环境温度对磷酸镁水泥凝结时间和强度发展的影响

Effect of Ambient Temperature on Setting Time and Strength Development of Magnesia-phosphate Cement

在较高环境温度条件下,磷酸镁水泥(MPC)足够长的凝结时间和高早强之间的矛盾影响其实际应用。研究了环境温度为15、20、25、30和35℃,硼砂掺量为3%、6%、9%和12%时,MPC净浆凝结时间和抗压强度的变化规律。并研究了高硼砂掺量的MPC浇注一段时间后提高环境温度对其早期强度的改善作用,测量MPC体系早期温升曲线,并与凝结时间和早期强度相联系。结果表明:环境温度越高,MPC净浆早期强度发展越快,但凝结时间明显缩短;硼砂掺量增加,MPC凝结延缓,但早期强度发展缓慢;MPC温升峰值越高,出现时间越早,早期强度发展越快,凝结时间越短。硼砂掺量为12%,环境温度为25℃时,MPC初凝时间为40min,浇注40min后提高温度至50℃养护10min,MPC净浆1.5h强度达到27.2MPa。提高硼砂掺量和浇注后的养护温度可使MPC凝结时间和早期强度都能满足实际要求。

The confrontation between the prolonged setting time and high early strength impairs the practical use of magnesia-phosphate cement （MPC） at a higher ambient temperature. The effect of ambient temperature on the setting time and strength development of MPC was investigated. The ambient temperatures used were 15, 20, 25, 30 and 35 ℃, and the borax contents used were 3%, 6%, 9% and 12%, respectively. An approach that the MPC paste after casting was cured for different periods at elevated ambient temperature was used to improve the early strength development of MPCs with a high borax content. The relationship between early temperature rise within MPC and setting time and early strength development of MPC were analyzed. The results show that a higher ambient temperature produces a faster early strength development and a quicker setting for MPC. At all ambient temperatures, the setting time was delayed and the early strength decreased with increasing the borax content. The higher and sooner the peak in the temperature rise curve, the faster the early strength and the quicker the setting could be. The initial setting time of MPC is 40 min at the borax content of 12% and ambient temperature of 25 ℃. The strength at 1.5h increases to 27.2MPa when the elevating curing temperature increases to 50 ℃ for 10 min after casting. It is suggested that increasing of borax content and elevating curing tempera- ture after casting could meet the practical engineering requirements on setting time and early strength of MPC.