The deterioration of asphalt surface texture under traffic loading leads to a significant reduction in skid resistance and greatly impacts driving safety. However, the influence of dynamic surface texture wear on actual tyre–pavement contact remains unclear. To investigate the impact of asphalt surface texture wear on the evolution of tyre–pavement contact characteristics and their effects on skid resistance, accelerated loading wear tests were conducted and the pavement surface textures after wear were evaluated through high-resolution three-dimensional texture scanning and finite element simulation. The results indicate that asphalt pavement skid resistance decayed non-linearly with texture wear, following a logarithmic trend. Dense-graded mixtures exhibited a temporary recovery, whereas gap-graded mixtures decayed steadily. The contact area of Open Graded Friction Course (OGFC) mixtures exhibited an ‘S’-shaped evolution with wear, while mixtures with pronounced macrotexture showed lower actual contact. The Asphalt Concrete (AC) mixture exhibited the lowest adhesion coefficient and the highest load sensitivity. The multivariate regression models accurately predicted skid resistance, with interfacial adhesion remaining the primary determinant. This study provided a theoretical basis and a technical approach for the accurate prediction and long-term design of asphalt pavement skid resistance.

ABSTRACT Cold mix asphalt concrete (CMA) is widely used for road repair and leveling because of its simple production process and low cost. This study evaluated bottom ash (BA), a coal combustion by-product, as a partial replacement for fine aggregate in CMA. BA-incorporated CMA (BA-CMA) was assessed in terms of Marshall properties, indirect tensile strength (ITS), indirect tensile resilient modulus (ITMR), indirect tensile fatigue life (ITFL), rut depth, and skid resistance. A laser confocal microscope with image analysis was also used to examine asphalt film thickness. The results showed that BA increased asphalt film thickness because of its porous structure, rough surface texture, and low specific gravity, which enhanced asphalt emulsion absorption. Under indirect tensile loading, performance improved with increasing BA content up to 25%, at which ITS and ITMR increased by 24.2% and 26.8%, respectively, while ITFL improved at all stress levels. Fatigue modeling showed a log-log linear relationship between ITFL and tensile strain, indicating that BA mainly influenced fatigue performance through modulus modification. Under compressive loading, rut depth decreased with increasing BA content, reaching a 37.6% reduction at 50% BA. All mixtures satisfied the minimum skid resistance requirement. Although 25% BA increased cost by 17.2%, it provided the most favorable performance-to-cost balance for low- to moderate-load pavements.

The tie-bar gap in jointed cement concrete pavement (JCP) widening severely affects pavement performance. Improving the design strength of tie-bars is the most cost-effective solution. To explore a strategy for improving the design of tie-bars in JCP widening, we constructed a refined numerical model of a widened JCP using the KENSLABS program. The interactions between non-uniform support, additional settlement, and the tie-bar gap were elucidated, and the influence of the tie-bar gap on the pavement deflection and load transfer efficiency (LTE) was revealed. On this basis, the weights of the diameter, spacing, support modulus and elastic modulus of the tie-bar on the LTE were further analyzed, and specific improvement standards for the tie-bar design strength were proposed. The study lays a theoretical foundation for the design standard of tie-bars in the JCP widening project and provides a direct design reference for practical engineering projects.

Full depth reclamation (FDR) with cementitious binders is progressively being implemented in India for rehabilitating the distressed low-volume roads (LVRs). Unlike conventional cement-treated base (CTB) mixes, FDR mixes are highly heterogeneous, comprising reclaimed bituminous materials, aggregates from granular layers, subgrade soil, and varying binders. Extensive laboratory testing evaluated the fatigue performance of CTB and FDR mixes stabilised with Ordinary Portland Cement (OPC) and Portland Pozzolana Cement (PPC). The FDR mixes exhibited lower flexural strength (<1 MPa) and modulus (1700–2700 MPa) than the CTB mixes, along with greater variability in fatugue behaviour. Initial tensile strains ranged from 115 to 568 µε. A laboratory fatigue constant of 600.9 was established; after applying a lab-to-field shift factor of 1.55. This exceeded the upper limiting value of the in-service fatigue constant having flexural modulus less than 5000 MPa. Therefore, a conservative in-service fatigue constant of 439 was calculated, based on AUSTROADS (2017). Incorporating reliability considerations for LVR design, this study proposes a fatigue equation and pavement design catalogues for varying traffic levels, subgrade conditions, and crack relief options. Future refinement of shift factors is recommended as more field data become available.

Pavement response monitoring (PRM) supports infrastructure management by evaluating pavement performance and optimizing maintenance strategies. This study experimentally validates a continuous PRM system using embedded geophones and accelerometers to measure pavement surface deflections under real traffic loads. The system is designed as a cost-effective and easy-to-install solution for continuous pavement deflection monitoring. Field experiments were conducted on the E16 Motorway in Borlänge, Sweden, a cold-climate region, where sensor signals were collected from passing heavy vehicles. Geophones and accelerometers measured pavement vertical vibration velocity and acceleration, respectively. Signal processing methods, including filtering, integration, and transformation, were applied to derive vertical pavement surface deflections. Measured deflections were compared with theoretical values calculated using the multilayer elastic response software ERAPave, showing low normalized root mean square error (NRMSE). Both sensor types accurately captured pavement surface deflections; however, geophones performed better, with an average NRMSE of 9.87% compared to 11.92% for accelerometers. Geophone measurements also showed close alignment between measured and calculated peak deflections, achieving an R² of 80%. This validation confirms the potential of embedded geophone and accelerometer setups as scalable, low-cost solutions for continuous PRM to support roadway maintenance and infrastructure durability.

ABSTRACT Fundamental shear strength parameters, cohesion and frictional angle, offer significant insights into the shear characteristics of cold recycled materials and are good indices for mechanistic-empirical design models of cold recycled pavements. Material preparation, testing procedures and analysis are, however, often labor-intensive, costly, and time-consuming, necessitating efficient and practical alternatives for parameter estimation. This study employs a modeling framework to predict the shear strength characteristics of engineered emulsion-stabilized cold recycled materials. Data from monotonic triaxial shear tests were modeled using two machine learning approaches, namely, (1) self-validating ensemble modelling, which integrates multiple linear regression (forward selection, adaptive least absolute shrinkage and selection operator, elastic net) & neural network configurations, and (2) support vector regression. Based on model performance evaluations through a range of statistical error metrics, support vector regression demonstrated high accuracy and generalizability, identifying mixture coarseness and density as primary factors influencing cohesion, while stabilizer content and chemical additive presence were important for frictional angle. The predicted parameters were further validated within the deviator stress ratio framework, showing strong alignment with experimentally computed results. As an outcome of this study, a user-friendly Microsoft Excel-based predictive tool was developed to facilitate efficient shear parameter prediction and support pavement design and evaluation.

ABSTRACT The Balanced Mix Design (BMD) has emerged as a promising approach for mitigating cracking in high reclaimed asphalt pavement (HRAP) mixtures. This study evaluated the cracking performance of a control asphalt mixture and five BMD-optimized asphalt surface mixtures. The mixtures featured various RAP contents, two binder performance grades, a recycling agent, and a warm mix asphalt additive. The analysis integrated continuous longitudinal strain monitoring from Accelerated Pavement Testing (APT), cracking surveys, and laboratory tests. To quantify APT-measured cracking performance, three primary response phases were identified from the continuous strain monitoring. Residual strain was used to determine the initiation of cracking, and deformation uniformity was employed as a data quality indicator. The findings from strain analysis matched APT cracking surveys. Laboratory tests on field cores confirmed no structural damage for the evaluated mixtures, except for a 60% RAP section. All other BMD mixtures demonstrated better cracking resistance over the control mixture, with HRAP BMD mixtures (>30% RAP) outperforming conventional RAP mixtures (≤30% RAP). Correlation analysis between APT and BMD tests examined and supported the corresponding laboratory test thresholds. This study enhanced insights into pavement performance monitoring and highlighted the efficacy of the BMD concept in optimizing the design of HRAP mixtures.

ABSTRACT Pavement texture polishing under vehicle loads is the main cause of skid resistance degradation. For Portland cement concrete (PCC) pavement, the repeated vehicle load is directly borne by the surface mortar. However, no standardized polishing method exists to characterize the skid resistance degradation of the surface mortar, and the mechanism of the texture evolution and skid resistance degradation during polishing remains unclear. In this study, the 3D topography scanning and the British pendulum tester were utilized to investigate the texture evolution of the surface mortar and its impact on skid resistance during accelerated polishing. A multi-scale analysis method based on the bearing area curve (BAC) and power spectral density (PSD) analysis was proposed. The relationship between the surface mortar texture and British pendulum number (BPN) under dry and wet conditions was established. The results indicate that the high-frequency texture of the surface mortar exhibits a non-uniform vertical distribution. The top topography corresponding at 10% material ratio (mr) shows the strongest correlation with BPN under dry conditions. For wet conditions, the texture with wavelengths λ > 0.25 mm provided by fine aggregates is key to enhancing the skid resistance. The findings provide a theoretical basis and technical guide for PCC pavement texture optimization.

ABSTRACT Sulfidic copper tailings (SCTs) pose environmental risks and are underutilised in construction because of acid generation and sulphate release. This study employs calcium carbide slag (CCS) as a sustainable alkaline activator, alongside fly ash and M32.5 cement, to develop SCTs-based road base materials (SRBM). We systematically investigated the oxidation of SCTs compounds and the performance of SRBM mixtures with varying CCS content and sulphur levels (4%–10%). The results indicate that CCS enhances pyrite oxidation, promoting the formation of ettringite and gypsum, which densifies the microstructure and improves the strength, achieving a 28-day unconfined compressive strength (UCS) of up to 4.08 MPa. All mixtures successfully immobilised heavy metals, with leaching concentrations below regulatory limits. Crucially, a pilot-scale road section constructed with the optimal mix (TP6) demonstrated excellent engineering performance, including a soaked CBR exceeding 70% and a resilient modulus over 500 MPa, complying with local standards. A comparative analysis revealed that the CCS-activated SRBM reduces embodied carbon by approximately 46% and material cost by 35% compared to conventional lime-stabilised bases. This work validates CCS-activated SRBM as a mechanically robust, environmentally safe, and economically viable alternative for sustainable road construction.

The present study focuses on developing a framework for performance-based mixture design for cold recycled emulsified mixes (CREMs) using simple performance tests, namely the indirect tensile asphalt cracking test (IDEAL-CT) and the ideal rutting test (IDEAL-RT). However, currently, no acceptance limits exist for these tests to screen the performance of CREMs. Therefore, critical threshold values were proposed and recommended using Receiver Operating Characteristic (ROC) statistical analysis. To achieve the goal, forty-two mixes with different combinations were prepared in the laboratory using a gradation with a 19 mm nominal maximum aggregate size (NMAS), seven different sources and varying dosages of Cationic Slow Setting emulsion (CSS-2), with and without cement. The samples were compacted to a target air void of 11% ± 1% using a Superpave gyratory compactor (SGC), indirect tensile strength (ITS), cracking (IDEAL-CT) and rutting (IDEAL-RT) tests were performed. Using ROC analysis, preliminary acceptance threshold limits for these performance tests were recommended, as 40 for CTIndex at 25 °C and 55 for RTIndex at 40 °C. The study found that the performance-based design approach could more effectively distinguish between cracking or rutting susceptible mixes compared to the conventional ITS-based design. Additionally, a performance space diagram (PSD) was developed based on the established thresholds to categorise the mixture types. The study also emphasised the importance of selecting an appropriate binder content during the mixture design process for the production of better performing cold recycled mixes.