磷酸钾镁水泥(MKPC)的速凝特性限制了其在更多工程领域的应用发展, 有效延长凝结时间是其工程化应用的关键技术之一。本研究使用硼砂/三乙醇胺复合缓凝剂, 深入研究了其对磷酸钾镁水泥凝结时间、抗压强度、物相组成、微观形貌、孔结构和水化放热等特性的影响, 并探讨了缓凝机理。结果表明: 在保障7 d抗压强度大于20 MPa条件下, 复合缓凝剂的使用, 可实现26~100 min的凝结时间调控; 三乙醇胺分子包覆MgO颗粒, 发挥阻水作用, 从而显著降低水化反应的标准水化放热速率与标准水化放热量, 达到缓凝效果; 试样中K-鸟粪石含量的减少与大于10 nm孔隙体积的增加是削弱抗压强度的主要原因。

The rapid setting characteristic of potassium magnesium phosphate cement (MKPC) limits its application and development in engineering fields. Effectively prolonging the setting time is one of the key technologies for its engineering application. In this study, the effect of borax/triethanolamine composited retarder on the setting time, compressive strength, phase composition, micromorphology, pore structure and hydration heat release properties of MKPC was studied, and the retarding mechanism was discussed. The results show that the setting time of 26~100 min can be controlled by using the composited retarder under the condition that the 7 d compressive strength is greater than 20 MPa. Triethanolamine molecule is adsorbed on the surface of MgO and plays a role in water blocking, which significantly reduces the standard hydration heat release rate and standard hydration heat release, and achieves the retarding effect. The decrease of K-struvite content and the increase of pore (larger than 10 nm) volume are the main reasons for the weakening of compressive strength.