Evaluation And Comparison Research On Performance Of SBS Physical And Chemical Modified Asphalts And Mixtures

To the asphalt pavement of high-grade highways especially of the express way in our country, it is urgent to improve the performance of asphalt binder, the service lever and the using-age of the road because of the increasing traffic flow, heavy-load vehicles and over-loading trucks. Using polymer to modify asphalt has been a valid method and a developing direction to mend the application performance of asphalt. Styrene-Butadiene-Styrene (SBS) modified asphalt has been popular used and deeply studied worldwide because of its extraordinary performance.What about the performances of onsite and commercial SBS modified asphalts and mixtures? There are no overall evaluation and comparison in the nation. After reviewing, analyzing and summarizing the relevant former research results, this study conducted numerous experiments to lucubrate the performances of SBS physical and chemical modified asphalts and mixtures. The data and the production of the research contribute significantly to the theory development and the practical application of SBS modified asphalt.This paper summarized the theoretical researches, the actual state of application and the progresses of the polymer modified asphalt internal and external. It also documented the methods of choosing the modifier, the technical standard and evaluating indicator of the modified asphalt and mixture.Based on the analysis of the structure of SBS modified asphalt, the right SBS and matrix asphalt were selected to make compatible modified asphalt by appropriate technics. Then the technical performances of various SBS modified asphalts were studied. It indicates that the content of SBS is good correlated with the performance indexes. It also concludes that the ideal content of SBS is 4.5%~5.5%. The SBS particles and the asphalt micelle could constitute a perfect structure.Based on the comparison of the assessment method of polymer modified asphalt from both national and abroad, the research adopted the conventional, unconventional and SHRP testing methods to evaluate the SBS modified asphalts and mixtures, then the data were analyzed and compared. The result shows that the SBS chemical modified asphalt is better than the physical one in terms of the high-temperature stability, aging resistance and stability. The low temperature performance and the anti-fatigue performance of the former are appreciably better than the latter. Their elastic recovery performance and workability are equivalent. The result also shows that the mixture using SBS chemical modified asphalt is better than the one using the physical modified asphalt. The former is appreciably better than the latter in terms of the low temperature stability or the anti-fatigue performance. Their water stabilities have no difference. It shows that the corresponding performances of SBS modified asphalts and mixtures are accordant.Emphatically, FDT was utilized to observe low temperature drawing performance of SBS modified asphalt. The effects of some factors were evaluated, such as the property of matrix asphalt, the kind and content of polymer, thermal ageing, and the low temperature performance.Fluorescence optical microscopy was adopted to analyze phase state structure and microscopicconstitution of SBS physical and chemical modified asphalt. It concludes that SBS is the dispersed phase and the asphalt is the continuous phase in the SBS physical modified asphalt, which constitute a " sea—island" structure. However SBS and asphalt constitute a two continuous phase structure in the chemical one. It is one of the reasons that the SBS chemical modified asphalt has premium properties. Regression analysis proves that the microstructure and service property have good correlation.This paper used modern analysis technology to study the mix mechanism of SBS modified asphalt. They were IR, DSC, and NMR. The analysis of IR and NMR concludes that the spectrograms of SBS modified asphalt are the superposing of the SBS spectrogram and asphalt spectrogram. It shows that there are no chemical reaction between SBS and asphalt. The DSC spectrogram of SBS chemical modified asphalt is flatter than the physical one, and its absorption peak is smaller than another one. It also indicates that the thermal stability of the former is better than the latter. The conclusion validates the macroscopical results.After indoor testing, the research checked and measured the service performance of SBS physical and medical modified asphalt by constructing test-road. The results show that the application performances of both asphalts meet or exceed the engineering discipline's demands. Because of the lack of enough operation time, it will need to be checked periodically and evaluated synthetically under the presence of long term traffic load and climate in the future research.