负温环境下复合磷酸盐对磷酸镁水泥性能的影响

The effect of composite phosphates on the properties of magnesium phosphate cement under negative temperature environment

川藏线海拔较高,大部分地区受冰雪灾害影响,混凝土道路易遭受损伤,对修补材料提出了更高的要求。针对严寒环境适应较好的磷酸镁水泥(MPC)存在低温下强度发展较慢的问题,探究了在负温(-5℃)环境下,磷酸二氢钾和磷酸二氢钠复合加入对MPC强度、水化特性、微观结构的影响。结果表明,复合掺加磷酸二氢钠可以显著提高MPC的强度,3 h抗压强度达到了41.2 MPa,相比于纯磷酸二氢钾组提高了776.6%,28 d抗压强度可达70.0 MPa以上。磷酸二氢钠的加入可促进新的水化产物生成,即Na-Struvite,该水化产物多为无定形或针状,可以有效填充孔隙,细化孔径,有利于强度的提高。

The Sichuan-Tibet Highway has high altitudes,and most areas are affected by snow and ice disasters,causing varying degrees of damage to concrete roads,which also poses higher requirements for repair materials.Currently,magnesium phosphate cement(MPC),which adapts well to cold environments,faces the issue of slow strength development at low temperatures.This experiment mainly investigates the effects of the combined addition of potassium dihydrogen phosphate and sodium dihydrogen phosphate on the strength,hydration characteristics,and microstructure of magnesium phosphate cement under sub-zero temperatures(-5℃).The results show that the addition of sodium dihydrogen phosphate can significantly improve the strength of magnesium phosphate cement.When fully added,the compressive strength at 3 hours reached 41.2 MPa,which is a 776.6%increase compared to the pure potassium dihydrogen phosphate component of MPC,and the 28-day strength can exceed 70.0 MPa.The addition of sodium dihydrogen phosphate can promote the formation of new hydration products,namely Na-Struvite,which are mostly amorphous or needle-shaped.These hydration products can effectively fill the pores,refine the pore size,and contribute to the increase in strength.