Abstract:

To prepare the crumb rubber-modified asphalt (CRMA) is an effective way to recycle waste rubber and reduce environmental pollution.In order to investigate the physical and chemical behaviors of the crumb rubber in asphalt and its modification on asphalt,CRMAs were prepared respectively under the conditions of different powder dosages,temperatures and treatment time.Then,the particle size of the crumb rubber,which had been separated from asphalt by means of the elution method,was measured by using an optical microscope,and the volume expan- sion rate was proposed to characterize the volume change of the crumb rubber in asphalt.Besides,the IR and DSC tests were conducted on the asphalt samples in which the crumb rubber had been removed by means of the sieve method.The results indicate that (1) swelling and degradation are the two important factors influencing the volume of the crumb rubber in the process of preparing CRMAs,and the volume expansion rate first increases and then de- creases with the increases of the crumb rubber dosage and the preparation temperature as well as the extension of the treatment time; (2) after the swelling,the molecular chains of the rubber rupture and release small molecule materials,and the materials dissolve into asphalt and play a role of asphalt modification,which causes the absorp- tion peaks of typical functional groups to significantly increase; and (3) strong endothermic peaks appear in the DSC curves of the asphalt samples prepared under the conditions of 195℃,1. 5h and 175℃,3. 0h,which means that such processing conditions as too high temperature and too long time may lead to the excessive degradation or aggregation of the crumb rubber as well as the asphalt aging,thus changing the physical and chemical states of the CRMAs and degrading their performances.From the perspective of the swelling and degradation of the crumb ru- bber,it is suggested that the crumb rubber dosage and the processing time should respectively be 20% approxi- mately and less than 1. 5h,and that the preparation temperature should not be higher than 195℃.

Key words: crumb rubber-modified asphalt, swelling, degradation, volume expansion rate, infrared spectra ana- lysis, differential scanning calorimetry