Study On PVA Fiber Cement Stabilized Macadam Base Material And Structure Performance

As the main semi-rigid base course of motorways in China,the cement stabilized macadam has high strength and good integrity but poor resistance.The cracking in the base layer reflects to the road surface,leading easily to the early fatigue failure of the pavement structure.The PVA fiber of high elasticity and modulus is incorporated into the cement stabilized macadam to improve the pavement performance of cement stabilized macadam base.The effects of PVA fiber content and PVA fiber length on mechanical and fatigue properties of cement stabilized macadam were analyzed by indoor splitting test,dynamic elastic modulus and splitting fatigue test.The grey relational analysis theory was used to obtain the evaluation index of crack resistance of cement stabilized macadam with PVA fiber and the fatigue cumulative damage theory to estimate the cumulative fatigue damage.This paper comprehensively studied the PVA fiber cement stabilized crushed stone base material and its structural performance and conclusions can be drawn as following:The results of splitting test showed that the splitting strength of PVA fiber cement stabilized macadam increases with the increase of cement content;when the cement content of cement stabilized grindstone was fixed,the PVA fiber mass content was 0.9kg/m3.When the PVA fiber length was 24 mm,the splitting strength of the PVA fiber cement stabilized macadam was the maximum.Dynamic elastic modulus test results showed that when the amount of cement is fixed and the PVA fiber content is 0.9 kg/m3 with the PVA fiber length 24 mm,the dynamic elastic modulus of the PVA fiber cement stabilized macadam is the maximum.Grey relational theory gave the evaluation indexes of crack resistance of PVA fiber cement stabilized macadam,namely dry shrinkage energy crack resistance coefficient and temperature shrinkage energy crack resistance coefficient.The effect of cement content and PVA fiber length on the crack resistance of PVA fiber cement stabilized macadam was analyzed.The results showed that when the PVA fiber content was 0.9kg/m3 and PVA fiber length was 24 mm,the energy consumption coefficient of dry shrinkage of PVA fiber cement stabilized macadam increased by 100%,122% and 73.5% respectively and the energy consumption coefficient of PVA fiber cement stabilized macadam increased by 54.2%,55.2% and 75.9 respectively,both compared with ordinary cement stabilized macadam.Thus,the incorporation of PVA fibers can significantly enhance the crack resistance of cement stabilized macadam.Cleavage fatigue test results showed that PVA fiber can significantly improve the fatigue properties of cement stabilized macadam materials.Based on the actual fatigue data of fatigue tests,the stress-strain fatigue equations of ordinary and PVA fiber cement-stabilized macadam were obtained.Similarly,based on the fatigue test data processed with Weibull distribution,the stress-strain fatigue equations of ordinary and PVA fiber cement-stabilized macadam with different guaranteed rates were obtained.The stress fatigue equation obtained from the actual indoor test data was modified to obtain the fatigue life prediction fatigue equation of ordinary and PVA fiber cement stabilized macadam base.Based on Miner's cumulative fatigue damage theory,with the temperature distribution interval and axle load distribution of II climate zone in Yunnan Province as background,the cumulative fatigue damage of the general cement stabilized macadam base,the PVA fiber cement stabilized macadam base and the asphalt pavement base layer under the total axle load of 15 years design life was analyzed to predict the fatigue life of the base layer.The analysis results showed that the incorporation of PVA fiber can increase the fatigue life of the cement stabilized crushed stone base by 2.06 times.