为了探讨缓凝剂硼砂(B)对磷酸镁水泥(MPC)的作用机理,测试和分析了不同掺量硼砂(B)的磷酸镁水泥(MPC)浆体的凝结时间、pH值、体系温度以及硬化体的强度和微观结构.结果表明:硼砂在一定掺量范围内对磷酸镁水泥(MPC)浆体有较明显的吸热降温促进作用和调节pH值作用,两种作用均可减慢浆体的水化反应速度且进一步影响硬化体的微观结构形貌和强度.由此推论硼砂在磷酸镁水泥(MPC)浆体中,除在MgO表面形成保护膜外,还通过降低体系温度和调节浆体pH值进而减慢水化反应速度来延缓浆体的凝结,随着硼砂(B)掺量的变化,不同因素起主导作用.
To probe into the mechanism of the effects of retardant borax on magnesia-phosphate cement,the setting time、pH and system temperature,induration intensity and micromorphologies of magnesiaphosphate cement pastes with different borax contents in hydration reactions were tested and analysized.The results indicated that borax causes obvious endothermic effect,and PH effect on MPC paste by which early hydration rate of MPC paste might be slowered and then the strength and micromorphologis of hydrated MPC were further affected.It is presumed that setting time of MPC paste is adjusted by both the formation of the precipitation barrier films and slowered hydration rate of MPC paste caused by cooling effect and higher pH value,and different factors play a leading role with respect to different B contents.
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