High-modulus asphalt mixtures (HMAM) have been widely used in asphalt pavement in high-temperature areas of China, owing to their advantages in rutting and fatigue resistance. However, moisture and temperature interdependently determine the degradation of pavement performance of the HMAM, owing to the unique climatic conditions in summer in some high-temperature areas of China. There were few studies on the rutting and fatigue properties of the HMAM under the combined action of moisture contents and temperatures. Hence, the moisture absorption characteristics of the HMAM at different temperatures were analyzed. The rutting performance of the HMAM was investigated under different moisture contents and temperatures. The fatigue performance of the HMAM was investigated under different moisture contents, temperatures, and stress levels. Results show that: the rutting and fatigue resistance of the HMAM decrease with the increase in temperature and moisture content. The dynamic stability decreases by 8.9% at 40 °C and by 7.0% at 60 °C on average per 10% increase in moisture content and decreases by 22.7% on average per 10 °C increase in temperature. The fatigue life decreases by 4.1% at 15 °C and by 3.1% at 40 °C on average per 10% increase in moisture content and decreases by 31.3% on average per 10 °C increase in temperature. Finally, a prediction equation was established to predict the fatigue life under different moisture contents and temperatures.

The reinforced concrete invariably involves some diseases (e.g., crack, void, etc.) due to the complex service conditions. These diseases are usually repaired to extend the service life of reinforced concrete by using cement grouting materials. In order to meet a certain color need of reinforced concrete, toner is mixed into the cement grouting materials. However, the toner has a negative effect on the early strength of cement grouting materials. Unfortunately, the mechanism of the negative effects of toner is still unclear, and no effective and targeted measures have been put forward. Hence, the main work of this paper reveals the mechanisms of the toner and nano-SiO₂ (N-S) in the hydration process and the strength generation of the cement grouting materials in the case of different curing ages and nano-SiO₂ contents via the scanning electron microscopy test (SEM), X-ray diffraction test (XRD), differential scanning calorimetry test (DSC), and Fourier transform infrared spectroscopy test (FTRI). Results show that: (a) the toner hinders the generation of AFt and CH crystals (especially for 1-day and 3-day), which delays the hydration process and weakens the early performance of cement grouting materials; (b) the N-S promotes the hydration process and the formation of C-S-H gels, so as to effectively increasing the early strength and reducing (but not eliminate) the adverse effect of toner on cement grouting materials; (c) With the increase of every 1% N-S, the flexural strength of 1-day, 3-day, and 7-day average increased by 11.3%, 2.9%, and 0.9%, respectively, and the compressive strength of 1-day, 3-day, and 7-day average increased by 0.8%, 0.3%, and 0.1%.

Ceramsite concrete is currently one of the most widely used types of lightweight concrete. Although its durability (in terms of permeability, shrinkage, etc.) has been extensively demonstrated, fatigue resistance has not been addressed in previous studies, particularly the impact of ceramsite characteristics on fatigue resistance. Hence, in this study, the fatigue life of ceramsite concrete at different stress levels is investigated using four-point bending fatigue tests. The Weibull distribution test reveal, the effects of ceramsite size and content on the equivalent fatigue life under different failure probabilities. The effects of ceramsite on fatigue resistance are also analysed using SEM. Finally, a uniform fatigue equation considering the ceramsite content, ceramsite size, and stress level is established to predict the fatigue life of ceramsite concrete. The results show that: the equivalent fatigue life of ceramsite concrete increases with 5 – 10 mm and 10 – 20 mm ceramsite contents, especially for 5 – 10 mm ceramsite. Concerning 20 – 30 mm ceramsite, it has a negative impact on the fatigue resistance of ceramsite concrete, particularly at low stress levels. Ceramsite size and content have less influence on fatigue life under stress level variation. The propose fatigue prediction equation concurrently considers the effects of ceramsite content, ceramsite size, and stress level on the fatigue life. The R² values of the prediction equation for different failure probabilities exceed 0.94, thereby proving the reliability of the proposed fatigue equation.

Flocculent basalt fiber (FBF), a natural fiber characterized by high strength, excellent toughness, and environmental friendliness, is an ideal additive for enhancing the road performance of recycled asphalt mixtures. However, existing research on FBF-reinforced recycled asphalt mixtures has largely been limited to single-factor analyses of FBF content, neglecting the synergistic effects of FBF size characteristics (diameter and length) and content. This critical gap restricts the accurate optimization of FBF parameters and the reliable application of FBF in recycled asphalt mixtures. Hence, this study investigates the combined effects of FBF diameter, length, and content on the optimal asphalt–aggregate ratio, mechanical properties, high-temperature rutting resistance, low-temperature cracking resistance, and water stability of SMA-13 recycled asphalt mixtures. A random forest approach is adopted to quantify the relative importance of FBF diameter, length, and content on the optimal asphalt–aggregate ratio and various road performance indexes. The results show that the optimal asphalt–aggregate ratio and road performance indexes increase significantly with increasing FBF content and length but decrease with increasing FBF diameter, with minimal variation in replicate tests. However, when the fiber content surpasses 0.4%, a deterioration in performance occurs. Fiber content has the most significant impact on the optimal asphalt–aggregate ratio and overall road performance, followed by diameter and then length. The optimal fiber content is identified as 0.4% for fibers with a diameter of 6 µm (regardless of fiber length in this study) and 0.3% for fibers with a diameter of 3 µm and a length of 4 mm. These findings provide precise parameter guidance for engineering applications of FBF in SMA-13 recycled asphalt mixtures, thereby promoting the sustainable utilization of recycled materials.

In order to accurately characterize the temperature dependence of the high-temperature performance of asphalt pavement surface layer materials, this paper studies the effects of temperature, load, and number of actions on the high-temperature anti-rutting performance of asphalt pavement surface layer materials (AC-13 and AC-16 mixtures), based on indoor rutting tests, and constructs a high-temperature performance temperature-dependent model and rutting prediction model for surface layer materials. The results show that as the temperature increases, the dynamic stability of the mixture decreases in an S-shaped curve, and the rut depth increases exponentially. The temperature-dependent model transition temperatures for the dynamic stability of 70#, 50#, 30#, SBS, and HMB asphalt mixtures are 39 °C, 44 °C, 46 °C, 56 °C, and 56 °C, respectively. The dynamic stability of modified asphalt mixtures is significantly higher than that of base asphalt mixtures. The depth of wheel ruts is affected by temperature, load, and the number of actions. The variation ranges of the load index k_P, the temperature index k_T, and the number of actions index k_N are 0.727–1.222, 1.926–2.177, and 0.133–0.295, respectively. The correlation coefficients of the wheel rut prediction model are all above 0.95, and the depth of wheel ruts can be predicted by the model.

The examination of crack propagation in concrete under fatigue conditions is crucial for comprehending the mechanisms of concrete fatigue failure. Variations in aggregate types result in notable differences in the fatigue crack propagation characteristics of lightweight concrete compared to ordinary concrete. Consequently, this research focused on analyzing the locations and angles of cracks in ceramsite lightweight concrete subjected to four-point bending fatigue conditions, while accounting for different levels of fatigue loading (i.e., stress levels). Furthermore, the study aimed to clarify the influence of ceramsite size and content on the fatigue crack propagation behavior in ceramsite lightweight concrete. The results indicated that an increase in the replacement rate of 5–10 mm and 10–20 mm ceramsite led to the highest probability of fatigue cracks occurring within the range of 15–45 mm from the specimen center, reaching 41.2% and 44.7%, respectively. The crack angle exhibited an increase corresponding to an increase in the content of 5–10 mm ceramsite, with the maximum average crack angle attaining a value of 86.5°. Conversely, a decrease in the content of 10–20 mm ceramsite resulted in a reduction in the crack angle. However, 20–30 mm ceramsite did not have a significant effect on the characteristics of fatigue cracks. The level of stress predominantly influenced the path of crack propagation. At stress levels of 0.55, 0.65, and 0.75, the highest proportions of crack angles fell within the range of 75° to 80°, with values of 47.1%, 43.8%, and 53.3%, respectively. Furthermore, an increase in stress levels did not affect the location of the cracks.