Granular lateritic soil is commonly used for road construction in humid tropical and subtropical regions. However, the high plastic clay content and poor particle distribution of some laterite materials make them unsuitable for bases and subbases. Lime treatment is a widely used method for improving problematic lateritic soil, and liquid ionic stabilizers are considered an environmentally friendly solution for reinforcing such soils. However, using only lime or only stabilizers may not be optimal. This study investigated the effect of treating granular lateritic soil with hydrated lime and a new liquid stabilizer, Zhonglu-2A (ZL-2A). A series of indoor tests, including compaction, California bearing ratio, and unconfined compressive strength tests, were conducted to evaluate the effects of hydrated lime content and stabilizer content on the mechanical properties, mineralogical composition, and microstructure of the soil. The results show that an increase in hydrated lime dosage increases the optimal moisture content and decreases the maximum dry density. The CBR of lime-stabilizer-treated laterite was at least 2–3 times higher than that of the only-lime-treated soil. The highest CBR was observed in samples treated with 0.2‰ ZL-2A stabilizer. The sample with 6% lime and 0.2‰ ZL-2A stabilizer exhibited the highest unconfined compressive strength, and a nearly linear increase was observed between the unconfined compressive strength and CBR. Further investigation of the stabilization mechanism using X-ray diffraction mineralogy analysis and scanning electron microscopy revealed that the inorganic substances of the ZL-2A stabilizer and the hydrated lime provided the basic conditions for the reaction and generated cementitious hydrates on the clay particles. The mixture of granular lateritic soil and hydrated lime was wrapped by the ZL-2A stabilizer, forming a complex spatial structure and improving the strength of the soil. To improve the bearing capacity of subgrades in actual subgrade engineering, a combination of a liquid ionic stabilizer and lime should be used to treat laterite.

Serious environmental pollution will occur if corn stalk materials are discarded randomly or burned in open air. This study presents a possible method for using corn stalk materials to make fibers used in stone matrix asphalt (SMA) mixtures to address this problem. To obtain an in-depth understanding of the application of corn stalk fibers in SMA mixtures, basic properties such as high-temperature, low-temperature, moisture susceptibility, and fatigue performance, and the dynamic modulus were researched. The performances of SMA mixtures with lignin fibers and basalt fibers were studied as comparative research. Corn stalk fibers and basalt fibers, used as composite fibers, were incorporated jointly into the SMA mixtures, and the performance was evaluated. The test results showed that the high-temperature, low-temperature, and moisture susceptibility performance of SMA mixtures with corn stalk fibers can meet the specification requirements. The addition of corn stalk fibers and basalt fibers in SMA mixtures improved the high-temperature, low-temperature, and fatigue performance of SMA mixtures and had comparable dynamic moduli. A content of 0.6% corn stalk fibers is recommended for SMA mixtures. For the application of composite fibers, contents of 0.4% corn stalk fibers and 0.2% basalt fibers currently are recommended for SMA mixtures. In general, corn stalk fibers can be used in asphalt pavement, and the application of corn stalk fibers can reduce construction costs and environmental pollution.

Corn stalk fibers are produced by physical and chemical means. To prove that corn stalk fibers can adsorb asphalt, the adsorption process of asphaltenes was studied. There are four main components in asphalt, and this study used asphaltenes as an adsorbate in an asphalt solution. The corn stalk fibers were characterized by scanning electron microscopy and Brunauer-Emmett-Teller (BET) analysis, which indicated that the corn stalk fibers were composed of macroporous and mesoporous structures, with uneven surfaces. The amount of asphaltenes adsorption was found to increase with the weight of the corn stalk fiber, the initial concentration of asphaltenes and the adsorption time. The asphaltene adsorption gradually slowed with time. The Redlich-Peterson model can describe the adsorption process better than the Freundlich and Langmuir models. The pseudo-second-order model presented better suitability for adsorption equilibrium data than the pseudo-first-order model. The adsorption process can be separated into three parts: film diffusion, both film diffusion and intraparticle diffusion, and intraparticle diffusion through the Weber and Morris model. The Boyd model found that film diffusion is the rate-limiting step. The high-temperature performance of corn stalk fiber asphalt increased with increasing mass ratio of fibers and increasing asphaltene adsorption rate. Finally, the corn stalk fibers were proven to adsorb the asphalt effectively.

Generally, the dynamic modulus and bending stiffness modulus are used to evaluate the mechanical properties of asphalt mixture, and they are also used as basic parameters for asphalt mixture design. Therefore, a study was conducted on changes in the dynamic modulus and bending stiffness modulus of hot-recycled asphalt mixture with high levels of reclaimed asphalt pavement (RAP) under the influence of different factors: dosage of regenerant, curing temperature, and curing time. The performance of reclaimed asphalt pavement (RAP) was first evaluated. Then, the hot-recycled asphalt mixture was adjusted and designed in order to conduct modulus experiments, composed of the dynamic modulus test and three-point bending test. Finally, the influencing factors were not only qualitatively but also quantitatively analyzed to clarify the change laws of the mechanical parameters of hot-recycled asphalt mixture. The results showed that the modulus of the recycled asphalt mixture first decreased, then increased, and then decreased with increasing dosage of regenerant. As the curing time or temperature increased, the modulus first decreased and then increased. In terms of the dynamic modulus of the hot-recycled asphalt mixture, the curing time had the greatest impact, followed by dosage of the regenerant and curing temperature. For bending stiffness modulus, the influence of dosage of the regenerant was the greatest, followed by curing time and curing temperature. For the bending stiffness modulus of hot-recycled asphalt mixture, the curing conditions had a greater influence compared with the dynamic modulus.

This study, based on 90# matrix asphalt binder, investigates the use of SBS, C9 petroleum resin, and polyethylene (PE) as modifiers to prepare high-viscosity modified asphalt binders. Using the uniform design method, the modifier proportions were optimized to meet engineering requirements for high viscosity. The effects of modifier dosages on asphalt binder properties, including penetration, ductility, softening point, and dynamic viscosity, were systematically analyzed, and a multivariate nonlinear regression model was constructed to determine the optimal proportioning. Subsequently, the aging resistance and high-temperature performance of the modified asphalt binders were evaluated through short-term aging tests and rheological property tests. The results show that SBS and PE have a significant positive impact on penetration and softening point, while C9 petroleum resin mainly enhances ductility. The synergistic effect of SBS and PE significantly improves dynamic viscosity. Under the optimal proportioning (SBS 7.5%, C9 petroleum resin 6.0%, PE 5.0%), the high-viscosity modified asphalt binders meet technical standards for key performance indicators. The short-term aging test reveals an elastic recovery ratio exceeding 95%. Rheological performance testing indicates that the modified asphalt binders exhibit excellent rutting resistance and temperature adaptability under high-temperature conditions.

Reliable traffic load characterization remains a critical challenge in many African countries due to the lack of continuous field measurements. This study developed an integrated dynamic traffic monitoring and weigh-in-motion system on representative highways in Kenya to obtain long-term, multi-source traffic data. Traffic operations were quantified across hourly, weekly, and monthly scales, including flow variability, vehicle class composition, axle loads, overload behavior, and speed distributions. Results indicate that the spatiotemporal characteristics of traffic volume show pronounced short-term fluctuations but strong long-term stability. Despite their lower proportion, multi-axle heavy trucks dominate structural loading, with overload ratios exceeding 80% and gross weights approaching 100 t. Over 60% of vehicles operate at medium-to-low speeds (20–60 km/h), extending load duration and increasing pavement damage potential. These combined effects indicate that average indicators alone underestimate true loading demand. The proposed framework provides field-based traffic load spectra and a transferable methodology for traffic monitoring and pavement design optimization across developing regions in Africa.