This study investigates the application of foam asphalt (FA) to enhance the compaction effectiveness of a hot in-place recycling asphalt mixture (HIR-AM) during the HIR process of old road surfaces. Initially, the process parameters for FA preparation were determined through expansion-rate and half-life tests. Subsequently, the study focused on evaluating the impact of FA on the compaction quality of HIR-AM. Performance assessments were conducted through rutting tests, low-temperature bending tests, Hamburg wheel tracking tests, dynamic modulus analyses, and various other experiments to evaluate the road performance of HIR-FAM. Finally, the research findings were validated through practical engineering applications, and the construction process for HIR-FAM was summarized. The research results reveal that the optimal foaming temperature for SBS asphalt is 170 °C, with an ideal water content of 1.7%. Under the same compaction temperature, HIR-FAM demonstrated a significant reduction in void content, ranging from 3.8% to 21.2% compared to HIR-AM. Moreover, a higher proportion of FA usage resulted in a more substantial decrease in void content. Compared to HIR-AM, HIR-FAM exhibited notable improvements, including an 11.6% increase in dynamic stability, a 13.4% enhancement in bending strength, a 13.3% increase in maximum bending strain, an 8.1% improvement in residual stability, and an 8.5% boost in freeze–thaw splitting strength. Furthermore, HIR-FAM demonstrated superior water-thermal stability and resistance to low-frequency loads. Paving a test road verified that the adoption of foam asphalt in thermal recycling led to a compaction density increase of over 0.79% compared to traditional in situ thermal recycling sections, with improved compaction uniformity.

Self-melting ice asphalt pavement materials inhibit pavement freezing and improve driving safety. This paper aims to study the long-term salt release characteristics of self-melting ice asphalt mixtures and the impact on pavement after complete salt release. Firstly, a method to accelerate the rapid release of salt based on the Los Angeles abrasion tester. Then, long-term salt release patterns were elucidated under the influence of deicing agent dosage, type of asphalt, and type of gradation. Finally, a quantitative analysis of the pavement performance after complete salt release is conducted. The results indicate that the release efficiency of the Los Angeles abrasion tester method has increased by 91 times compared to the magnetic stirrer immersion flushing method and by 114 times compared to the natural soaking method. The SBS-modified self-melting ice asphalt mixture possesses a longer duration of salt release, but the uniformity of salt release is inferior. Salt release duration is directly proportional to the dosage of deicing agents. SMA-13 self-melting ice asphalt mixture exhibits poorer uniformity in salt release. After complete salt release, high-temperature stability of self-melting ice asphalt mixtures decreased by 31.6%, low-temperature performance decreased by 15.4%, water stability decreased by 26.7%, and fatigue life decreased by 35.9%.

To evaluate the effect of Microbial Induced Calcium Carbonate Precipitation (MICP) on the enhancement of early resistance to sulfate attack of cementitious materials. In this paper, firstly, the effect of Bacillus subtilis (BM) on the carbonation depth as well as the carbonation rate of standard as well as carbonation-conditioned cementitious sand specimens was investigated. Secondly, the compressive strength and volumetric deformation of the specimens at different ages of immersion in sulfate solution were investigated. Finally, the changes of hydration products before and after the addition of BM were analyzed by X-ray diffraction analysis (XRD), and the microscopic pore structure of the specimens after erosion was analyzed by low-field nuclear magnetic resonance (LF-NMR) and scanning electron microscope (SEM), which revealed the mechanism of the improvement of BM on the resistance to sulfate erosion of the cementitious materials. The results showed that the initial compressive strength of BM carbonised curing specimens, ordinary carbonised curing specimens and BM standard curing specimens were increased by 42.0%, 34.0% and 4.0%, respectively, compared with the ordinary standard curing specimens, respectively, compared with the control group, and the loss of the final compressive strength was reduced by 37.4%, 25.4%, and 14.5%, and the expansion rate was reduced by 31.3%, 22.0%, after sulfate erosion for 6 months, 5.2%, and porosity decreased by 24.2%, 13.6%, and 9.9%. Microbial mineralization accelerated the reaction between Ca²⁺ in the pore solution and atmospheric CO₂, and the calcite formed filled the pores to make the structure denser, increasing the initial compressive strength of the specimens and reducing the loss of properties when exposed to sulfate solution. Therefore, the application of MICP technology in cementitious materials provides a new direction for the development of durable and sustainable cementitious materials.

In order to improve the reclaimed asphalt pavement (RAP) dosing and the road performance of recycled asphalt mixtures, this study prepared epoxy recycled binder (ERB) and epoxy recycled mixtures (ERMs) by dosing epoxy asphalt, respectively. The rheological characteristics and microstructure of ERB were comprehensively analyzed using a dynamic shear rheometer (DSR), a bending beam rheometer (BBR), and fluorescence microscopy (FM). The road performance of ERM was evaluated by a four-point bending test, a rutting test, trabecular beam bending test, a freeze–thaw splitting test, an immersion Marshall test, and a uniaxial compression dynamic modulus test. Grey relational analysis (GRA) was used to quantify the correlation between the dosage of epoxy system and road performance indicators. The results show that, after the addition of the epoxy system, the high- and low-temperature rheological properties of ERB were improved by 458.3% and 97.9% compared with those of ordinary asphalt, and the high-temperature performance and fatigue performance of ERM were improved by 220.4% and 80.5% compared with SBS-modified asphalt mixtures. The dynamic modulus test showed that the dynamic modulus of ERM was positively correlated with the dosage of epoxy system. GRA showed that the dosage of epoxy system was most closely related to the fatigue performance of recycled mixtures.

Severe asphalt ageing and the difficulty in dispersing agglomerated particles within reclaimed asphalt pavement (RAP) hinder the uniform blending of virgin and aged mineral aggregates during plant-mixed hot recycling, compromising the durability of the recycled asphalt mixture. To accurately quantify the degree of blending between virgin and aged aggregate during thermal recycling and to optimise the mix design and mixing process for thermally recycled asphalt mixtures, a test method has been proposed. This method comprises key steps, including the preparation of asphalt mixtures, separation of virgin and aged materials, separation of the binder from aggregate, and calculation of the blending degree. It analyses the impact of varying mixing conditions on the blending degree of virgin and aged aggregate during the thermal recycling process. The results indicate that complete homogenization of virgin and aged aggregates during mixing is unattainable, with blending efficiency ranging from 40% to 60%. Increasing the amount of RAP has a negligible effect on blending efficiency. Appropriate increases in the amount of rejuvenating agent, mixing temperature, mixing time, and asphalt content enhance blending efficiency by 10% to 30%. The mixing sequence where RAP is first blended with virgin aggregate before incorporating virgin asphalt further enhances the blending efficiency of virgin and aged aggregates by approximately 20%. However, mixing temperatures exceeding 160 °C and mixing times exceeding 270 s caused secondary ageing of the asphalt, adversely affecting the blending degree of virgin and aged aggregates.