用水量对硅酸盐水泥石泛白的影响及作用机理

Effects of Water Amount on Efflorescence of Portland Cement-Based Artificial Stone and Its Mechanisms

摘要:

研究了用水量对硅酸盐水泥石的初次和二次泛白程度、泛白物质组成以及形貌的影响，并结合低场核磁共振分析了水泥石中可蒸发水的横向弛豫特征和状态演变.结果表明：随着水灰比的增加，硅酸盐水泥石的泛白程度不断加剧，泛白物质均以CaCO₃为主；减水剂掺量会直接影响CaCO₃的晶型，在同一水灰比（0.18）条件下，减水剂掺量为0.5%时泛白物质以立方状方解石和纺锤状文石为主，减水剂掺量增至1.0%时，泛白物质除了方解石，还有片状球霰石及少量钠盐；随着水化龄期的延长，硅酸盐水泥石中可蒸发水的弛豫时间分布逐渐趋向于短弛豫时间，高水灰比（0.30）条件下主峰的面积更大，毛细水含量更高，泛白更严重.因此，合理的减水剂掺量和水灰比是控制硅酸盐水泥石泛白的关键因素.

Abstract:

The effects of water amount on the primary and secondary efflorescence， composition and morphology of the efflorescence substance were investigated. And the transverse relaxation characteristics and state evolution of evaporable water in cement paste were studied by low field nuclear magnetic resonance spectroscopy. The results show that the efflorescence degree of Portland cement increases with increasing water to cement ratio. Additionally， the efflorescence substance is mainly calcium carbonate， while the content of superplasticizer directly affects the crystal form of formed calcium carbonate. With the same water to cement ratio （0.18）， the efflorescence substance is mainly cubic calcite and spindle aragonite when the content of superplasticizer is 0.5%， the efflorescence substance appears to be flaky aragonite and little sodium salt besides calcite， when the superplasticizer content increases to 1.0%. With the increase of the hydration period of cement， the relaxation time distribution of evaporable water of cement paste tends to be shorter. There is a higher main peak area with a higher water to cement ratio （0.30）. It indicates that the content of capillary water is higher， which leads to a more serious efflorescence degree. Therefore， the reasonable content of superplasticizer and water to cement ratio are the key factors to control the efflorescence of Portland cement stone.