A Study on the Physical and Chemical Deterioration of Hardened Mortar due to Leaching Calcium

本研究的目的是通过从混凝土中浸出Ca^<2+>来确定混凝土质量的变化。本研究主要采用硬化砂浆进行电浸出试验，试验是通过电溶出试样中的Ca^<2+来实现的。并对水泥砂浆中Ca^2+的淋溶所引起的物理化学变化进行了研究。根据Ca（OH）_2和CSH的溶出量关系，可以看出Ca（OH）_2和CSH的溶出量在不同的水泥混合料、不同的时间和不同的深度上都是相关的。当Ca（OH）_2从砂浆中完全浸出时，剩余的CSH最多可达0.3g/cm ^3。在溶解过程中，固体的溶解度一般基本上可以用固体的溶解度和比表面积来评价。从这些观点可以得出结论，CSH在混凝土中的溶解度虽然比Ca（OH）_2小，但由于其表面积大，在混凝土服役初期就可以溶解。

The purpose of this study is to determine the change of concrete quality by leaching Ca^<2+> from concrete. In this investigation, the electrical leaching tests were mainly carried out by using hardened mortar, and these tests were set up as Ca^<2+> was electrically dissolved out from specimens. And the physical and chemical changes of hardened mortar due to the leaching Ca^<2+> were measured in this study. From these test results, the mechanisms of leaching Ca^<2+> from mortar were experimentally found out.According to the relation between the amount of Ca(OH)_2 and that of CSH, it can be recognized that leaching out of Ca(OH)_2 and CSH are related in all cement mixtures, durations and depth. Moreover, the remaining CSH can be estimated at most 0.3 g/cm^3 when Ca(OH)_2 was completely leached out from the mortar specimens.In dissolving process, it is general that the dissolubility of solid can be evaluated basically by the solubility and surface area of the solid. From these viewpoints, the authors can conclude that CSH in concrete can be dissolved at early stage of service time because of its large surface area, although the solubility of CSH is comparatively smaller than that of Ca(OH)_2.