Technical Research On Application Of Polyurethane Recycled Aggregate In Pavement Base

In order to find a new way to apply pavement recycled aggregates in the drainage base,try to overcome the shortcomings of long construction period and easy cracking of semi-rigid pavement base.In this paper,the permeable polyurethane stabilized recycled aggregate?PPSRA?were studied by raw material property test,comparison test of key design parameters,mechanical properties test of mixture and road performance test,it can provide reference for the application of PPSRA in the drainage pavement baseFirstly,the content of the micropowder,water content,apparent density,crushing value,needle and plate particle content and properties of polyurethane adhesive of cement stabilized macadam recycled coarse aggregate were determined.The influence of micropowder on the bond force of polyurethane adhesive was determined by shear strength test.The influence of the water content of the recycled aggregate on the adhesive bond force of the polyurethane stabilized recycled aggregate was determined by the cantabro scattering test.The results showed that the content of the micropowder of the recycled coarse aggregate after washing was significantly smaller than that of the original recycled coarse aggregate.The bond force of polyurethane adhesive decreases with the increase of micropowder content.The mass of the scattered loss of the polyurethane stabilized recycled aggregate increases rapidly when the water content of the recycled coarse aggregate is greater than 2%.And the apparent density,crushing value,needle and plate particle content of the recycled coarse aggregate meets the requirements of the secondary and below road pavement base.The initial setting time of the polyurethane adhesive is 2h,and the final setting time is 24h.The unmixed adhesive leaks into the air for a long time,which will cause a lot of bubbles after the adhesive condenses and has a great influence on the shear strength of the adhesiveSecondly,in order to effectively control the structure of the permeable polyurethane stabilized recycled aggregate,the volume method is used on mix design of the PPSRA,and researching the key parameters.Determination of gradation of aggregates with open-graded asphalt mixture.Determine the range of the stone than range from 3%to 5%with the cantabro scattering test and the leakage test.The hardness test,shear strength test and stability test of polyurethane adhesive are used to determine the influence of the composition ratio of the adhesive,the stone than and the porosity on the PPSRA.It is found that the hardness of the polyurethane adhesive decreases with the decrease of the ratio of the component of the polyurethane adhesive,and the shear strength and stability reach a peak when the ratio of the composition ratio of the polyurethane adhesive is 1:2.5,so it is judged that the optimum composition ratio of the polyurethane adhesive is 1:2.5.Then from the Marshall stability test,the compressive and flexural strength tests,the best stone than was found to be 4%.Then,through the unconfined compression test,the image of the test specimen after the test was processed by ImageJ image processing software,and the damage position,crack development trend and damage cause of the polyurethane recycled aggregate were studied.From the test results,most of the cracks are in the middle of the test piece.The development trend of the failure position and crack of the test piece under the vertical load will be affected by the insufficient stone than.From the shape of the failure surface,the damage of the test piece is mostly caused by the low strength of the recycled aggregate.Finally,the strength,water stability,erosion resistance and drainage performance of polyurethane stabilized recycled aggregates were analyzed by unconfined compression test,water immersion Marshall test and freeze-thaw split test,anti-scour test and water seepage test.The test results show that the compressive resilient modulus of the mixture was concentrated in2000³000MPa,and the residual stability of the mixture reaches a peak when the stone than is4%.At this time,the water stability is the best.The polyurethane has a small loss of scouring quality and a large loss of strength.The water permeability coefficient satisfies the requirement that the drainage coefficient of the drainage pavement is not less than 0.35 cm·s^-1.