The effect of composite phosphates on the properties of magnesium phosphate cement under negative temperature environment
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 ce-ment(MPC),which adapts well to cold environments,faces the issue of slow strength development at low temperatures.This experi-ment 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 phos-phate 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.
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