Reinforcement Effect of Different Fibers on Asphalt Mastic

Fiber materials as an asphalt mixture additive and stabilizer can effectively improve the performance index of asphalt pavement. In this study, lignin and carbon fiber were used as modifiers to study their effects on the road performance of asphalt mastic. Based on the frequency sweep, linear amplitude sweep (LAS) and multi-stress creep recovery (MSCR) experiments were conducted to test the high-temperature rutting and medium-temperature fatigue resistance of asphalt mastic with different fiber incorporation and low-temperature performance tests based on bending beam rheometer (BBR). The results indicate that adding fibers increased the stiffness of the asphalt mastic, and the modification effect of lignin fibers was better than that of carbon fibers. Meanwhile, the characteristic flow index of the asphalt mastic gradually increased with the increase in temperature, indicating that it gradually became a near-Newtonian fluid at higher temperatures. The addition of fibers also improved the high temperature rutting resistance of the asphalt mastic but did not have an advantageous effect on fatigue and low temperature cracking resistance. Additionally, the fitting results of the four-parameter Burgers model show that the use of fiber modification decreases the proportion of elasticity and viscous creep compliance but increases the delayed elasticity part.

Comparative Life Cycle Assessment of Asphalt Mixtures Using Composite Admixtures of Lignin and Glass Fibers

Lignin and glass fiber were used as additives to improve the quality of road pavements and minimize moisture damage and cracking at low temperatures on asphalt pavement, according to a previous laboratory study. The aim of this paper is to make a significant contribution to the environmental assessment of the construction of road pavements using four types of asphalt mixtures based on the life cycle assessment (LCA) methodology according to the requirements of ISO 14040, considering the impact of raw material extraction, asphalt mixture manufacturing, transportation, and wearing surface construction. The results of the environmental assessment showed that all studied asphalt mixtures do not offer any improvement in all impact categories, and three modified asphalt mixtures have a slight negative effect in all impact categories. The composite mixture has the highest negative effect of the studied three modified asphalt mixtures in all categories except in the marine aquatic ecotoxicity potential category and freshwater aquatic ecotoxicity potential category, where the lignin modified asphalt mixture has the highest negative effect in these two categories but has the best environmental impacts on most of other impact categories. Furthermore, the negative effect caused by composite asphalt mixtures is minimal and thus can be used to improve the overall performance of asphalt pavement.

Physical, Rheological, and Morphological Properties of Asphalt Reinforced by Basalt Fiber and Lignin Fiber

Studies show that each kind of fiber has its own advantages in improving the properties of asphalt binders. However, there are very limited research studies about mixed fiber-reinforced asphalt (MFRA). In this study, two kinds of fibers, basalt fiber (BF) and lignin fiber (LF), were selected to reinforce SBS (styrene–butadiene–styrene triblock copolymer)-modified asphalt, which is now widely used in pavement engineering. MFRA samples with different fiber mix ratios (FMRs) were prepared for the tests of softening point, ductility, and rheological properties, the micromorphology of which was studied by using scanning electron microscope (SEM). The oil (asphalt) absorption rates of mixed fibers with different FMRs were also tested. The results show that the properties of MFRA were affected by the physical and chemical properties of fibers. Basalt fiber can better strengthen the physical properties of MFRA, while lignin fiber is good for improving the rheological properties, and the oil absorption rate of lignin fiber is higher than that of basalt fiber. Furthermore, the best FMR calculated by the efficacy coefficient method (ECM) was recommended as 1:2 (BF:LF). An interface layer between the fiber and asphalt was observed from the micro images, proving that the fibers bond well with the asphalt. Generally, mixing BF and LF together into SBS-modified asphalt could make full use of the advantages of different fibers and reinforce the comprehensive performance of MFRA better.

Evaluation of the Properties of Asphalt Mixes Modified with Diatomite and Lignin Fiber: A Review

Due to rapid growth of traffic density, the phenomenon of overloading on high-grade highways causes various modes of distresses to the pavement such as rutting, thermal cracking, and water damage. Modification of asphalt mixes is the most common solution to improve the performance of asphalt pavement to mitigate its damages. This paper provides a review on the influence of diatomite or lignin fiber as a modifier in asphalt mixes. In order to assess the effectiveness of selected additives on asphalt mix performance, several tests, such as wheel tracking, indirect tensile, three points bending, freeze thaw splitting, and marshall immersion, were reviewed. The review indicated that the addition of diatomite increases the high temperature rutting resistance of asphalt mixes, but some researchers observed that it has a little improvement on the low temperature performance of asphalt mixes and the optimum amount of diatomite at 12–14% of asphalt binder can be added into the mix. In contrast, lignin fiber has a significant effect on the low temperature cracking resistance of asphalt mixes; however, its influence on the high temperature rutting resistance of asphalt mix is limited, and the optimum amount of lignin fiber is 0.2–0.4% per asphalt mix composition. The review also indicated that the single additives haven’t the ability to enhance the overall performance of asphalt mix. Consequently, the utilization of double additives can improve the overall performance of asphalt mixes at the same time, but it is still in an early stage in the application of highway engineering due to all previous researches concentrated on the single modification. Moreover, this review suggests that the future use of diatomite and lignin fiber compound modified asphalt mix can improve the overall mix performance.