CHLORIDE FIXATION CAPACITY OF CEMENT MANUFACTURED FROM MUNICIPAL SOLID WASTES

为研究城市生活垃圾（EC）水泥在水化和碳化过程中氯离子的行为，探讨其在钢筋混凝土构件中的适用性，通过对水泥氯离子含量与钢筋锈蚀关系的试验，确定了目标氯离子含量为0.05%的EC，除普通波特兰水泥外，还使用0.07%和0.1%的水泥。制备了水灰比为0.40的水泥浆体，用于分析孔溶液和水化产物。还制备了水灰比为0.60的混凝土，其中嵌入了D13钢筋，用于加速腐蚀试验（重复在3%NaCl溶液中浸泡3天和在空气中暴露4天）从孔隙溶液组成分析的结果来看，当使用EC时，在混合后1天内，大部分氯离子与水泥矿物和/或水泥水化产物固定，而在掺加NaCl的氯离子含量与EC相当的普通硅酸盐水泥中，大部分氯离子在搅拌后3天内也被固定。孔隙溶液的氯离子和氢氧化物离子浓度之比远低于3：5，这被认为是即使当试样被碳化时的钢腐蚀的阈值。从加速腐蚀试验的结果来看，当使用任何一种水泥时，都没有发现来自内部氯化物的钢筋腐蚀。总之，人们认为，从城市废物制造的水泥具有足够的能力，以固定内部氯化物与水泥矿物和/或水泥水化产物。

The aim of this study is to investigate behavior of chloride in cement manufactured from municipal solid wastes (EC) during hydration and carbonation and to discuss on the applicability of this cement to reinfoced concrete members through the experiments regarding the relationship between chloride content of cement and steel corrosion.EC whose target chloride contents were 0.05%, 0.07% and 0.1% were used as cement in addition to normal portland cement. Cement pastes with a water cement ratio of 0.40 were prepared for the analysis of pore solution and hydration products. Concretes with a water cement ratio of 0.60, where a D13 steel bar was embedded, were also prepared for an acceleration corrosion test (repetition of 3 day immersion in NaCl 3% solution and 4 day exposure in air)From the results of pore solution composition analysis, most of chloride ions were fixed with cement minerals and/or cement hydration products within 1 day after mixing when EC was used, while most chloride ions were also fixed within 3 days after mixing when normal portalnd cement whose chloride content was equal to that of EC by adding NaCl was used. The ratio of chloride ion and hydroxide ion concentrations of pore solution was extremely lower than 3 to 5 that is said to be a threshold value of steel corrosion even when a specimen was carbonated. From the results of acceleration corrosion tests, steel corrosion derived from internal chloride could not be found when either of cement was used. In conclusion, it is thought that cement manufactured from municipal wastes has a capacity enough to fix internal chloride with cement mineral and/or cement hydration products.