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.
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.
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.
China’s highway construction has moved from “construction-oriented” to the development stage of “equal attention to construction and maintenance”. The infrastructure represented by urban expressways, under heavy and complex traffic loads, is prone to a variety of diseases that take place in the middle and lower layers of pavement such as “frost boils” and “voids”, which cannot be repaired ideally with the help of conventional detection and treatment techniques. In order to solve the above problems, this paper adopts nondestructive testing plans such as ground penetrating radar and falling weight deflectometer to conduct multidimensional rapid detection of the road surface to obtain the image information and mechanical data of the road structure. Based on the improved calculation method, the pavement disease area, depth and type can be effectively judged. Combined with the observation of water level, the polymer grouting reinforcement plan is designed to eliminate the problems in the middle and lower layers of the road surface. It can effectively reduce the incidence of diseases in the upper layer of the sidewalk, and significantly improve the efficiency and service level of the sidewalk.
The internal structure of semi-flexible pavement (SFP) is prone to fatigue damage, which affects its service life. The cement mortar admixture has a crucial influence on the fatigue resistance of SFP. In order to explore and study the fatigue resistance performance of SFP, Waterborne Epoxy Resin, emulsified asphalt and Carboxyl Latex were selected as cement mortar admixtures to prepare special cement mortar, and the effect of admixtures on the fatigue resistance of SFP was evaluated by indirect tensile fatigue test. The tests show that Waterborne Epoxy Resin undermines the fatigue resistance of SFP, while emulsified asphalt and Carboxyl Latex can improve it.
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