Study On Self-healing Properties Of Cement Stabilized Macadam After Early Microcracking

The shrinkage stress of cement stabilized macadam can be reduced through the micro-cracks caused by early microcracking,which can effectively prevent or reduce the shrinkage cracking of road base.In the later period of curing,the micro-cracks were gradually healed or even recovered relying on the self-healing properties of cement stabilized macadam,so it would not have a serious impact on the bearing capacity of pavement structure.Hence,the quantitative characterization of cement stabilized macadam self-healing process after microcracking,and the proficiency in the changing rule of cement stabilized macadam healing properties under different factors are the focus of the paper.On the basis of discussing the mechanism of cement stabilized macadam after early microcracking,the mechanical characteristics,mesoscopic structural characteristics and durability of cement stabilized macadam during the healing process was studied.This paper has completed the following contents:(1)On the basis of discussing the shrinkage cracking regularity of semi-rigid base,the mechanism of microcracking to reduce the shrinkage cracking was studied,and then the microcracking of cement stabilized macadam was simulated according to the indoor shrinkage test,thus the critical point that the shrinkage stress is just less than the tensile strength of material was determined,simultaneously demonstrated the effectiveness of microcracking to reduce the shrinkage stress of semi-rigid base.(2)By introducing the concept of microcracking degree to characterize the change of material properties of cement stabilized macadam after early microcracking,it is expressed as the decrease percentage of compression rebound modulus.The reasonable control of microcracking degree is the key of producing the ideal micro-cracks after microcracking.In order to achieve the effective control of microcracking process,the microcracking degree control model considering the coupling conditions of microcracking load,microcracking time and material characteristics was established based on response surface methodology.(3)Through the test of unconfined compressive strength,splitting strength and compression rebound modulus,the self-healing process and the mechanical strength changing rule of cement stabilized macadam after early microracking were systematically studied,then the effects of different microcracking time and microcracking degree on the healing properties were obtained using the nonlinear fitting,and the critical state of healing degree was obtained from the perspective of material healing.(4)Using digital explicit crack width monitor KON-FK(B)to detect the micro-cracks width,and then the representative values of micro-cracks width under different working conditions and the change rule of representative values were obtained based on the descriptive statistics of SPSS.Next,use stereo microscope XTZ-05 T to image the healing product,and the coverage rate of healing product to micro-cracks was acquired by image segmentation technology,so the healing process of cement stabilized macadam after early microcracking can be quantitatively characterized through the coverage rate,and the analysis of micro-cracks healing characteristics was achieved from the perspective of meso structure.