Research On Crack Development Law Of Cement Stabilized Macadam Base

Cement stabilized macadam basic and asphalt mixture surface layer are the majority of high grade highway structure form. The shrinkage phenomenon of water stabilized gravel base itself result in base cracking which would reflected back to the surface layer and caused pavement cracking, then the service life of the road comfort is deeply effected. The primary exploration of the crack is to monitor the crack development law, and to propose the method to reduce the crack. In this paper, by using the distributed optical fiber monitoring strain theory, we carried out the feasibility analysis of fiber optic monitoring base crack, the law of the development of crack in the base,and the crack control study. The research results lay the foundation for the research of the basic crack and the reduction of the primary cracking. The main contents of this paper are as follows:First, the research on crack resistance of cement stabilized macadam base is carried out,including the research of the method of reducing the drying shrinkage coefficient, temperature shrinkage coefficient, and the grading optimization of the basic by adding steel fiber and expansive agent MgO.Then, the feasibility analysis of the crack is carried out by using indoor and outdoor test.Research on the accurate and effective monitoring method of primary crack, including the design,layout and construction of the sensor network for crack monitoring, as well as the layout of conventional measurement facilities.In the end, we studied the cause of the cracks and the main influencing factors, the cement stabilized macadam base crack development, including the time, crack position, development trend etc. We considered the environmental factors including the seasonal, temperature, precipitation, and so on. And the influence of different construction methods(Three layer continuous paving method,two layer continuous paving method) and field curing condition on the crack development law of cement stabilized crushed stone base are studied. We established theoretical model of the cracking of cement stabilized crushed stone base.The research conclusions show that fiber optic monitoring has high accuracy, and the design of basic crack monitoring method has high survival rate. The main reason for the cracking of the basic level is that the dry shrinkage stress concentration is higher than that of the base. After cracking, it changes with the change of water content and temperature. The construction method and field curing conditions can affect the cracking of the basic level, and the reasonable construction method and fieldcuring conditions can reduce the cracks. The expansive agent MgO and steel fiber can reduce cracking,optimized gradation can improve the base crack resistance.