Study On Properties And Mechanism Of Waste Rubber Modified Cement Stabilized Macadam

At present,cement stabilized macadam is the most widely used semi-rigid base material in China,it has the advantages of good integrity,wide source of raw materials and low cost,but there are also some defects,which are easy to produce cracks and affect the normal use of the road.In order to eliminate the cracks of cement stabilized macadam base,according to the method of replacing stone chips in aggregate gradation with rubber powder,the waste rubber powder is mixed into cement stabilized macadam,the mechanical properties,fatigue properties,deformation properties and mechanism characterization of cement stabilized macadam with different rubber powder content were studied.The mechanical properties of cement stabilized macadam with different rubber powder content were tested by unconfined compressive strength,compressive resilient modulus and flexural tensile strength tests,when the cement dosage is 5%,the mechanical properties of cement stabilized macadam decrease with the increase of rubber powder content.MTS810 testing machine was used to test the fatigue life of cement stabilized macadam with different rubber powder content,and the fatigue equation was calculated by the least square method.The results show that the fatigue life of cement stabilized macadam decreases with the increase of stress ratio when the rubber powder content is the same;The least square method is used to calculate the fatigue equation,and the regression coefficients a and B are compared.After adding rubber powder,the fatigue performance of cement stabilized macadam is improved,the higher the rubber powder content,the better the fatigue performance of cement stabilized macadam.The effects of different rubber powder content on the dry shrinkage of cement stabilized macadam were studied by dry shrinkage test and mercury intrusion test,and the influence mechanism of waste rubber powder on the dry shrinkage of cement stabilized macadam was characterized.The results show that the dry shrinkage strain of cement stabilized macadam decreases with the addition of rubber powder;the maximum dry shrinkage strain of standard cement stabilized macadam is 7.7×10^-5;the maximum dry shrinkage strains of cement stabilized macadam with rubber powder content of 10kg/m³,20kg/m³and 30 kg/m³are 6.1×10^-5,4.9×10^-5and 4.9×10^-5,respectively,which are 79%,63%and 60%of the benchmark cement stabilized macadam.The most probable pore size of cement stabilized macadam mixed with rubber powder increases,and the pore size distribution curve is tooth shaped;the pore size distribution curve of standard cement stabilized macadam is relatively smooth;the most probable pore size of cement stabilized macadam with 20 kg/m³and 30 kg/m³rubber powder is larger than that of cement stabilized macadam with 10 kg/m³rubber powder.In the range and age of the test,rubber powder can reduce the dry shrinkage strain of cement stabilized macadam,and its effect is related to the amount of rubber powder.The effect of rubber powder on the thermal shrinkage of cement stabilized macadam was studied by means of temperature shrinkage and stress-strain tests.The results show that the average temperature shrinkage coefficient of cement stabilized macadam decreases with the increase of rubber powder content,When the rubber powder content is 10 kg/m³,the average temperature shrinkage coefficient is 90%of the reference cement stabilized macadam.When the rubber powder content is 20 kg/m³and 30 kg/m³,the average temperature shrinkage coefficient is 69%and 24%of the reference cement stabilized macadam,respectively;the temperature stress of the rubber cement stabilized macadam is less than that of the standard cement stabilized macadam.Because the rubber powder has a high energy absorption capacity,it can absorb the stress produced by the mixture and reduce the temperature shrinkage coefficient.