Study On The Performance Of Polyvinyl Alcohol Fiber Reinforced Cement Stabilized Granite Crushed Stone Base

In order to reduce the pollution of the surrounding environment and reduce the project cost,the granite cave slag from tunnel excavation is used in the cement stabilized gravel base course of highway,and the polyvinyl alcohol fiber is mixed into the mixture to overcome the defects of poor shrinkage resistance,crack resistance and fatigue durability of cement stabilized gravel base course mixture in general.In this study,the engineering properties of the aggregates obtained from the crushed sesame white granite cave slag were first tested in conjunction with the pavement subgrade project of Liubin Expressway in Guangxi,and the virtual packing density of the four preliminary grades was obtained according to the compressible packing model theory,and the correlation between the changes of the virtual packing density on the maximum dry density and 7d unconfined compressive strength was investigated,and the optimum grade was selected with the 7d unconfined compressive strength as the index.Then,the optimum gradation was selected under the optimal gradation.Then,under the optimal gradation,the influence law of polyvinyl alcohol fiber on the performance of cement stabilized granite crushed stone base mix was analyzed by three aspects of mechanical properties,shrinkage properties and fatigue properties.Firstly,according to the results of mechanical properties and shrinkage performance tests after polyvinyl alcohol fiber is incorporated into cementstabilized granite subgrade mix,the effect of fiber dosing on the mechanical properties and shrinkage performance of cement-stabilized granite subgrade mix is investigated,and the optimum polyvinyl alcohol fiber dosing of the mix is determined.Bending fatigue and splitting fatigue were used to conduct fatigue tests,and the effects of the test methods on the fatigue test results of cement stabilized granite crushed stone base were compared and analyzed.The fatigue performance of the mixes with and without the optimum polyvinyl alcohol fiber admixture was compared by using bending fatigue as the test method.Weibull distribution model was used to analyze the fatigue test data and establish the indoor fatigue equation of cement stabilized granite crushed stone base mix.The results of the study showed that:(1)5-10 mm and 10-20 mm granite coarse aggregates play a dominant role in the virtual density of cement stabilized granite crushed stone base mix,and the maximum dry density and unconfined compressive strength of the mix are influenced by the gradation and cement dosage.(2)Different doses of polyvinyl alcohol fiber can improve the mechanical properties of cement stabilized granite crushed stone mix,among which the unconfined compressive strength,bending tensile strength and splitting strength reach the peak when the fiber dose is 0.06%;the uniaxial compression modulus reaches the peak when the fiber dose is0.09%.(3)Polyvinyl alcohol fiber can improve the shrinkage performance of cementstabilized granite aggregates,and the dry shrinkage strain is the smallest at 0.03% fiber dosing;the temperature shrinkage strain is the smallest at 0.09% fiber dosing.(4)Weibull distribution model can well characterize the fatigue life of cement stabilized granite crushed stone base mix.Compared with the splitting fatigue test method,the fatigue performance of the bending fatigue method decays faster and is more sensitive to stress changes as the stress ratio gradually increases.(5)The comprehensive road performance of cement stabilized gravel base is the best when the amount of polyvinyl alcohol fiber is 0.06%.And in this amount,the fiber can effectively improve the problem of fatigue cracking damage when the stress is high.In this study,the sesame white granite tunnel slag is reasonably applied to the cement stabilized gravel subgrade of highway,which has good economic and environmental benefits and can provide reference for similar projects.