂浆吸水率和强度的影响，表明乙酸钙分别复合硅酸乙酯和硅酸甲酯，吸水率分别下降17.59%和37.64%，抗压抗折强度分别提高了11%、17.43%和10.23%、2.54%。硫酸镁分别复合硅酸乙酯和硅酸甲酯，吸水率下降68.81%和86.85%，抗压抗折强度提高了7.52%、15.08%和31.55%、27.77%。硫酸镁复合硅酸乙酯涂刷三次，吸水率下降92.24%，抗压抗折强度提高了125.55%和85.47%。. 耐久性研究表明，涂刷乙酸钙复合硅酸乙酯后，其抗冻融性能、抗氯离子能力、抗硫酸根离子能力、抗盐酸能力、抗氢氧化钠能力、抗二氧化碳能力分别提高了50%-70%、50%-60%、60%-70%、50%-70%、50%-60%和60%左右。硫酸镁复合硅酸酯类对砂浆耐久性能提高好于乙酸钙复合硅酸乙酯。. 结合渗透结晶对砂浆吸水率、强度、耐久性影响，以及XRD、SEM、MIP和TG分析，提出了基于内在水化氢氧化钙的沉淀修复机理。提出外源性渗透结晶沉淀机理，包括原有水化骨架基础、水载体溶解渗透物、常压或加压渗透、沉淀填充与胶结等反应过程与机理。. 新外源性渗透结晶理论扩大了物质的选择范围，为改善和控制材料结构，制备防水、高强、致密、长寿命的水泥基材料，或废旧材料的补强加固，提供了另一种更加广阔的思路与技术路线。