MgO晶须增强磷酸镁水泥力学性能的研究

摘要

Strength and toughness of magnesium phosphate cement (MPC)can be significantly improved by the addition of MgO whisker owing to its high modulus and length/diameter ratio.The effects of water/binder ratio and the content of retarder on the mechanical properties of MgO-whisker-reinforced MPC were investigated.Distribution characteristics and hydration properties of MgO whisker in MPC were analyzed by SEM and gravimetric method,and the mechanisms of MgO whisker reinforced on the strengthening and MPC were discussed.Results showed that a high early age compressive or flexural strength gain can be achieved when MgO whisker was added (3% to 5% by mass) into mixes of the high water/binder ratio and retarder content.An overlap network structure of MgO whisker is formed leading to bridging action and crack deflection,which significantly improves the strength gain at early ages. Bond strength and compatibility between MgO whisker and MPC are improved as a result of MgO whisker hydration. With development of hydration,higher long-term compressive strength of MPC,but decreased long-term flexural strength with respect due to the weakened crack bridging effect exerted by the slimmed whisker is found.%MgO 晶须弹性模量高,长径比大,掺加到磷酸镁水泥(MPC)中可以产生增强增韧作用。研究了水料比、缓凝剂掺量不同时 MgO 晶须对 MPC 力学性能的影响,采用 SEM 和重量法研究了 MgO 晶须在 MPC 中的分布及水化,分析了 MgO 晶须增强 MPC 的机理。结果表明,掺加3%~5%的 MgO 晶须使 MPC 在水料比和缓凝剂掺量较高时获得良好的早期强度；MgO 晶须在 MPC 中搭接形成网络结构,并通过晶须桥联、裂缝偏转等作用,使 MPC 的早期力学性能显著增强；MgO 晶须参与水化,提高了晶须与 MPC 基体的握裹力和相容性；随着龄期延长,晶须水化程度加深,使 MPC 基体更加致密,后期抗压强度增长明显,但晶须的桥联作用逐渐减弱,MPC 的后期抗折强度增长幅度较小。