Research On Low Temperature Toughening Method Of Rubber-Asphalt And Its Mixture

Scrap rubber is a non-degradable polymer material.Using crumb rubber made from scrap tires to modify asphalt can improve the thermostability,crack resistance at low temperatures,ageing resistance,fatigue resistance,and other properties of asphalt.Proper use of crumb rubber can alleviate the adverse impact of scrap tires on the environment.Low consumption of asphalt is a significant economic advantage of rubber asphalt.Besides,rubber asphalt features various remarkable properties,especially its crack resistance at low temperatures.Compared to styrene-butadiene-styrene(SBS)modified asphalt,rubber asphalt has much lower stiffness at low temperatures and thus can make pavements more resistant to cracking at low temperatures.Unlike in the United States and other developed countries,rubber asphalt is still in the initial stage of technical development in China.However,rubber asphalt can make the pavement of a high-load road more susceptible to rutting and other thermal damage than SBS modified asphalt,due to its poorer high-temperature performance.This disadvantage of rubber asphalt offsets its absolute advantage in resistance to cold cracking,obstructing promotion of rubber asphalt.Therefore,research is urgently needed to find new approaches to making full use of rubber asphalt and discover more advantageous properties.In this study,order to highlight the low temperature properties,Shell’s 90#bitumen,the matrix asphalt,was mixed with different amounts(18%、20%、22%、24%)of crumb rubber of different particle sizes(20、40、60 mush)to prepare rubber asphalt.Then laboratory tests were carried out to investigate how the amount and particle size of crumb rubber affected the SHRP performance indicators and basic technical indicators of the prepared rubber asphalt,and focuses on the impact of low-temperature toughness.This paper calculated the compounding ratio(power size is 60 mesh counts with 22%mixture)of low temperature toughening rubber based on a further analysis of its performance pattern in low temperature with Burgers model combined with the its viscoelasticity parameter,relaxation and delaying time as well as experiment statistics.Based on the mechanism of modification,with the rubber asphalt of 60 mesh counts and 22%mixture as an object of study,this paper researched on the impact of additive,ranging from Sasobit,a warm-mix addictive,USP,a rubber modifier to naphthenic oil,an industrial filler,on the low temperature toughness of rubber asphalt.Combined with SHRP performance indicators and basic technical indicators,adherence and the data from Burgers model,this paper discovered that 8%naphthenic oil would yield the best result.The gradation of mineral aggregate was selected using the Marshall volume index and the optimal asphalt to aggregate ratios for ZRARHM-13(w)and ARHM-13(w)were determined by a Marshall test.Then a water immersion test,small beam bending test at low temperatures,and rutting test at 60 ℃ were conducted on the two types of mixtures with optimal asphalt to aggregate ratios to analyze their economic efficiency.According to the results of the analysis,ZRARHM-13(w)exhibited a 10.5%rise in unit cost,a 83.9%increase in low-temperature performance and a 17.2%decrease in high-temperature performance compared to ARHM-13(w),while other performance indicators varied slightly between them.This suggests that ZRARHM-13(w)has a higher economic efficiency and ZRAR(containing 22%crumb rubber and 8%naphthenic oil)can be used as the binder of asphalt pavement to significantly improve the low temperature cracking performance of pavement,while other road use performance can be guaranteed.