Experimental Study On High Performance Grouting Material For Semi-flexible Pavement

Semi-flexible pavement is widely used in high-speed toll stations,intersections and other road sections.In order to ensure the durability,early strength and adaptability of semi-flexible pavement in cold climate,a suitable grouting material is needed to meet the requirements of semi-flexible pavement.High performance grouting material for semi-flexible pavement is a grouting material that can provide higher early strength,greater fluidity and adapt to cold conditions.Based on the ratio of sulphoaluminate cement to ordinary portland cement,the mixed cement with the characteristics of both early strength of sulphoaluminate cement and high later strength of ordinary portland cement is studied,and the basic ratio is determined according to the test results: sand-cement ratio 0.3,water-cement ratio 0.44,sulphoaluminate cement:ordinary portland cement = 7: 3.Through the single mixing test and orthogonal test of mineral admixtures,it is found that silica fume has the greatest effect on improving the early strength and microbeads have the greatest effect on improving the fluidity.Orthogonal test results show that adding 6% silica fume,9% microbeads and 3% fly ash to semi-flexible pavement has the greatest improvement.Adding a certain amount of gypsum can not only play a greater retarding role,but also improve certain early strength,solve some shrinkage problems,and determine the gypsum content to be 10%.Water reducing agent with early strength function is prepared and mixed into high-performance grouting material for semi-flexible pavement.After that,the optimal dosage and proportion of retarder are found through single-mixed three retarders and double-mixed tests.Finally,lithium carbonate and rubber powder are found through single-mixed tests to determine each component.The optimum ratio of high-performance grouting material for semi-flexible pavement is determined through experimental optimization as follows: sand-cement ratio 0.30,water-cement ratio 0.44,sulphoaluminate cement: ordinary portland cement,=,7: 3,silica fume 6%,microbeads 9%,fly ash 3%,gypsum content 10%,retarder 0.15%,boric acid: borax6: 4,lithium carbonate 0.08%,rubber powder 2%,and a certain amount of PC-L early strength polycarboxylate superplasticizer.In order to adapt to the low temperature environment in winter,the orthogonal test of cellulose ether and three kinds of antifreeze agents was carried out.The results show that the addition of cellulose ether greatly improves the water retention performance,and the best choice of antifreeze agent is sodium nitrite.