Research On Anti-cracking Performance Of Cement Stabilized Crushed Stone Material Mixed With Expansion Agent In Northern Hebei Region

Since the reform and opening up,with the rapid development of my country’s economy,most of the highway base materials in our country are semi-rigid base materials.It has many advantages,but it also has its own shortcomings.Asphalt pavements in northern Hebei have cracked and damaged,the temperature shrinkage and cracking of semi-rigid base materials is the main cause of damage.In this paper,starting from improving the anti-cracking performance of cement stabilized macadam with expansion agent,the gradation design,road performance and shrinkage performance of cement stabilized macadam with expansion agent are studied and analyzed.The main contents are summarized as follows:1.Investigate and analyze the cracking problem of the asphalt pavement of Beijing-Tibet Expressway(K164+000～K179+0000),and collect the distribution of pavement cracks: 19.2 cracks per 100 m on the upward road,and 19.2 cracks per100 m on the downward road.There are 9.7 cracks,and the number of cracks is much larger than the design value of asphalt pavement.2.Perform mechanical performance test and frost resistance test for cement stabilized macadam with expansion agent and cement stabilized macadam without expansion agent,including unconfined compressive strength test,indirect tensile test,compression and resilience test Quantity test and freeze-thaw test: Adding expansion agent can improve the mechanical properties and frost resistance of the base material.3.The effect of expansion agent on its shrinkage performance was studied,and dry shrinkage test and temperature shrinkage test were carried out.The shrinkage test shows that the replacement amount of expansion agent is inversely related to the shrinkage coefficient.The cumulative dry shrinkage strain and water loss rate in the first 5 days are relatively large,so controlling the initial water content of the base material can reduce the shrinkage deformation of the material;the temperature shrinkage test shows that the effect of adding an expansion agent on the temperature shrinkage coefficient of the material is obvious.The temperature shrinkage strain is more sensitive to the low temperature environment(below 0°C).4.Study the law of shrinkage crack formation of semi-rigid base materials.Using mathematical modeling methods,while considering the effects of material drying shrinkage and temperature shrinkage,an approximate calculation formula for shrinkage stress in the base material is analyzed and deduced.Combined with the shrinkage performance test data of this paper,the recommended value of the pre-saw gap of the base material is given.Experimental studies have shown that adding expansion agents can reduce the shrinkage of cement stabilized crushed stones and increase the crack resistance of base materials,thereby improving the service life of the road surface and driving comfort.