高强混凝土内养护微胶囊的多级孔构筑及减缩机制研究

The existing internal curing Light Weight Aggregate has low water absorption ability and reduces the strength of concrete significantly. In order to reduce the granularity, improve the water absorption ability and internal curing effect of internal curing materials, the project is intended to prepare microcapsules with hierarchical pore structure and the shrinkage reducing mechanism is proposed. Based on the stable mechanism of the glass powder-pore forming agent foam, the composite foam with high stability is prepared via physical foaming method. The microcapsules with hierarchical pore structure is produced using spray-drying and fast heat-treatment process. The hierarchical pore structure of the microcapsules is designed by changing the composition of raw materials, preparation formulation and properties of pore forming agent. The shrinkage reducing mechanism of the internal curing microcapsules is studied. Microcapsules with hierarchical pore structure, high water absorption ability and remarkable shrinkage reducing effect is obtained, which provides new candidate materials for internal curing of high-strength concrete.

针对现有内养护轻骨料存在吸水率低、降低混凝土强度的问题，以减小内养护材料粒径、提高内养护材料吸水率和养护效果为目标，拟开展高强混凝土内养护微胶囊的多级孔构筑及减缩机制研究。在阐明玻璃粉-成孔剂复合泡沫浆体稳定机理的基础上,采用物理发泡法制备高稳定性复合泡沫浆体,利用喷雾干燥法与快速烧成法成型多级孔结构内养护微胶囊,通过调控材料组成、制备工艺参数和成孔剂特征参数,实现内养护微胶囊多级孔结构的可控调节,揭示内养护微胶囊减缩机制，获得具有多级孔结构、吸水率高、减缩效果好的内养护微胶囊，为高强混凝土内养护提供新的候选材料。

针对现有内养护轻骨料存在吸水率低、降低混凝土强度的问题，以减小内养护材料粒径、提高内养护材料吸水率和养护效果为目标，围绕多级孔结构内养护微胶囊的制备及其减缩机制开展研究，提出了一种采用废玻璃粉制备内养护微胶囊的新方法。该方法利用废玻璃粉制备玻璃粉颗粒稳定泡沫，采用喷雾干燥法成型微胶囊坯体，并采用悬浮烧结法进行烧结，得到多级孔结构内养护微胶囊。探明了玻璃粉颗粒稳定泡沫的最佳制备条件，揭示了玻璃粉颗粒稳定泡沫的稳定机理，当pH值7.5、没食子酸丙酯浓度0.4wt%、球磨时间8h时，可以制备超稳定的玻璃粉颗粒稳定泡沫。采用没食子酸丙酯对玻璃粉进行表面改性，提高玻璃粉的疏水性，具有部分疏水性的玻璃粉颗粒不可逆地吸附在气/液界面，得到超稳定的玻璃粉颗粒稳定泡沫。明确了内养护微胶囊的制备方法及最佳工艺参数，提出了内养护微胶囊孔结构和性能调控方法，采用喷雾干燥法成型微胶囊坯体，采用悬浮烧结法进行微胶囊的烧结，适宜的烧结温度为850℃，送料风速为1.6m/s，通过调控成孔剂种类和含量，可实现微胶囊孔结构和性能的调控。探明了内养护微胶囊的吸水-释水规律，揭示了内养护微胶囊的减缩机制，微胶囊浸水后72h左右完成饱水过程，在相对湿度97.5%条件下，饱水微胶囊可释放出95%以上的水分。当混凝土内部相对湿度降低时，饱水微胶囊逐渐释放内养护水，削弱混凝土的自干燥现象，大幅降低混凝土的自收缩。本项目提出的微胶囊制备方法对于制备多孔微球具有普适性，具有良好的应用前景。