自然环境下氯氧镁水泥的长期水化产物及其相转变规律

为了研究氯氧镁水泥的长期耐久性机理,用XRD分析了我国实际使用12~16a的氯氧镁水泥材料的物相组成,探讨了氯氧镁水泥在自然环境下的长期水化产物与转变规律。结果表明,氯氧镁水泥的长期水化产物,在室内大气环境下主要是氯氧化镁5Mg(OH)2.MgCl2.8H2O(5.1.8)和氢氧化镁Mg(OH)2,在室外露天环境下主要是Mg(OH)2、5.1.8、碳化氯氧化镁Mg(OH)2.MgCl2.2MgCO3.6H2O(1.1.2.6)]和水菱镁矿4MgCO3.Mg(OH)2.4H2O(4.1.4)]。在露天的使用环境中,没有经过改性、或者改性效果不佳的氯氧镁水泥材料中的主要水化产物5.1.8,同时发生了分解-碳化作用和碳化-分解作用,其初级分解产物是Mg(OH)2,初级碳化产物是1.1.2.6,终极碳化产物是4.1.4和MgCO3。氯氧镁水泥材料结构中大量形成4.1.4,是导致其耐久性失效的根本原因。

Long-term Hydration Products and Phase Transition of the Magnesium Oxychloride Cement Materials Exposed to Natural Environment

To research long-term durability mechanism of magnesium oxychloride cement,the paper analyzed magnesium oxychloride cement phase composition by XRD,which had been used about 12-16 years in natural environment in China.By the assaying,the paper probed into the long-term hydration products and their phase transition.It is discovered that the main long-term hydration products of the cement are magnesium oxychloride and brucite indoor,and magnesium oxychlorocarbonate and hydromaynesite outdoor.The magnesium oxychloride will be decomposed and carbonized if not being modified or the additive being not good enough.Early decomposition product is Mg(OH)2,early carbonization product is magnesium oxychlorocarbonate,and final carbonization product is hydromagnesite and magnesium carbonate.The formation of hydromagnesite is the fundamental factor of durability decay.