Mingliang Li

Existing evaluations of highway engineering testing and inspection equipment often overemphasize nominal parameters, directly compare non-equivalent indicators, and lack clear criteria for equipment upgrades. Based on a targeted synthesis of publicly available technical specifications, standards and procedures, and the peer-reviewed literature, this study develops a documentary benchmarking and decision framework for nine categories of testing and inspection technologies across five application scenarios: pavement condition, structural performance, internal quality, construction processes, and material testing. The framework evaluates the available evidence in terms of parameter comparability, explicit performance, system integration, data reliability, and data verifiability. Published manufacturer specifications give maximum testing speeds of 120 km/h for the selected ZOYON-LDD and 80 km/h for Greenwood TSD, but these values do not establish equivalent measurement accuracy or repeatability under matched conditions. In contrast, an FHWA-reported 32-laboratory evaluation of AIMS2 aggregate-morphology testing provided independently assessed angularity coefficients of variation of 2.9% within and 4.3% between laboratories for aggregate sizes excluding 0.075 mm. Public evidence remains insufficient for assessing metrological traceability, raw-data access, and algorithm performance in several other categories. A tiered upgrade pathway prioritizes modular improvements where feasible, complemented by complete equipment replacement when justified. Proposed acceptance criteria emphasize raw-data accessibility, independent verification, and separately reported AI detection and measurement errors, shifting attention from nominal parameters toward reproducible and traceable capabilities.

With the increased application of porous asphalt, the recycling and reutilization of aged materials have become a critical issue for sustainable pavement engineering. This study investigates the evolution of the performance characteristics of porous asphalt mixtures under high-temperature heating conditions, with the aim of providing a theoretical basis for hot in-place recycling (HIR) technology in the rehabilitation of porous asphalt pavements. The heating states of asphalt, mortar and mixtures in HIR were simulated using controlled oven heating. Their microscopic, mechanical and thermal properties were evaluated under different aging conditions and with the incorporation of different rejuvenators. The results show that asphalt aging intensifies with the increasing heating temperature and time. The incorporation of bio-based rejuvenators significantly alleviates aging effects and demonstrates superior performance compared to conventional rejuvenators. Furthermore, aggregates and rejuvenators enhance the thermal conductivity of materials, while aging reduces the thermal conductivity coefficient and increases the risk of temperature gradient diseases. The rheological properties of asphalt are closely related to the degree of aging. While aging mitigation improves low-temperature cracking resistance and acoustic damping performance, it may compromise high-temperature deformation resistance. In conclusion, to achieve an optimal balance between performance recovery and aging control, it is recommended that the HIR of porous asphalt pavements be conducted at a heating temperature of 180 °C for 5 min, with the addition of 3% bio-based rejuvenator.

Coal liquefaction residues (CLRs), including both indirect (ICLR) and direct (DCLR) variants, represent industrial by-products whose conventional landfill disposal raises environmental concerns. This study comparatively analyzes ICLR and DCLR properties against limestone fine aggregates through physicochemical characterization. Results indicate that ICLR contains predominant SiO₂ crystalline phases (50.05%) with trace Fe-Ti-Al-Mg oxides, demonstrating higher Vickers hardness (615 HV vs. 246 HV for limestone) and elastic modulus (98 GPa vs. 81 GPa for limestone), while its apparent relative density (2.612) closely matches that of limestone (2.783). Conversely, DCLR features abundant carbonaceous components (75.9% C) with olefinic/aromatic structures (asphaltene content 66.2%), exhibiting lower mechanical strength (Vickers hardness 21 HV) but enhanced asphalt affinity, as indicated by strong C=C (1591 cm⁻¹) and aromatic C–H (744 cm⁻¹) absorption peaks in FTIR. Both CLRs share comparable gradation curves and micromorphological characteristics with limestone aggregates, including uniform surface scaly textures. While pore-size distributions differ minimally between CLRs, both present finer porosity than limestone and show no leachate toxicity risks, confirming their viability as sustainable alternatives to asphalt fine aggregates.

Extreme rainfall poses an increasing threat to mountainous transportation systems by frequently triggering landslides along road corridors. Most existing studies focus on long-term landslide susceptibility, whereas event-scale assessments remain limited, particularly in road environments. This study develops an event-scale framework for assessing landslide risk along mountain roads under extreme rainfall conditions, using the July 2023 “23·7” rainfall event in Mentougou District, Beijing, as a case study. A Random Forest model was constructed by integrating multi-source geospatial data with an event-specific inventory of 8930 landslides. The model achieved high predictive performance, with ROC–AUC values of 0.9187 and 0.9166 for the validation and test datasets, respectively. Feature importance analysis further indicates that landslide occurrence is controlled by the combined effects of rainfall, terrain conditions, vegetation cover, and anthropogenic disturbance, with rainfall acting as the primary trigger. High-risk road segments are mainly concentrated in the southeastern part of the study area, showing clear spatial clustering. These results highlight the value of event-scale analysis and demonstrate the effectiveness of the road-oriented framework for identifying hazardous segments under extreme rainfall conditions. The proposed approach provides practical support for landslide monitoring, risk mitigation, and resilient management of mountainous transportation infrastructure.

Porous asphalt pavements need to be cured for 24 h~48 h before they can be opened to traffic. In an emergency, physical cooling methods, such as water sprinkling and air blowing, can be used to accelerate cooling, but the effects of the two methods on the mechanical properties and durability of porous asphalt mixtures are still unclear. In this research, firstly, the dropping and rising temperatures of the pavement surface during the water sprinkling process of newly laid porous asphalt mixtures in real projects were analyzed. The effects of the two conditions of water immersion and water sprinkling on the mechanical properties of porous asphalt mixtures were clarified, and water sprinkling technology for porous asphalt mixtures was proposed. Secondly, the effects of air blowing on the temperature reduction and strength loss of porous asphalt mixtures was analyzed, and the pavement surface temperature control standard that was suitable for air blowing was proposed. Finally, a seven-year observation was carried out on the water sprinkling cooling test section in the actual project. The research results show that water immersion or the sprinkling of water repeatedly during the curing period of porous asphalt pavements reduces the strength of the mixture. It is recommended to use a water amount of 0.3 kg/m² once and sprinkling four times before painting road markings and two times after painting road markings; this was the best water sprinkling cooling process for porous asphalt pavements. The use of air blowing can accelerate the temperature reduction of porous asphalt mixtures, but the mechanical properties of the mixtures are attenuated after air blowing. Air blowing can be carried out when the pavement surface temperature is lower than 70 °C. Compared with the road section without water sprinkling for cooling, the use of the determined process to cool the newly laid porous asphalt mixtures by water sprinkling does not have a significant adverse effect on their durability. There is also no significant difference in the performances of the two road surfaces within a seven-year service. In an emergency, physical cooling methods, such as water sprinkling or air blowing, can be used to accelerate the temperature reduction of the newly laid porous asphalt mixtures, so as to achieve the purpose of quickly opening to traffic.

To assess the medium-term performance of porous asphalt pavement during service and its influence on tire/pavement noise level, a seven-year continuous observation and data analysis study was conducted. Key performance indicators were measured and calculated by using automated pavement technology testing equipment. The noise levels were tested by using the on-board sound intensity (OBSI) method on three types of porous asphalt pavements (PUC-10, PAC-13, and PUC-10 + PAC-13) and one dense thin layer course (DTC) for comparison. The findings indicated that the Damage Rate (DR) and Surface Friction Coefficient (SFC) of porous asphalt pavements diminished greatly over time, while the International Roughness Index (IRI) and Rut Depth (RD) remained relatively stable. The two-layer porous asphalt pavement showed the largest noise reduction over the medium-term. Compared to DTC, the OBSI noise levels of these structures were lower by 2.09 dB, 1.53 dB, and 2.88 dB, respectively. The OBSI was found to be closely correlated with the SFC, IRI, test speed, lane, and pavement type. The RD had a notable effect on the OBSI in PUC-10 pavements. In PUC-10 + PAC-13 pavements, a significant linear relationship was observed between the OBSI and SFC. This is mainly because of the polishing of the coarse aggregates, which leads to micro-texture reduction, high frequency noise increase, and SFC decrease. This study makes a valuable contribution to understanding the laws of porous asphalt pavement performance changes and the relationship between tire/pavement noise and pavement characteristics.

As the lifespan of porous asphalt pavement extends, it invariably experiences performance degradation and an increase in tire/pavement noise compared with the original surface when it is newly built. To understand the medium-term performance of porous asphalt pavement during service and reveal the influence of different pavement performance indicators on tire/pavement noise generation, a seven-year continuous observation and data analysis study was conducted. Porous asphalt with different designed material parameters was taken into account, including thin-layer porous asphalt overlay with a maximum nominal aggregate size of 10mm (PUC-10), porous asphalt with a maximum nominal aggregate size of 13mm (PAC-13), and a two-layer porous asphalt incorporating both PUC-10 and PAC-13 (PUC-10+PAC-13). Using automated pavement technology testing equipment, key performance indexes, including damage rate (DR), rut depth (RD), international roughness index (IRI), and sideway force coefficient (SFC), were measured and calculated. The on-board sound intensity (OBSI) method was used to test noise levels in three types of porous asphalt pavement structures and on a dense graded easy compact asphalt concrete (ECA) for comparison. The progressions of the medium-term performances were analyzed according to the measured results. The correlations between tire/pavement noise levels and testing speed, testing lane, pavement structure, and road condition indicators were investigated by regression. The research results revealed that the DR and SFC of the three types of porous asphalt pavement displayed more significant attenuation in the service period, while the IRI and RD showed small changes. Among them, the SFC demonstrated significant attenuation over the first 4 years, decreasing between 13.8% and 17.0%. From the 3-7 years of operation, the transverse crack disease in porous asphalt pavement progressed rapidly. The three porous asphalt pavement structures tested exhibited commendable noise reduction capabilities. Compared to ECA, the OBSI noise levels of these structures were lower by 2.09 dB, 1.53 dB, and 2.88 dB, respectively. Compared to other pavement condition indicators, RD had a more significant impact on the OBSI value of the PUC-10 porous asphalt pavement. For the PUC-10+PAC-13 porous asphalt pavement, there was a significant linear relationship between the OBSI value and SFC, mainly due to polishing of the coarse aggregate surface. It leads to a decrease of the micro-texture, which lies in increasing tire/pavement noise at high-frequency ranges and decreasing SFC. This study will have guiding significance for the research of the attenuated law and durability improvement of porous asphalt tire/pavement noise.

In the maintenance engineering of asphalt pavement, it is often encountered that both the surface and middle layers are damaged and need to be maintained. The cold in-place recycling technology can be used to simultaneously treat multi-layer diseases and reduce the waste of pavement materials. The cold in-place recycling mixture is rarely used for high layer of pavement structure in high-grade highway. In the supporting practical engineering, the emulsified asphalt cold in-place recycling mixtures were paved as the middle layer of pavement structure by the laying of an overlay. In order to comprehensively evaluate the material performances, coring samples were drilled after cold recycling pavement opening to traffic, and different performance tests were carried out based on the coring samples. The newly paved SMA mixtures were set as the control group. The high temperature stability of cold recycling mixture was analyzed by dynamic creep test and MMLS3 accelerated loading test. Then, the cracking resistance of cold recycling mixture was studied by semi-circular bending test. Finally, the effect of curing time on splitting strength of cold recycling mixture was measured, and the moisture susceptibility was analyzed by dry–wet splitting test and freeze–thaw splitting test. The test results showed that the high temperature stability of cold recycling mixture was worse than SMA mixture. For the cold recycling mixture, the deformation value at the early stage and deformation rate at the stable stage were larger than SMA mixture in the accelerated loading process, and shear failure at high temperature occurred earlier. The cracking resistance of cold recycling mixture was worse than SMA mixture because of the aging effect of the old asphalt and adverse influence of the added cement binder. The effect of curing time on splitting strength of cold recycling mixture was significant, and two stable periods of early strength were, respectively, reached after curing 3 days and 7 days. The indexes of moisture susceptibility, including dry–wet splitting strength ratio and freeze–thaw splitting strength ratio, were obviously lower than that of SMA mixture, and the test values not up to the standard requirement existed. For the emulsified asphalt cold in-place recycling mixture, the improvement of material performances should be focused on, especially the moisture susceptibility. In the research, the emulsified asphalt cold in-place recycling mixtures were acceptably used as the middle layer of maintenance pavement structure. The reliable discussions were summarized based on coring samples collected from real-life road sections. The case can provide guidance and reference for similar engineering applications.

This Special Issue “Sustainable Designed Pavement Materials” has been proposed and organized as a means to present recent developments in the field of environmentally-friendly designed pavement materials. For this reason, articles included in this special issue relate to different aspects of pavement materials, from industry solid waste recycling to pavement materials recycling, from pavement materials modification to asphalt performance characterization, from pavement defect detection to pavement maintenance, and from asphalt pavement to cement concrete pavement, as highlighted in this editorial.

High-viscosity modified asphalt is mainly used as a binder for porous asphalt in China and Japan. In order to meet the demand for using porous asphalt under high temperature condition in Africa, high-viscosity asphalt made from low-grade matrix asphalt, which is commonly used in Africa is investigated. Based on simulation of local climate in Africa, the suitable range of high viscosity additive content for different matrix asphalt was obtained by analyzing dynamic viscosity of the asphalt. Through PG high temperature grading, multi-stress repeated creep, accelerated fatigue, temperature sweep and other tests, changes of high temperature, anti-fatigue and anti-shear indicators before and after modification were compared and analyzed and effects of different matrix asphalt were also studied. Finally, considering engineering requirements, mixing and compaction temperatures of various high-viscosity modified asphalt were determined through study of viscosity-temperature characteristics. This research provides a support for preparation of high-viscosity modified asphalt and porous asphalt mixture by using low grade asphalt. The research achievements can help to guide the material design and application of porous asphalt in Africa and other high temperature areas.