The reinforcement and durability of loess are of great importance for road performance. In this study, a self-designed grouting system and newly permeable polymers were adopted to investigate the mechanical properties and durability of solidified loess (SL), considering different dry densities and water contents. The unconfined compression test and piezocone penetration (CPTU) test were used to examine the mechanical properties. The mechanism of the loess solidified by permeable polymer was analyzed from the micro-level by SEM, MIP, and XRD tests. The test results show that the effect of polymer grouting is obvious, the unconfined compressive strength (UCS) of the SL after grouting is as high as 3.05–5.42 MPa; it is 11.83–20.99 times that of unsolidified loess (UL). The UCS of the SL after grouting is inversely proportional to the dry densities and water contents. After 56 days of immersion, the SL still shows a high compressive strength. The additional erosion of the SL was not caused by the salt solution; the durability is significantly better than that of cement mixing soil. The sensitivity of various factors on the UCS of the SL are service environment > water content > dry density. The SEM tests clearly show that the gel formed by the reaction of the polymer with water on the surface of soil particles makes the bond of soil particles tighter. It can be observed from the MIP test that the cumulative mercury of SL was 0.115 mL/g, which was 33.72% of UL (0.341 mL/g), and the cumulative mercury of SL after immersion in water and salt solutions was 0.183 mL/g and 0.175 mL/g, which was 53.7% and 51.3% of UL (0.341 mL/g), respectively. The XRD results show that there are no other new mineral components produced after grouting and the spacing between crystalline planes decreases, which proves that permeable polymer grouting makes the soil denser and does not erode the soil particles.

Recently calcium alginate has been successfully applied to encapsulate asphalt rejuvenator, which can protect asphalt rejuvenator from early leakage and release asphalt rejuvenator when triggered by specific factors such as cracks. The interfacial adhesion property of asphalt binder with calcium alginate carrier is of great importance to its actual performance. In this paper, the molecular model of the interface region between asphalt binder and calcium alginate was established, and molecular dynamics simulations were performed on it to investigate the molecular interaction at the interface region. By extracting and processing the data during the simulation process, the interfacial adhesion behavior was expounded using the spreading coefficient (S), permeation depth and permeation degree. Furthermore, the interfacial adhesion strength was evaluated by adopting the interfacial adhesion work. Results showed that the value of S was greater than 0, implying that asphalt binder could wet the surface of calcium alginate. Saturate had the highest value of permeation degree, followed by resin, aromatic and asphaltene. However, asphalt binder could not infiltrate into the interior of TiO₂, only accumulating and spreading on the surface of TiO₂. The interfacial adhesion work of unaged and aged asphalt binder to calcium alginate was −114.18 mJ/m² and −186.37 mJ/m², respectively, similar to that of asphalt–aggregate interface. The van der Waals interactions contributed the most to the formation of the interfacial adhesion strength. In addition, a certain degree aging of asphalt binder and addition of titanium dioxide in the calcium alginate carrier were helpful to enhance the interfacial adhesion strength.

The interface between asphalt and aggregate acts as a key link in load transfer and damage development; its shear mechanical behaviour has a decisive influence on the fatigue cracking and durability of bituminous pavements. In this study, SBS-modified asphalt and limestone aggregate were selected. By precisely controlling the moulding load, asphalt film thicknesses ranging from 23 μm to 219 μm were achieved. Systematic shear tests were conducted within a temperature range of 10 °C to 40 °C to systematically investigate the evolution of interfacial shear strength, stress–displacement curve characteristics, shear fracture energy and failure modes. Two primary failure modes were identified: adhesive failure, defined as debonding at the asphalt–aggregate interface with minimal residual asphalt on the aggregate surface; and cohesive failure, defined as internal rupture within the asphalt film with asphalt residue covering both fracture surfaces. The results indicate that temperature has a significant deteriorating effect on interfacial shear strength; as temperature rises, shear strength decays rapidly at first and then more slowly before gradually approaching zero, whilst shear fracture energy decreases monotonically, with the rate of decay being more pronounced at lower temperatures; the thickness of the bituminous film exerts a monotonically decreasing influence on interfacial shear strength, whilst shear fracture energy remains at a relatively high level within the intermediate film thickness range; bituminous films that are either too thin or too thick are detrimental to the effective dissipation of interfacial energy. An analysis of interfacial failure modes reveals that, under low-temperature conditions, failure occurs primarily at the interface between the asphalt and the aggregate, manifesting as adhesion failure; under high-temperature conditions, the failure path shifts to within the asphalt film, manifesting as cohesion failure. An increase in asphalt film thickness promotes a shift towards cohesion failure, whilst a decrease in film thickness tends to favour adhesion failure; between these two extremes, a coupled and competitive relationship is observed. Based on interfacial thermodynamics and phase transition theory, this study provides an interpretation of how temperature governs the migration of failure modes through alterations in asphalt cohesion, intermolecular forces and interfacial surface tension, and reveals the pivotal role of film thickness in restructuring the distribution of interfacial weak points by regulating the ratio of structural asphalt to free asphalt.