The Improvement Of Interfacial Adhesion Between Polyurethane Modified Asphalt And Aggregate

Polyurethane(PU),a new modifier,has been used in asphalt research.However,the poor water resistance of polyurethane modified asphalt(PUMA)pavement is a major concern as it can lead to moisture damage,weaken the bond between asphalt and aggregate,and resulting in other issues to significantly reduce the service life of asphalt pavement.So enhancing the water damage resistance of PUMA through the integration of a silane coupling agent(SCA)has practical significance and value.Adding methods for SCA include a hydrolysate-modified aggregate surface and an integral SCA/PUMA blend.Shear tests were conducted to evaluate the bond strength at the interface between asphalt and aggregate,and the failure mode was determined using image analysis.Internal functional group changes of PUMA due to water treatment were measured using infrared spectroscopy(FTIR),while the distribution of PU particles under water treatment and shear stress were observed by fluorescence microscopy(FM).Scanning electron microscopy(SEM)was utilized to study changes in the surface morphology of aggregates before and after SCA modification.Finally,the effectiveness of SCA addition methods in enhancing interface strength and modification mechanisms was analyzed.The main contents and conclusions are as follows:(1)The optimum PU content in modified asphalt is 20% with a curing time of 1 hour.FM shows that with the increase of PU content,the structure of PU particles is crosslinked.PU particles gradually increase in size over time.After water treatment,the bond strength between PUMA and aggregate decreases significantly,and the failure mode shifts from adhesion to cohesion failure.FTIR reveals that the-CNO group in polyurethane reacted completely,resulting in an increase in the absorption peak area of-C=O,whose peak area positively correlates with bond strength.(2)SCA(KH550)was chosen to modify granite,limestone,and diorite,while JM-PUMA was chosen as the binder.The mass fraction ratio of KH550,ethanol and water is determined to be 1:4:8.Compared to unmodified aggregates,the water damage of modified aggregates and PUMA is reduced.SEM analysis demonstrates that the surface of the aggregates is grafted with a layer of polymer film by SCA,which makes the surface relatively flat.Meanwhile,SCA succeeds in modifying the aggregate surface and forming hydrogen bonds on its surface.PU particle distribution uniforms remain unchanged even with the increase in treatment time.These findings indicate that modifying aggregates with KH550 can improve interface water resistance.(3)The bond strength of the modified KH550/PU composite sample is directly proportional to the KH550 content.Compared to PUMA,the addition of KH550 significantly improves PUMA water resistance.At 35 ℃,the water resistance coefficient of the system increases with SCA content,but decreases over time at 60 ℃.FTIR shows the formation of a new peak(Si-O-Si),indicating that KH550 polymerized in the compound-modified asphalt.Additionally,the reaction of-CNO with amino groups results in an increase in the ester group(-C=O)absorption peak area.The size of PU particles shows slight changes with treatment time,while the network structure remains unaffected by temperature and time,indicating a stable system formed by the interaction between polyurethane and SCA.These results indicate that KH550 can react with polyurethane,which can effectively improve the water damage resistance of modified asphalt.