| Waste tire rubber powder is a kind of modified material with significant economic benefits,which can be used to promote asphalt performance.It has the ability of improving the high-temperature rutting resistance,low-temperature crack resistance,fatigue resistance and reflection crack resistance,reducing the noise,and extending the service life of the asphalt pavement.However,high content rubber powder or ordinary content rubber powder have problems such as easy segregation and construction difficulty.In this paper,by adding disintegrating agent in the preparation process,a disintegrating high content rubber asphalt with low viscosity,uniform stability and good performance isproduced.Its applicable mixture has a wide range of gradation types,a lower asphalt-aggregate ratio than that of ordinary rubber asphalt and excellent road performance,which is beneficial to large-scale popularization and application in engineering.In this paper,the matrix asphalt,rubber powder and disintegrating agent suitable for the preparation of high content rubber asphalt are determined through the comparison and selection of raw materials.Then through the comparison and selection of the preparation process,it is decided that the recommended heating temperature of disintegrating rubber asphalt is 200℃,and the appropriate amount of disintegrating agent is 7.5‰.Through short-term disintegrating tests of rubber asphalt,it is found that the penetration and ductility of disintegrating high content rubber asphalt are proportional to the stirring time,and the softening point and Brookfield viscosity are inversely proportional to the stirring time.The key indexes of disintegrating high content rubber asphalt are initially determined as the penetration at 25℃and the Brookfield viscosity at 135℃.Through long-term disintegrating tests,the correlation analysis between the penetration at 25℃,Brookfield viscosityat 135 ℃and the diameter,the solubility and the softening point difference value at the 48 th hour of the powder of rubber asphalt was carried out,and it was found that the Brookfield viscosity at135℃had a higher correlation with these indexes.Therefore,the Brookfield viscosity at 135℃is used as the best key index for evaluating rubber asphalt.Based on the decay rate of Brookfield viscosity with stirring time,the disintegration of high contentrubber asphalt is divided into three stages:rapid disintegrating stage(stirring for 0-3 hours),stable disintegrating stage(stirring for 3-5 hours)and micro disintegrating stage(stirring for more than 5 hours).The rubber asphalt in the stable disintegrating stage is named stable rubber asphalt,and the disintegrating high content rubber asphalt with 135℃Brookfield viscosity from 1.475Pa?s to2.876Pa?s(stirred for 3 hours)is used as the rubber asphalt popularized in the project.Atdifferent disintegrating stages,the key technical properties,micro morphology,apparent morphology,solubility of rubber powder and the storage stability ofrubber asphalt will show different changes.By analyzing the disintegrating mechanism of high content rubber asphalt,it is found that under the joint action of the pyrolysis reaction of rubber powder and the chemical reaction of rubber powder and matrix asphalt,rubber powder will be disintegrated into carbon black,rubber hydrocarbon rich in olefins,disintegrating gas(A mixture of alkanes and alkenes)and other substances,which will increase the molecular weight and polar component content of disintegrating high content rubber asphalt.By analyzing the rheological properties of the disintegrating high content rubber asphalt,it is found that its high-temperature deformation resistanceis greatly reducedfrom the fast disintegrating stage to the stable disintegrating stage,and its temperature sensitivity,fatigue resistance and low-temperature resistance are significantly improved.When the rubber asphalt enters the stable disintegrating stage,the rheological property of the asphalt changeslittle,so it is reasonable to choose the rubber asphalt with 135℃Brookfield viscosity from 1.475Pa?s to2.876Pa?s(stirred for 3 hours)for popularization and usage.The high-temperature deformation resistance,temperature sensitivity and aging resistance of disintegrating highcontent rubber asphalt are between matrix asphalt and ordinary rubber asphalt,and its fatigue resistance and low-temperature relaxation ability are better than those of matrix asphalt and ordinary rubber asphalt.Through the pavement performance tests of the mixture of disintegratinghigh content rubber asphalt,it is found that the high-temperature rutting resistance ofthe mixture of disintegrating high content rubber asphalt is between those of matrixasphalt mixture and ordinary rubber asphalt mixture,and the low-temperature crack resistance and water stability are better than those of the two asphalt mixtures.Although the most appropriate asphaltaggregate ratio of disintegrating high content rubber asphalt is obviously lower than that of ordinary rubber asphalt,the carbon black in the rubber powder cannot be decomposed due to the large content of rubber powder.Therefore,the asphalt-aggregate ratio of disintegrating high content rubber asphalt is still higher than that of ordinary asphalt mixture. |
