Na_2HPO_4·12H_2O对磷酸镁水泥水化硬化特性的影响

Effect of Na_2HPO_4·12H_2O on Hydration and Hardening Properties of Potassium and Magnesium Phosphate Cement Paste

研究了适量掺加Na_2HPO_4·12H_2O对新型磷酸镁水泥(MKPC)浆体水化硬化过程中的-pH值、体系温度、凝结时间、流动性以及强度发展等的影响.结果表明:Na_2HPO_4·12H_2O在MKPC浆体中的溶解和相变过程吸收了大量热量,从而降低了MKPC浆体的初始温度,延缓了浆体的温度上升速度,提高了MKPC浆体的pH值;上述因素导致MKPC浆体中KH_2PO_4和MgO的溶解度以及离子溶出速度降低,从而有效地控制了MKPC浆体的凝结时间和早期水化反应速度,改善了MKPC浆体的流动性;Na_2HPO_4·12H_2O还参与了系统的水化反应,使MKPC硬化体后期强度稳定增长.

A small amount of Na2HPO4·12H2O was mixed into magnesium phosphate cement（MPC） paste to investigate its effect on pH value,fluidity,hydration temperature and strength development of MKPC paste and on mineralogical composition and microstructural morphology of hydration products of hardened MKPC paste.Results indicate that,Na2HPO4·12H2O absorbs a great deal of heat of dissolution and transformation in MKPC paste,thus the initial temperature and the temperature rise rate of MKPC paste is decreased.The pH value of MKPC paste is raised by adding Na2HPO4·12H2O.The solubility and ion release rate of KH2PO4（K） and MgO（M） is decreased by above factors,and this effectively delays the setting time and the early hydration rate of MKPC paste and increases the fluidity of MKPC paste. Na2HPO4·12H2O also participates in hydration reaction resulting in the sustainable growth of late strength of hardened MKPC paste.