Research And Application Of Fabricated Magnesium Phosphate Concrete Pavement

Assembled pavement is an economical pavement structure form and has advantages of short construction period.At the same time,the assembled pavement can solve the problems of salt erosion of cement concrete pavement and slippage,rutting and cracking of asphalt concrete pavement under the action of high temperature and heavy load.At present,the materials for assembled pavement are ordinary cement concrete,which has the problems of long maintenance time and late traffic opening.With the characteristics of short setting time,high early strength and good abrasion resistance of magnesium phosphate cement,the application of magnesium phosphate cement concrete to the assembled pavement can realize the quick production of the assembled pavement and rapid paving,which improve the pavement paving efficiency and realize the quick open traffic.But the rapid hydration reaction leads the setting time is short,which cause a series problem in construction application.This research firstly combines the research of retarding materials of magnesium phosphate cement,selects phase change materials with better retarding effect to compound,and formulates high-efficiency composite retarder that has obvious regulation on setting time and little influence on strength under low dosage conditions,so that magnesium phosphate concrete has sufficient pouring time for application on assembled pavement.For the road mix ratio of magnesium phosphate concrete,the response surface method is applied to simulate the early strength of magnesium phosphate cement concrete with different mix ratios,and the mix ratio of assembled magnesium phosphate concrete with different strength levels is optimized.In order to further improve the feasibility of applying magnesium phosphate concrete to the fabricated pavement blocks,the experimental research on water resistance,corrosion resistance,frost resistance and wear resistance was carried out,and the durability analysis was carried out through macroscopic phenomena combined with microscopic scanning.To apply magnesium phosphate concrete to the fabricated composite pavement,the following test research and analysis are carried out:Combining with hydration and retarding mechanism of magnesium phosphate cement,high-efficient setting material was selected from existing phase change materials of retarding material and compounded to obtain composite retarder CR,which effectively prolongs setting time of magnesium phosphate cement at low dosage.The effect of composite magnesium phosphate cement retarder CR on properties,micro-morphology and solid phase composition of magnesium phosphate cement was studied,and the mechanism of CR regulating setting time of magnesium phosphate cement was explored.Based on the response surface method,the mix proportion of magnesium phosphate concrete is designed and optimized.A prediction model between four factors(M/P,W/C,G/C,Fiber)and compressive strength and flexural tensile strength is established.The model is tested by variance analysis and significance analysis.The results show that the response surface model can effectively and accurately predict the early performance.The order of significance of the four factors on the compressive strength of magnesium phosphate concrete is W/C>M/P>G/C>Fiber,and W/C and M/P are the dominant factors affecting the early strength.The mix proportion of magnesium phosphate concrete with C30-C50 strength grade was determined according to the performance test of optimized mix proportion by response surface method.According to the requirements of quick repairing of assembled pavement,the comprehensive performance research on optimized mix ratio is carried out,including water resistance,erosion resistance,freezing resistance,and micro performance characterization.Results show that the application of optimized proportion magnesium phosphate cement concrete in pavement will obtain better durability,and reveal that the water resistance of magnesium phosphate concrete is closely related to its mix ratio.Finally,the prefabricated magnesium phosphate cement concrete pavement is prepared,the campus test pavement is repaired.The test shows that the optimized proportion of magnesium phosphate cement concrete has good durability,and can meet the requirements of quick repair construction of cement concrete pavement.The research provides reference and basis for quick paving repair and large-scale application of assembled pavement.