The penetration grade system is still widely adopted for selecting asphalt binder with desired paving performance. However, the initial material compositions of asphalt binder with the same penetration level are still different, and vary with the crude oil source and essentially result in different rheological performance. This study aimed to assess the linear viscoelastic (LVE) properties, and high- and intermediate-temperature and microscale characteristics of seven unmodified asphalt binders from different sources and countries with the same penetration level of 70. The LVE parameters were firstly evaluated followed by comparisons to various damage-based indexes. The microstructure of asphalt binders was further investigated followed by correlations between morphology and performance parameters. Experimental results indicate the |G*|/sin δ is well related to the MSCR-based non-recoverable creep compliance; furthermore, the R and |G*|·sin δ can generally represent the LAS-based failure strain and fatigue life, respectively. The viscoelastic nature of tested binders was clearly distinguished and related to rheological performance by atomic force microscopy (AFM). The roughness parameters and the phases’ content derived from AFM images showed significant correlations with LVE characteristics and fatigue resistance nature, respectively. This research provides theoretical foundations for further investigating the rheological performance and microstructure characteristics, and their correlations with asphalt binders.

During its service life, asphalt pavement is affected by environmental factors such as heat, light, oxygen and moisture. The asphalt binder ages, resulting in a decrease in the performance of the asphalt pavement. Therefore, the development and application of an asphalt anti-aging agent is of great significance. In this paper, the road performance of the developed asphalt binder liquid anti-aging agent was verified in the two scales of asphalt binder and asphalt mixture, respectively. Firstly, a simple aging test method was proposed using needle penetration as the evaluation index. The aging time of the simple aging method was determined to be 20 h. Secondly, the addition of anti-aging agents improved the low-temperature performance of the asphalt binder and had a less adverse effect on the high-temperature performance. The test values of needle penetration and the ductility of the asphalt binder increased and the values of the softening point decreased. And the road performance of the anti-aging asphalt mixture basically met the specification requirements. The addition of the anti-aging agent improved the low-temperature performance of the aged asphalt mixture by 16%, which is of great significance for improving the service life of asphalt pavement.

Cement-emulsified asphalt mortar (CA mortar) is an organic–inorganic composite material composed of cement, emulsified asphalt, fine sand, water, and various admixtures. It is mainly used as the cushion layer for high-speed railway ballastless tracks. CA mortar cushion layers in North China often have to withstand the coupling effects of humidity and freeze–thaw, which has a very important impact on the fatigue performance of CA mortar. Based on the big data statistical results, the temperature conditions and cycle times of the CA mortar layer Freeze–Thaw cycle in North China were determined. Also, a fatigue performance test under humidity–freeze–thaw coupling conditions was designed and carried out. The fitting curve equations of fatigue stress and fatigue life under different humidity conditions and freeze–thaw coupling were established. The relationship between fatigue performance parameters K and n and humidity conditions was analyzed. This study shows that with the increase in humidity, the fatigue life of CA mortar under different humidity conditions shows an overall downward trend. The fatigue performance and fatigue life stress level sensitivity of CA mortar decrease with increasing humidity. The proportion of water damage and freeze–thaw damage to total damage increases with increasing humidity, which means that the humidity and freeze–thaw have a more significant impact on the fatigue properties of CA mortar. When the humidity is low, the fatigue cracks of CA mortar are mostly generated across the cement paste, and the macroscopic damage presents as longitudinal cracking. When the humidity is high, the fatigue cracks of CA mortar are mostly generated at the interface between aggregate and paste, and the macroscopic damage presents as oblique cracking. Based on the analysis of the damage mechanism, it is suggested that the humidity of CA mortar should be controlled below 25% in the actual project to ensure its durability.

Laboratory simulation of aging cannot restore the complex aging behavior of bitumen well. The objective of study is to reveal the role of various field aging factors on the aging process of virgin bitumen and SBS(Styrene–Butadiene–Styrene)-modified bitumen. The influence of different field aging factors on aging behavior of virgin bitumen and SBS-modified bitumen were discussed. To achieve this goal, three different field aging styles were used to carry out field aging of virgin bitumen and SBS-modified bitumen. The aging behavior of the two types of bitumen were characterized based on rheological performance, and the influence degree of various aging factors on the rheological performance of bitumen was quantitatively analyzed through the contribution rates. The findings indicated that field aging had an obvious influence on the rheological performance of the two types of bitumen, which showed that the complex modulus, G-R parameter and stiffness modulus increased, and creep rate decreased. The contribution rates significantly indicated the degree of influence of hot oxygen, light and other factors (wind, water, dust, etc.) on the two types of bitumen. Among them, hot oxygen was the main factor leading to the aging of two types of bitumen. The virgin bitumen was not sensitive to aging caused by light, and the aging of SBS-modified bitumen was greatly affected by light. Other field aging factors (wind, water, dust, etc.) led to the aging of virgin bitumen to a certain extent, but inhibited the aging of SBS-modified bitumen.

Foamed asphalt treated mixture is a kind of material whose properties are between semi-rigid and flexible. However, there is not enough information of strength characteristics of this material for us. In this study, we monitored the foamed asphalt treated mixture's characteristics of strength, density and moisture content with different curing conditions to study the formation process and regularity of it's strength character. We investigated the relationship between strength forming and asphalt dispersion with the help of micro-scale analysis observations and it was found that in the study that obtained strength factors for foamed asphalt mixture was directly related to the evaporation of water, (and there was a migration process for asphalt)(no idea what this is for). In this process, asphalt blocked some of the void of test specimen, so that the opening voids decreased and the closed void increased instead. As a result, water stability of foamed asphalt concrete was improved.

The use of Reclaimed Asphalt Pavement (RAP) is a sustainable strategy to conserve natural resources, reduce environmental pollution, and lower construction costs. However, aged asphalt in RAP suffers from oxidation and loss of light fractions, increasing stiffness and brittleness. A key scientific challenge is how to effectively restore the performance of aged asphalt while maintaining cost efficiency. In this study, a novel asphalt rejuvenator was developed to address this issue. The rejuvenator consists of 6% aromatic oil-like materials to replenish light components, 1.52% plasticizer to enhance ductility, and 0.3% modifier A to improve adhesion, with a total dosage of 7.82% by the mass of the aged binder. The rejuvenator meets the requirements of Chinese specifications. The performance evaluation was conducted at both asphalt binder and mixture scales. The results show that the rejuvenator significantly improves low-temperature cracking resistance and medium-temperature fatigue performance of aged binders, although it slightly reduces high-temperature rutting resistance. When applied to asphalt mixtures with 45% RAP, the rejuvenated mixtures exhibited enhanced low-temperature performance. A comparative analysis with commercial rejuvenators confirmed the developed product’s competitive performance and economic benefit. This study provides technical insight into rejuvenator design and addresses critical challenges in RAP recycling for sustainable pavement engineering.