Mansour Fakhri

Low‑temperature cracking is one of the main causes of asphalt pavement damage in cold regions. While many parameters influencing its low-temperature performance are well-studied, the specific effect of the cooling rate during freeze-thaw cycles (FTCs) on the fracture performance of asphalt mixtures remains largely unexplored. In this study, the effect of cooling rate on the fracture toughness (FT), fracture energy (FE), and cracking‑resistance index (CRI) of asphalt concrete is investigated. For this purpose, dry and saturated semi-circular bend (SCB) samples were subjected to seven FTCs at different cooling rates (0.1, 0.2, 0.5 °C/min, and the shock‑freeze state) and temperatures (− 5 °C, − 15 °C, and − 20 °C), after which they were fractured under a fixed mixed‑mode I/II loading conditions. The results of this study show that increasing the cooling rate reduces all three parameters: FE, FT, and CRI. For instance, applying FTCs with a cooling rate of 0.1 °C/min was significantly less damaging, resulting in a 16% and 20% reduction in FT and FE, respectively, compared to 23% and 48% for the shock‑freeze state. Furthermore, increasing the cooling rate reduces both the displacement and the peak load at the time of fracture. This degradation is attributed to insufficient time for viscoelastic stress relaxation at rapid cooling rates, which promotes a brittle response characterized by higher stiffness and a greater tendency toward elastic behavior. Other factors also contribute to the reduction in mechanical performance, such as the increased thermal gradient between the core and surface, rapid freezing of surface water compared to core water, and volumetric expansion of trapped water within the core. These phenomena collectively increase thermal stresses and accelerate the formation of microcracks. Finally, the influence of temperature in FTCs was characterized: decreasing the temperature reduced the displacement at failure, whereas the peak load first increased down to − 15 °C before decreasing at lower temperatures.

This study presents a framework for detecting polished asphalt pavement surfaces by integrating texture-based image analysis with interpretable Machine learning (ML). Polishing, caused by aggregate degradation and bitumen aging, alters surface texture and reduces skid resistance, posing a safety risk. A real-world dataset of 12,480 pavement images was analyzed using 24 texture features derived from the Gray Level Co-occurrence Matrix (GLCM), capturing directional spatial patterns of surface roughness. Several ML models were trained and optimized with the Hyperopt framework, with a Backpropagation Neural Network (BPNN) achieving the highest classification accuracy of 96.1%. Feature contributions were interpreted using SHapley Additive exPlanations (SHAP), providing physical insight into texture-driven polishing mechanisms. Although a ResNet50-based CNN achieved slightly higher accuracy (98.7%), its high computational cost limits practical deployment. The proposed GLCM-ML approach offers an interpretable, efficient, and physics-aware tool for pavement condition monitoring, with potential to enhance predictive modeling of surface texture evolution.

Due to environmental pollution and the shortage of nonrenewable natural resources in road construction, the use of copper slag as a new material in asphalt pavement has been recently evaluated for its ability to reduce the accumulation of waste and lower the cost of asphalt mixture production. The main purpose of this study was to assess the feasibility of using copper-slag filler as a substitute for lime in warm-mix asphalt (WMA) to enhance its self-healing and thermal/electrical conductivity potential. To this end, an X-ray fluorescence (XRF) test was first conducted to analyze the copper-slag filler constituent elements that affect its microwave heating. Then, the self-healing potential of asphalt samples containing copper-slag filler under microwave heating was investigated using thermal imaging, and an index was presented to analyze the fracture energy and load-bearing capacity at each stage of the fracture-healing test. Moreover, an image processing technique was used to determine its capability for uniform heat transfer. Finally, some tests were performed to study the asphalt mixture heat-transfer potential and determine its thermal/electrical conductivity. The results show that the mixtures containing copper slag had high thermal/electrical conductivity. Thermal conductivity, microwave heating uniformity, and self-healing potential (asphalt resistance against reloading) of asphalt mixtures increased with an increase in the copper-slag filler content. With 40, 50, and 60 s of microwave heating, the samples containing copper slag had an average of 14%, 31%, and 37% better recovery, respectively, than the asphalt samples containing 100% of lime filler.

Utilizing the self-healing properties of asphalt materials is a way to improve the service life of asphalt pavements. Enhanced self-healing capabilities can be achieved through mixture modification. Using waste or by-product materials to modify asphalt mixtures can provide further environmental benefits. However, with a given mixture modification method, the resulting materials should be adequately vetted to ensure that enhanced self-healing capability is not attained at the expense of the mixture’s overall performance. This research aims to investigate the feasibility of using zinc slag filler to enhance the self-healing properties of warm mix asphalt (WMA) and evaluates the rutting susceptibility and moisture-resistance of the slag-modified mixtures. To this end, zinc slag filler was used to replace a portion of the mineral filler at different replacement rates in WMA mixtures. Self-healing capabilities of the resulting mixtures were studied under microwave induction heating. The influence of zinc slag modification on asphalt mixture’s characteristics and conventional performance indicators were evaluated by the Texas boiling test, the three-point bending test, and the Kim test (a deformation test). Also, the adhesion between bitumen and aggregate was evaluated using the broken sample from the three-point bending test and digital image analysis. The results of self-healing tests demonstrated that the heat generation capability of the specimens increased with filler replacement rate, such that the specimens with 100% of the mineral filler replaced with slag showed the highest heating performance. Zinc slag filler showed the potential to improve the moisture resistance of WMA by enhancing aggregate–bitumen adhesion and thus reducing stripping. The slag-modified WMA samples exhibited better tensile strength ratio (TSR) and deformation resistance than their non-modified equivalents.

Pavement roughness, commonly estimated by the International Roughness Index (IRI), plays an essential role in pavement assessment. However, accessibility to IRI data requires the operation of profiling equipment, which may be costly for the agencies. In this regard, the use of IRI prediction models from pavement distresses could be an alternative solution. In this research, 507 kilometres of asphalt pavements in Kermanshah, Iran, were investigated using IRI and Pavement Surface and Evaluation Rating (PASER) as a rapid and cost-effective index. The IRI prediction models from PASER were developed using regression (R² = 0.66) and Artificial Neural Network (ANN) (R² = 0.69). Regarding the restrictions of the results, the data clustering using k-means and fuzzy c-means (FCM) was taken into consideration to acquire the IRI ranges based on the pavement condition. Using the FCM as the superior approach, the IRI prediction model from PASER and the corresponding membership degrees was developed based on ANN. The results of model development (R² = 0.97) and validation (R² = 0.85) indicated the desirable performance of the ANN model. This case study can be counted as a practical approach for the agencies to economically investigate the pavement condition, predict the roughness, and also make decisions for maintenance targets at the network level.

This study evaluates the influence of polymer-modification on the induction heating capability of asphalt mastic in a microwave field, and investigates how effectively this approach can be utilized for ice melting and self-healing purposes. To this end, different asphalt mastic mixtures with different polymer-modification and mixing procedures were tested under microwave field exposure for induction heating capability, ice-melting ability, and self-healing capacity. The mixtures were made through warm-mix and hot-mix procedures with four bituminous binders, including virgin (unmodified) asphalt and the same binder modified with three types of polymers. The results showed the effectiveness of microwave induction heating of asphalt mastic for both crack-healing and deicing purposes. The binder type was found to influence the ice melting and crack healing rates, such that using a warm-mix asphalt binder resulted in a more efficient heat generation and conduction than using a virgin asphalt binder. While polymer-modification undermined induction-heating, ice-melting, and self-healing performances, SBS-modified asphalt binders exhibited better performance than the other polymer-modified binders.

The effects of recycled crumb rubber up to 25% replacement of fine and coarse aggregates in two discreet gradations combined with 0% to 25% substitution of cement by silica fume were studied on the mechanical and fracture properties of self‐compacting concrete (SCC). For acquiring a diverse means of comparison, toughness index and energy absorbency of different mixtures were tested, and stress intensity factors of different mixtures were obtained. Additionally, statistical analyses were conducted to verify the validity of the results, and also, regression analyses were conducted to predict the values of flexural strength, toughness index, energy absorption, and fracture toughness of SCC mixtures. The results show that the addition of crumb rubber reduces the modulus of rupture, energy absorbency, and fracture toughness values, but the incorporation of silica fume can compensate for the losses. Conversely, there was a large rise in toughness index when adding crumb rubber.