Study On Preparation And Rheological Properties Of Rubber Composite Modified Asphalt In Wide Temperature Range

In recent years,with the growth of the number of motor vehicles in China,the problem of solid waste pollution caused by the generation of waste tires has become increasingly serious.How to efficiently treat and apply waste tires has become an important engineering topic,which is closely related to practical production.Rubber asphalt is a green and environmentally friendly asphalt material with excellent performance,but there are significant physical and chemical differences between rubber powder and asphalt.The compatibility between the two is poor,and the modified asphalt is modified with rubber powder alone.The temperature range of its modified asphalt is narrow,especially during the storage process,where the rubber powder degrades at high temperature,resulting in a faster decay of its high-temperature grade.In view of this,this paper aims to improve the PG(Performance Grade)grading range of rubber asphalt.With the help of external additives,the preparation and performance research of high-performance rubber composite modified asphalt with a PG grade of PG88-22 or PG94-22 in a wide temperature range are carried out,serving the research and application of high-performance environmentally friendly asphalt materials.Firstly,the preparation of modified asphalt with wide temperature range rubber composite was studied.This article used the asphalt performance improver HPT(product obtained from hydroxylation of ethylene stearic acid amide),SBS(styrene butadiene styrene triblock copolymer),and CR(waste tire rubber powder)independently developed by the laboratory to prepare modified asphalt,and determined the optimal preparation plan based on the conventional performance of modified asphalt.Research has shown that the larger the dosage of HPT modifier,the smaller the proportion of light components in asphalt,and the harder and more brittle the modified asphalt.While losing some low-temperature performance,the high-temperature performance also increases.When the HPT modifier content is 1%,the softening point and 5 ℃ ductility of CR-SBS-HPTMA(rubber powder/SBS/HPT composite modified asphalt)can maintain a high level.At this time,the modified asphalt has good high-temperature and low-temperature performance,and the difference in the 48 h segregation softening point is small,with good thermal storage stability.When the HPT modifier content is greater than 1%,the penetration value of the modified asphalt begins to decrease,and the Brinell viscosity begins to significantly increase,indicating that the asphalt properties begin to harden and thicken,Not suitable for construction.In order to maintain the optimal temperature sensitive performance and construction workability of modified asphalt while also considering economic and environmental benefits,the dosage of HPT modifier is selected as 1% of the mass of the base asphalt.Secondly,fluorescence microscopy was used to analyze the microstructural differences between the wide temperature range rubber composite modified asphalt and the control sample.The results show that there is mutual crosslinking between CRs in various rubber composite modified asphalt,forming a certain structure,and the CR particles in the asphalt samples are significantly reduced after short-term and long-term aging.After the addition of HPT modifier,the agglomeration phenomenon between asphalt powder is reduced,and the distribution of CR particles is more fine,indicating that the addition of HPT promotes the light components in asphalt to enter CR,allowing CR to swell better.In the fluorescence microscope photos of CR-SBS-HPTMA with optimized HPT dosage,it was found that CR particles and SBS particles were uniformly distributed within the asphalt,and some SBS and CR were crosslinked into anchor points,resulting in the entire system being fixed as a strip network.Finally,the selected rubber powder/SBS/HPT composite modified asphalt(CR-SBS-HPTMA),rubber powder modified asphalt(CRMA),rubber powder/SBS composite modified asphalt(CR-SBSMA),and rubber powder/HPT composite modified asphalt(CR-HPTMA)were used for temperature scanning test,frequency scanning test,MSCR test,time scanning test,and bending beam rheological test,respectively.The temperature scanning test at high temperatures found that the high-temperature rutting resistance of asphalt decreases with increasing temperature,and the rutting factor of CR-HPTMA is better than that of CRMA.This indicates that the addition of HPT improves the high-temperature performance of asphalt and enhances its rutting resistance.In the frequency scanning test,as the temperature increased from 50 ℃ to 80 ℃,the complex shear modulus of CR-SBS-HPTMA gradually exceeded CR-HPTMA to become the highest value,indicating that CR-SBS-HPTMA can maintain a higher elastic ratio compared to CR-HPTMA at higher temperatures.The intermediate temperature rheological properties of modified asphalt were studied through time scanning experiments at 25 ℃.The results showed that HPT and SBS had a certain improvement in the fatigue life of CRMA at high stress levels,but it was not as significant as at low stress levels.In the bending beam rheological test,the asphalt sample meets S<300MPa and m>0.3 at-12 ℃,which is PG-22 grade.The PG low-temperature grade of CRMA,CR-SBSMA,CR-HPTMA,and CR-SBS-HPTMA is PG-22 grade.