Evaluation On The Rheological Performance Of Hydraulic Bitumen Binders And Its Concrete Of Impermeable Layer Under High And Low Temperatures

Because of the excellent anti-seepage and deformation properties,hydraulicrolled asphalt concrete anti-seepage facing is an important form of anti-seepage structure for pumped storage reservoirs.Hydraulic asphalt concrete of impermeable layer has long service life and high durability requirements.In order to ensure the safety and durability of hydraulic engineering,more stringent technical requirements were put forward for hydraulic bitumen binders than high quality road bitumen binders.Hydraulic bitumen binders as the key cementing material of hydraulic asphalt concrete,it’s directly determines the performance of impermeable layer.Therefore,customized processing of hydraulic bitumen binders were required according to the characteristics of the projects.Because the crude oil and processing techniques used for hydraulic bitumen are currently experiencing a fundamental change in China,the application of polymer-modified bitumen is becoming the trend for pumped storage power stations.Polymer-modified bitumen will be more promising when dealing with extremely low and high temperatures.The current performance evaluation of hydraulic bitumen binders is mainly based on three indexes,which makes the correlation between bitumen and concrete performance poor,and can not truly reflect the properties of hydraulic bitumen binders.As a result,the rheological properties of the hydraulic bitumen binders and the high and low temperature performance of asphalt concrete in impermeable layer were studies.The performance correlation between hydraulic bitumen binders and its concrete was established,which can provide a reference for the establishment of hydraulic bitumen binders optimization and asphalt concrete material composition optimization and performance regulation.The high and low-temperature performance of five hydraulic bitumen binders was evaluated using the dynamic shear rheometer(DSR)test,infrared spectrum test and direct tensile(DT)test.These hydraulic bitumen binders were respectively applied for several pumped storage power station projects that were constructed or under construction.At the same time,the mix design was carried out,and the slope flow and low temperature three bending test were carried out on the hydraulic asphalt mixture.The influence of gradation index,bitumen-aggregate ratio and aggregate particle shape on the high and low temperature performance was studied.And the correlation analysis between the performance of hydraulic bitumen binders and the performance of hydraulic asphalt mixture was established.It is found that the DSR rheological master curves can well distinguish the difference of each bitumen binder as well as the effect of polymer modification.Phase angle master curves,black diagrams and infrared spectra all indicated that several penetration-grade hydraulic bitumen binders were not virgin bitumen binders but were modified with relatively lower SBS polymer content when compared with traditional SBS-modified bitumen.When selecting the commonly used Karamay SG70 hydraulic bitumen as a reference,the normal SBS-modified bitumen was superior to other bitumen in terms of low-and high-temperature performance.Several slightly SBS-modified bitumen binders did not always show consistent results,which indicated that slightly modified bitumen may not really have the desired performance as expected.Therefore,SBS-modified bitumen will be more promising when dealing with extremely low or high temperatures.The influence of rheological properties of hydraulic bitumen binders on high and low temperature properties of hydraulic asphalt mixture was studied by preparing different hydraulic asphalt concrete specimens.The test results indicated decreasing the content of bitumen and increasing the gradation index can improve the anti-slope flow performance of asphalt concrete.The sensitivity of asphalt concrete to bitumenaggregate ratio varies greatly with different gradation indexes.The aggregate particle shape has a significant effect on the anti-slope flow performance of asphalt concrete.The angularity and sphericity of aggregate can be measured by aggregate image measurement system.And the aggregate with high angularity and low sphericity was beneficial to improve the anti-slope flow performance.The low temperature flexibility of hydraulic asphalt concrete of impermeable layer has a good positive correlation with the content of bitumen binders.The selection of higher bitumen aggregate ratio and lower gradation index was beneficial to improve the low temperature flexibility,reduce the variability and improve workability.Bitumen performance was well compared with the mixture performance by using the bitumen creep,relaxation and tensile failure strain corresponding to the asphalt concrete slope flow,the maximum bending strain and the failure temperature,respectively.Compared with the traditional penetration,softening point and ductility test,it indicated that the DSR rheological test,creep test,direct tensile test and stress relaxation test can be used as more powerful tools for the characterization and optimization of hydraulic bitumen binders.Finally,by establishing the correlation between the rheological properties of hydraulic bitumen binders and the performance of hydraulic asphalt concrete,it is found that the complex modulus and phase angle of hydraulic bitumen binders are strongly correlated with the performance of hydraulic asphalt concrete regardless of high or low temperature.In addition,the non-recoverable compliance of hydraulic bitumen binders has a strong correlation with slope flow,and the direct tensile strain,stiffness modulus and residual relaxation modulus of hydraulic bitumen binders have a great correlation with low temperature flexibility and crack resistance of hydraulic asphalt concrete.Therefore,in addition to the three traditional indexes,the complex modulus,phase angle,non-recoverable compliance,direct tensile strain,stiffness modulus and residual relaxation modulus of hydraulic bitumen binders at the corresponding service temperature should also be considered when selecting the raw material of hydraulic bitumen binders to further check its performance.In this study,the difference of rheological properties of different hydraulic bitumen binders and its influence on the performance of asphalt concrete of impermeable layer were analyzed,and the correlation between rheological properties of hydraulic bitumen binders and the actual service performance of asphalt concrete of impermeable layer was established.The key control indexes of performance for the preparation of hydraulic bitumen binders and asphalt concrete of impermeable layer were put forward to realize the material composition optimization design and performance control of asphalt mixture of impermeable layer based on bitumen binders optimization.