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The compatibility between waste plastic polymers and bitumen is the most challenging issue hindering the improvement of modified bitumen performance. The current practice of recycled waste plastics includes the use of polyvinyl chloride (PVC), polypropylene (PP), polyethylene (PE), etc. This study was designed to investigate the compatibility of different waste plastic polymers with bitumen binders by conducting molecular dynamics (MD) simulations at different temperatures. The molecular models of these materials were constructed in this study for the compatibility analysis, and they include the base bitumen, polymers (PVC, PP, and PE), polymer- bitumen blending systems. Using the output and related calculations of these MD models, the properties of these blending systems were measured at different temperatures through the calculation of the solubility parameter (δ) and interaction energies. The compatibility analysis is discussed in the context of these simulation results. The simulation results for the solubility parameters and interaction energies show consistent trends. The results showed that PVC and PP had better compatibility with bitumen at 433.15 K and that PE and bitumen had good compatibility at 393.15 K. Moreover, it can be deduced that the order of compatibility of the three polymers with bitumen is as follows: PVC > PE > PP. In addition, these research results can be referenced for the industry and research development of modified bitumen. [ABSTRACT FROM AUTHOR]

The compaction quality of asphalt surface courses has a significant impact on the overall performance of asphalt pavements, but the dynamic response and compaction degree variations of different asphalt surface courses (top, middle, and bottom surface courses) during vibrational compaction have still received limited research. SmartRock sensors can be utilized to monitor aggregate acceleration in real-time. This study aims to address this gap using SmartRock sensor technology to further understand the compaction mechanisms of different asphalt surface courses from a particle perspective, as well as the relationship between aggregate acceleration and compaction degree. The results indicate that the rolling of steel drums induces a significant alteration of the aggregate acceleration along the roller's rolling direction, primarily resulting in horizontal shearing in that direction. As distance increases, vibration waves gradually attenuate on both sides of vibrating drums, and surface course thickness and gradation significantly affect acceleration amplitude. There is a linear correlation between triaxial aggregate acceleration and compaction degree, with the vertical correlation being the strongest. Finally, an empirical relationship between triaxial acceleration and pavement compaction degree was established, providing a basis for predicting the asphalt surface course density. These findings enhance our understanding of pavement compaction mechanisms and promote innovation in asphalt pavement compaction and quality control methods. [ABSTRACT FROM AUTHOR]

There are several influencing factors in the preparation of MK (metakaolin)-GGBS (ground granulated blast furnace slag)-based geopolymer repair mortars, including the MK-GGBS ratio, the alkalinity of the alkali activator solution, the modulus of the alkali activator solution, and the water-to-solid ratio. There are interactions between these factors, such as the different alkaline and modulus requirements of MK and GGBS, the interaction between the alkaline and modulus of the alkali activator solution, and the influence of water throughout the process. The effect of these interactions on the geopolymer repair mortar is not fully understood, making optimization of the MK-GGBS repair mortar ratio difficult. Therefore, in this paper, the response surface methodology (RSM) was used to optimize the preparation of the repair mortar, with GGBS content, SiO2/Na2O molar ratio, Na2O/binder ratio, and water/binder ratio as influencing factors and 1 d compressive strength, 1 d flexural strength, and 1 d bond strength as evaluation indices. Additionally, the repair mortar's overall performance was assessed in terms of setting time, long-term compressive and bond strength, shrinkage, water absorption, and efflorescence. The results show that RSM was successful in establishing a relationship between the repair mortar's properties and the factors. The recommended values of the GGBS content, Na2O/binder ratio, SiO2/Na2O molar ratio, and water/binder ratio are 60%, 10.1%, 1.19, and 0.41, respectively. The optimized mortar meets the standard's requirements for set time, water absorption, shrinkage values, and mechanical strength, with minimal visual efflorescence. The back-scattered electron (BSE) images and energy dispersive spectroscopy (EDS) analysis show that the geopolymer and cement have good interfacial adhesion, and a denser interfacial transition zone exists in the optimized proportion. [ABSTRACT FROM AUTHOR]