Thermal contraction is a key factor in low-temperature cracking, contributing to internal stresses in the bitumen-aggregate composite. Most macromechanical models treat mastic as a continuous material, limiting an in-depth analysis of the component interactions, which is essential for improved material design. This study analyses the low-temperature behaviour of bitumen and mastic containing different basalt filler content using experimental testing and micromechanical finite element modelling (FEM). The model evaluates micromechanical interactions between bitumen and aggregates, with aggregates modelled as spherical particles in the bitumen. Thermal contraction coefficients are predicted via viscoelastic modelling and compared to experimental results. Findings show higher filler content lowers the thermal contraction coefficient while increasing stress concentrations due to the combined thermal properties of bitumen and filler. The micromechanical model aligns well with experimental data, confirming its reliability in predicting stress distribution and thermal behaviour. These insights enhance the understanding of bituminous materials in cold environments.

Low-temperature cracking is one of the most common failures in asphalt pavements, especially in cold regions. Accordingly, considerable amount of research has been performed in order to understand the low-temperature cracking mechanisms and to propose test methods for characterizing and determining cracking performance of bitumen and asphalt mixtures under freezing conditions. The existing test methods, however, require expensive equipment and skilled technicians; they are thus not well suited for routine tests. As a contribution to mitigate this situation, this study intends to investigate experimentally and characterize numerically the low-temperature cracking behavior of bitumen and mastic materials using a refined thermal cracking test method. The proposed method, the annular restrained cold temperature induced cracking (ARCTIC) test, allows to determine the low-temperature cracking properties of the mastic and bitumen with a relatively simple setup. In this paper, finite element (FE) modeling is used for evaluating the effect of test parameters on the temperature, stress and strain gradients induced in the specimen during the test. The ARCTIC test is employed to measure cracking temperatures of two bitumen and two mastic materials. The measurements repeatability is examined and the effect of bitumen type on the thermal cracking potential of bitumen and mastic is evaluated. FE modeling is employed to examine the effect of thermomechanical parameters on thermal cracking performance of the materials and to back-calculate fracture stress and strain from measurements. The results highlight the potential of the proposed test and analysis method for evaluation of low-temperature cracking in bitumen and asphalt mastic.

Low-temperature cracking significantly affects durability of asphalt pavements. This research addresses the role of the mastic phase by experimentally evaluating the low-temperature cracking performance of selected bitumen and mastics with different filler types and contents. Their thermal contraction coefficient (αT), low temperature viscoelasticity, and strength properties are measured using standard tests like the dynamic shear rheometer (DSR) and fracture toughness tests (FTT). An enhanced laboratory technique, the annular restrained cold temperature induced cracking (ARCTIC) test, is employed to study combined thermal and mechanical effects on low-temperature cracking. The alignment of FTT with ARCTIC results highlights a good correlation between these methods for mastics with nearly the same αT. However, the insensitivity of FTT to αT raises concerns about its applicability to materials with significantly different αT, as it may not capture accurately their performance. The ARCTIC test is free of such a problem and even shows a higher sensitivity to the mastic composition. The findings demonstrate that the addition of filler significantly affects the resistance of mastic to low-temperature cracking by altering its αT. Additionally, the filler content, type, and gradation distinctly impact the thermal and mechanical characteristics of mastics, enhancing their ability to withstand lower temperatures more effectively than bitumen. In particular, adding 50 % by volume of different filler types reduces the αT of mastic by 45–60 % and results in 3–10 °C reduction in cracking temperature (Tcr) measured with the ARCTIC test.

There are various experimental methods for improving the moisture strength of asphalt concrete, such that the most common one being the use of anti-stripping materials. In the present paper, the influences of polymer materials on\ asphalt binder were investigated using repetitive loading test in wet and dry conditions along with thermodynamic parameters based on the surface free energy (SFE) components of asphalt binder and aggregates. The obtained results of this investigation indicate that using styrene butadiene rubber (SBR) polymer has improved the asphalt concrete strength against the moisture damage, especially in the specimens made of granite aggregates. Also, SBR polymer increases the cohesion free energy and reduces the energy released by the system during the stripping event, which represents a decrease in the tendency for stripping. The stripping percentage index, which is obtained by combining the results of the repetitive loading test in wet and dry conditions along with the results of thermodynamic parameters, represents that the specimens made of controlled asphalt binder in the loading cycles under wet conditions have a higher stripping rate. Also, the modulus loss rate in control asphalt concrete is faster than the modified specimens.

In order to increase the life of the asphalt mixture and reduce the cost of the pavement life cycle, methods must be provided to improve the quality. Accordingly, the effects of aggregate surface coating with hydrophobic material in order to modify the aggregate mixture's polar properties and reduce its hydrophilic properties are investigated. To this end, limestone and granite aggregates, 60-70 bitumen, and Two types of additives were used as the primary materials for the construction of asphalt mixtures. Thermodynamic concepts with cyclic loading have been used to evaluate the effects of these additives. The results obtained in this study indicate that the hydrophobic coating on the aggregate surface has increased the acidic components and decreased the alkaline components of the surface free energy for both types of aggregates. These changes will increase the bitumen-aggregate adhesion and make a better coating of bitumen on the aggregate surface. The results based on thermodynamic concepts suggest that the aggregate surface coating has reduced the system's separation energy and the desire for stripping. The results of the dynamic modulus in wet to dry conditions also approve this outcome. The combination of thermodynamic concepts and the cyclic loading results show that the coating on the aggregate surface has reduced the aggregate's stripping from bitumen. It is also obvious that the samples made with granite aggregates, which have acidic properties, are prone to moisture damage and have a higher tendency to strip.