CHLORIDE FIXATION CAPACITY OF CEMENT MANUFACTURED FROM MUNICIPAL SOLID WASTES

为了研究城市生活垃圾水泥中氯离子在水化和碳化过程中的行为，通过水泥中氯离子含量与钢筋锈蚀关系的试验，探讨了该水泥在钢筋混凝土构件中的适用性。在普通硅酸盐水泥的基础上，将目标氯离子含量分别为0.05%、0.07%和0.1%的城市生活垃圾制成水泥。制备了水灰比为0.40的水泥净浆，用于分析气孔溶液和水化产物。对水灰比为0.60的D13钢筋混凝土进行了加速腐蚀试验(在NaCl3%溶液中反复浸泡3d，在空气中暴露4d)。从孔溶液成分分析结果可知，使用EC时，大部分氯离子在搅拌后1d内被水泥矿物和/或水泥水化产物固定，而当使用普通Portaland水泥时，大部分氯离子也在搅拌后3d内固定。孔溶液中氯离子与氢氧化物离子浓度之比极低，甚至在碳化时也是钢材腐蚀的临界值。从加速腐蚀试验结果来看，使用两种水泥都没有发现钢材由内部氯离子引起的腐蚀。总之，人们认为由城市垃圾制成的水泥具有足够的能力将内部氯化物与水泥矿物和/或水泥水化产物固定在一起。

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.