As an organic solvent, naphthenic oil is used widely in the polymer industry, so it has the potential to be used with polymer to improve the performance of asphalt binder in pavement engineering. The effects of naphthenic oil as an additive for styrene-butadiene-styrene (SBS)–modified asphalt were investigated in this paper. Penetration, softening point, ductility, rheology property before and after aging, morphology observation, and storage stability were tested on naphthenic oil/SBS-modified asphalt. The following findings were achieved: Naphthenic oil increases the consistency and temperature sensitivity of SBS-modified asphalt. It is remarkably beneficial to the low-temperature property of SBS-modified asphalt. It is not advantageous to the resistance to deformation. Naphthenic oil is beneficial to the antiaging property of SBS-modified asphalt and helps the polymer to get swollen, proving that naphthenic oil has some properties of aromatics. Another discovery is that naphthenic oil makes the SBS distribute more evenly, which is consistent with the discovery in the rubber industry. Future investigation of its use with other additives and the anti-ultraviolet light (UV) aging properties are suggested.

In this paper, the effects of NaCl concentration on saturation in concrete and ice-formation pressure and volume expansion of solutions are investigated; also, mechanisms of concrete salt-frost scaling are analyzed. Results show that the ice-formation pressure and volume expansion of solutions are significantly reduced with increased NaCl concentration, which positively affects the reduction of salt-frost scaling of concrete. On the other hand, the capillary-uptake degree of saturation and water-uptake rate in concrete obviously increase with increased NaCl concentration, which negatively affects the reduction of salt-frost scaling. According to the measured data, the ice-formation pressure in concrete is calculated, and the result quantitatively proves that the ice-formation pressure generated by 2–6% NaCl solution causes maximal concrete damage.

This study investigates the skid resistance performance of asphalt mixtures containing composite aggregates of basalt and limestone. The research aimed to predict the service life of the asphalt mixtures and identify the optimal basalt content for enhanced performance. Using an accelerated friction tester, friction indices such as the British pendulum number (BPN), mean texture depth (MTD), and dynamic friction coefficient (Dµ) were measured. The study conducted accelerated wear tests on mixtures with varying basalt contents under different water flow rates and loads. Results indicate that anti-skid performance decreased with increasing water flow, load, and wear cycles, initially showing a sharp decline followed by a gradual stabilization. Orthogonal experiments determined that basalt content had the most significant impact on skid resistance, followed by load and water flow rate. By converting skid resistance and MTD values into IFI values, a four-area diagram was created to illustrate skid resistance deterioration. The four-area IFI diagram also demonstrated that higher basalt content significantly enhances the skid resistance and service life of asphalt mixtures. Cost analysis based on life prediction showed that a 40% basalt content mixture is cost effective while maintaining excellent skid resistance. A test section study further validated that a 40% basalt content ensures good skid resistance, with indoor test predictions aligning closely with field data. Although the test section has been operational for only two years, ongoing monitoring will provide further insights into long-term skid resistance performance.

The air void system purposely introduced by an air-entraining admixture (AEA) is of great significance for the protection of concrete from freeze–thaw damage. Fly ash has been globally used in concrete, while the unburnt carbon in fly ash can adsorb AEA molecules and, thus, increase the AEA demand. Previous studies primarily focused on the air content of fresh fly ash concrete. This paper aimed to explore the stability and distribution of air voids in fly ash concrete at the fresh state. To achieve this goal, eleven different fresh fly ash concrete mixtures with an initial air content of 6 ± 1% were prepared in the laboratory. Samples were taken at various times within 75 min after initial mixing to investigate the air content and air void distribution in fly ash concrete at the fresh state using a super air meter (SAM). The results indicated that there was no significant correlation between loss on ignition (LOI) of fly ash and AEA demand to achieve the initial air content of 6 ± 1%. Class C fly ash concrete tended to have a better air content retention than Class F fly ash concrete. Compared with LOI, AEA demand had a stronger correlation with air content retention. Most of the fly ash concrete mixtures had a satisfactory air void system immediately after mixing, but the SAM number showed an increasing trend over time, suggesting the coarsening of the air void system with time.

Loading tests were carried out on the dowel bar-concrete substructure of concrete pavement. Mechanical characteristics of dowel bar-concrete interaction were studied. In the elastic range of concrete, the bearing modulus, which is a crucial parameter but is usually determined by presumption, was calculated using classic Westergaard equations. Its influencing factors were evaluated such as concrete strength, dowel bar thickness, joint width, and anti-cohesive layer. Besides, a theoretical equation for tangential stress at the most dangerous point of concrete was deduced from Westergaard's and Timoshenko's equations. The equation reveals how the tangential stress of the most dangerous point at the dowel bar-concrete interface is affected by influencing factors. Lastly, the deterioration process of concrete around the dowel bar was revealed. The strain gauges’ data show that deterioration of concrete develops from the most dangerous point to far away from the dowel bar gradually. Two failure modes were found; one is circular spalling, the other is three main cracks. The initiation of the dowel-bar concrete structure's deterioration is circular spalling, attributed to high radial compressive stress in concrete. The deterioration starts around half the load capacity of the structure.