In recent years, preventive maintenance has been used widely to solve the problem of early-stage asphalt pavement damage. However, conventional preventive maintenance treatments cannot effectively prevent rutting or damage resulting from the leakage of diesel fuel to the pavement. In this context, numerical simulations of uniaxial penetration tests were conducted with the Discrete Element Model to evaluate the feasibility and effectiveness of pavement surface solidification with a special seal coat. Standard viscosity tests on mixtures of waterborne epoxy resin and emulsified asphalt used as the Permeating and Solidifying Seal Coat (PSSC) material were performed, and uniaxial penetration tests and accelerated loading tests were conducted on asphalt mixture specimens with and without the PSSC. The optimum proportion of PSSC material was determined and its permeability, rutting resistance, diesel fuel corrosion resistance, and durability were evaluated. The results of this study indicate that the superficially solidified pavement with PSSC can effectively enhance rutting resistance and diesel fuel corrosion resistance and can provide more durable skid resistance and better antistripping performance than conventional preventive maintenance treatments. Therefore, the PSSC could be considered a new generation of preventive maintenance treatments for asphalt pavements.
Semiflexible mixture is a composite paving material combining the advantages of both asphalt and cement concrete materials. It consists of matrix asphalt skeleton and cement mortar. Due to the different volume characters between asphalt structure and cement mortar, stress concentration always happens in this semiflexible mixture, leading to internal cracking. The objective of this study is to alleviate the internal cracking concern of the semiflexible mixture by adjusting the material components. To this end, optimal material design and numerical simulation have been conducted. Matrix asphalt structures with four different air voids were incorporated with different dosages of cement mortar. The contraction strain and expansion strain of cement mortar as well as the indirect tensile strength of matrix asphalt structure were measured. The results were input into ABAQUS for numerical simulation. The results indicated that (1) the internal stress in this semiflexible mixture is mainly determined by the contraction of cement mortar, rather than expansion; (2) larger air void of matrix asphalt structure and less volumetric variation of cement mortar reduce the internal stress; (3) once the air void of matrix asphalt structure is decided, both maximum contraction and expansion deformations of cement mortar should meet specific requirement to ensure less internal cracking. This is a practical-ready paper that provides reference for the anticracking design of semiflexible pavement.
The anti-slip (AS) layer of the cement concrete pavement (CCP) can probability decrease traffic accidents and extend the service life of the road. Epoxy resin has excellent adhesion and mechanical strength, making it possible in this field. Herein, a flexible waterborne epoxy resin (WER) without a small molecule emulsifier was synthesized by bisphenol A epoxy resin, poly (propylene glycol) diglycidyl ether (PDE), diethylenetriamine (DETA). The mechanism of the group reaction was characterized by fourier transform infrared (FTIR), and dynamic scanning calorimetry (DSC) determined the heat of curing of WER. Then, the physical properties of WER were enhanced by the silane coupling agent modified nano-silica (SCA-NS) and the composite's water absorption rate and mechanical propriety were evaluated. Finally, the pavement performance of the AS layer was prepared and tested as well as compared with the commercial waterborne epoxy resin (CWER) and emulsified asphalt (EA). The result shows EA has low durability and adhesion strength than epoxy resin. The small molecule emulsifier and low-flexible resistance of CWER decrease water stability and antisliding durability of the AS layer. Due to applied nanomaterial reinforced and without small molecule emulsifiers, the WER base AS layer shows extremely high adhesion strength, water stability, and skidresistance durability at addition 3 wt% of SCA-NS, which have a great potential for CCP.
The current understanding of the influence of smoke suppressants on the smoke inhibition effect and working performance of different types of asphalt is limited. In this study, portable gas detector (PGD) tests were used to investigate the influence of the smoke suppressant on different types of asphalt and the smoke purification effect. Subsequently, gas chromatography-mass spectrometry (GC-MS) was used to analyze the influence of the smoke suppressant on the volatile organic compounds (VOCs) in different types of asphalt fume, so as to compare and verify the PGD tests results. Finally, scanning electron microscopy and energy dispersive spectrometry were used to observe and analyze the influence of the smoke suppressant on the microstructure and element composition of different types of asphalt. The results show that the smoke suppressant can purify various harmful gases volatilized from different types of asphalt, but the effect and the optimal dosage of smoke suppressant are slightly different. The purification rate of the smoke suppressant for SO2 or H2S in the fumes of various asphalts can reach >70% and the NO and VOC purification rates can reach >40%. The influence of the smoke suppressant on the VOC purification rate of different asphalts detected through the GC-MS and PGD tests is similar. The smoke suppressant has little effect on the asphalt surface microstructure and on the changes in the element content in asphalt, indicating that it has no effect on the main properties of the asphalt itself. This study is helpful to further understand the relationship between smoke suppressants and the smoke inhibition effect and the working performance of different types of asphalt. Additionally, it provides basis and guidance for the development of low-smoke asphalt with a better emission reduction effect, which has a certain guiding and application significance.
This paper mainly used the Superpave and the Marshall design methods to design the mix ratio of the hot mix plant recycled asphalt mixture. The road performance of AC-20, SUP-20 with 30% RAP content and AC-20 with 50% RAP content was studied to evaluate the water stability and high temperature stability and low temperature crack resistance of the recycled asphalt mixture. Research shows that the road performance of AC-20 mixed with 50% RAP content meets the technical requirements of the same type of asphalt mixture. It is recommended to use the Marshall design method for hot mix plant recycled asphalt mixture design.
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