In this paper, a high-performance geopolymer grouting material based on slag and fly ash was developed and the properties were investigated. The fluidity, setting time, compressive strength, water resistance and drying shrinkage were studied to evaluate the workability and mechanical properties of geopolymer grouting material (GGM). X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to analyze the microstructural performance of GGM. The results show that the concentration of alkaline activator and slag content plays a significant role in properties of GGM and the optimum formula has been obtained. In the course of the study, the effect of concentration of alkaline activator and the content of slag on the workability and mechanical performance of GGM is different. All properties of geopolymer were considered comprehensively, the slag content and concentration of alkaline activator were 70% and 37%, which indicated that the geopolymer grouting material made from slag and fly ash could meet the requirements of concrete reinforcement well and was friendly to the environment.

Porous asphalt mixture is a type of asphalt mixture with good drainage. However, it has poor tensile strength performance and durability. Chopped basalt fibers (CBF) have been proved to be an effective additive to improve the mechanical and fatigue performance of asphalt mixtures, but little attention has been paid on porous asphalt mixture. This paper examined the effect of chopped basalt fibers with different lengths (nonfiber, 3 mm, 6 mm, 9 mm, and 12 mm) and contents (3% and 4%) on the performance of the porous asphalt mixture. A series of tests were conducted to figure out the optimum fiber length and content, including draindown test, cantabro abrasion test, freeze-thaw split tensile test, wheel tracking test, low-temperature cracking resistance test, and four-point bending beam test. Thereafter, indirect tensile tests at different temperatures were conducted to investigate the tensile strength properties of porous asphalt mixtures with optimum fiber length and content. Besides, the macroscopic and microscopic morphology of fracture sections of the samples after indirect tensile tests were studied by using a single-lens reflex (SLR) camera and scanning electron microscopy (SEM) so as to further explore the reinforced mechanism of chopped basalt fibers. The results show that the addition of chopped basalt fibers can generally improve the performance of porous asphalt mixture since chopped basalt fibers form a three-dimensional network structure in the porous asphalt mixture.

Two kinds of rubber modified asphalts were investigated and compared with virgin asphalt. In order to get closer to engineering practice, different combinations of four environmental factors were merged into the laboratory aging simulation. Subsequently, conventional property tests, including softening point, viscosity, creep stiffness, creep rate, and fatigue cracking were conducted on asphalt samples. The performance difference of asphalt before and after aging was selected as an evaluation index for asphalt aging degree. The results indicate that two kinds of rubber modified asphalts show stronger resistant ability to temperature deformation and better resistance to traffic loading than virgin asphalt in all kinds of environmental factors combinations. Tests on chemical analyses were conducted to investigate the asphalt aging characteristics. The apparent morphology of rubber modified asphalts are described in detail under an environment scanning electron microscope (ESEM). The damage condition reflected in images reveals the aging degree caused by multiple environmental factors. Moreover, the thermogravimetric analysis (TG) confirms that three kinds of asphalts can maintain thermal stability in various environments. Additionally, new characteristic functional groups were not detected in the infrared (IR) spectra of rubber modified asphalts, which means they have stable antioxidant properties given that their oxidation degrees change slightly throughout the aging processes.

Adding basalt fiber (BF) can effectively enhance the performance of asphalt mixtures and improve the service quality of asphalt pavement. However, the effect of BF on the high-temperature performance of different types of asphalt mixtures and systematic high-temperature performance test analysis are still not well known. To address this issue, three typical types of asphalt mixtures of AC-13, SMA-13, and SUP-13 were selected. Wheel tracking test, uniaxial penetration test, dynamic modulus test, and dynamic creep test were conducted. In addition, relevant parameters of dynamic stability, penetration strength, dynamic modulus index, and flow number were analyzed. The results showed that adding BF into the asphalt mixture could improve the dynamic stability, penetration strength, dynamic modulus index, and flow number significantly, indicating that adding basalt fiber is an effective solution to the rutting deformation damage of asphalt pavement. Moreover, the parameter of dynamic stability presented an approximate polynomial correlation with penetration strength, dynamic modulus index, and flow number, respectively. These findings provide a certain theoretical reference for evaluating the high-temperature performance of BF-modified asphalt mixtures.

Non-renewable resources such as natural stone and asphalt are in short supply. Recycling technology, with its lower cost, has been used as the primary approach to asphalt pavement maintenance engineering. The inclusion of reclaimed asphalt pavement materials in producing new asphalt pavements may increase the risk of cracking. The strength and toughness of the asphalt mixture can be reduced. In this study, Hamburg wheel tracking tests (HWTT) were performed on rejuvenated asphalt mixtures with distinct maintenance processes. Different kinds of fibers have been used as additives to reinforce the rejuvenated asphalt mixtures. The HWTT rutting curve was identified as having three stages, including the post-compaction stage, the creep stage, and the stripping stage. The three-stage rutting curve model was used to determine the intersection point between the creep stage and stripping stage. The other two feature points (i.e., the post-compaction point and the stripping inflection point) were redefined with a new calculation method. Then, the rutting effect and stripping effect were separated with these feature points. The performance and economic benefits of fiber-reinforced rejuvenated asphalt mixtures were investigated through grey correlation analysis under the three maintenance processes. The feature points of the HWTT curve and the cost of the corresponding maintenance process were selected as the impact factors. Finally, the optimal scheme was developed by analyzing the influence of each factor on both performance and economic benefits.

The bond strength between basalt fibers and asphalt binders is an important parameter that can be used to evaluate the influence of basalt fibers on the mechanical properties of asphalt binders and asphalt mixtures. To date, however, there remains a lack of methods that can be used to assess the bond strength between basalt fibers and asphalt binders. This study employed a fiber-asphalt pull-out tester (POT). Significant upward, peak, and downward stages were observed from the relationship curves between the pull-out force (POF) and displacement, corresponding to the holding stage and reaching the maximum POF stage and the sliding or failure stage between fibers and asphalt binders. Maximum POF is recommended to calculate the bond strength between basalt fibers and asphalt binders. The types of asphalt binders suitable for basalt fibers and the appropriate fiber embedding depths for different types of asphalt binders guiding the selection of fiber length are recommended based on the influence of fiber embedding depth and asphalt binders on the fiber–asphalt bond strength. In addition, surface energy was used to calculate the bond strength as well. Surface energy was determined from contact angle measurements using the sessile drop method. Furthermore, a scanning electron microscope (SEM) was employed to examine the bond mechanism between asphalt binders and basalt fibers. These experiments showed how basalt fibers serve to reinforce asphalt mixtures by bonding with asphalt binders.