To meet the needs of the road industry for maintenance operations, a new cement emulsified bitumen mixture (CEBM) with early-strength, self-compacting, and room-temperature construction characteristics was designed. The strength formation mechanism of CEBM was revealed with a scanning electron microscope (SEM) and the surface free energy (SFE) theory. The mechanical properties and road performance of the CEBM were investigated extensively. The results show that before the demulsification of emulsified bitumen, the SFE of the bitumen–aggregate–water three-phase system was reduced due to the replacement of the bitumen–aggregate interface with water. The adhesion work between the emulsified bitumen and the aggregate is negative, which means the adhesion between the emulsified bitumen and the aggregate will not occur spontaneously due to the existence of water. The liquid emulsified bitumen improves the workability of the mixture and ensures that the mixture can be evenly mixed and self-compacted. After demulsification, the work of adhesion between the residual bitumen and the aggregate is positive, which means residual bitumen and aggregate can bond spontaneously. In addition, the hydration products of cement and aggregate form a skeleton, and the emulsified bitumen film wraps and bonds the cement and aggregate together, creating strength. The emulsified bitumen, cement content, and curing conditions have significant effects on the stability of CEBM. The recommended dosage of emulsified bitumen and cement is 8% and 8–10%, respectively. This material integrates the hardening effect of cement and the viscoelastic performance of bitumen and has good workability, mechanical properties, and road performance. Therefore, the CEBM is technically feasible for application to bitumen pavement.

During the service period, asphalt materials are affected by various natural factors, including heat, ultraviolet light, oxygen and moisture, etc., resulting in the reduction of pavement performance, the increase of pavement distress and shortening of service life. This study aims to investigate the aging performance of asphalt under multiple aging conditions of heat, UV and aqueous solution. Thermal-oxygen aging, UV aging and hydrostatic erosion tests were carried out sequentially on asphalt. The rheological properties, chemical structure and element composition of asphalt were characterized before and after aging, and the effect mechanism of multiple conditions was discussed. The results show that the multiple conditions of heat and UV can increase the rutting resistance and weaken the cracking resistance of asphalt. However, the effect degree of UV decreases gradually with the deepening of aging degree. Additionally, the effect of water on the physicochemical properties is less than that of UV; however, water can increase the sensitivity of physicochemical properties to UV. In summary, this study explored the short-term cycling effect of heat, light and water on asphalt and provided an idea for simulation test of asphalt under multiple aging condition.

In this paper, a method to predict the healing effect of induction heating asphalt concrete at vertical depths was proposed and verified. At first, AH-70 asphalt concrete and SBS modified asphalt concrete of AC-13 gradation were designed and prepared. R-DT (Relationship of Depth and Temperature) was quantified through induction heating test. R-HT (Relationship of Healing rate and Temperature) was quantified through fracture-healing–fracture test and X-ray micro computed tomography test with oven heating. Then, linear regression was used to verify the rationality of R-HT compared with the pre-relationship in previous studies. Finally, R-DH (Relationship of Depth and Healing rate) was predicted by fitting approach. It was found that R-DT and R-HT presented significant linearity, the existence of which was independent from the type of asphalt materials. While, more sensitive of SBS modified asphalt concrete showed that the response to gradient characteristics of R-DT was related to the higher overall temperature. Additionally, R Square-values = 0.963 of linear regression proved the oven heating method was suitable for the quantification and prediction of gradient characteristics. Furthermore, the prediction of R-DH was obtained successfully, which established the continuous distribution of the healing effect at vertical depths and revealed the linear relationship of the continuous distribution.

Remarkable variances were observed in permanent deformation curves of a dense asphalt mixture captured in triaxial repeated load permanent deformation (TRLPD) tests. In order to explore the causes of such variances, each permanent deformation curve was characterized firstly by an indicator (B) of the permanent deformation rate at a steady state stage. Meanwhile, a linear relationship was found between the values of indicator B and the resilient moduli of specimens after 1000 load repetitions. Secondly, a profound discussion on the potential relationship between resilient moduli and air voids content was performed. The discussion showed that air voids content appears to have no contributions to the observed variances. Nevertheless, three failure modes, tension failure, shear failure and shear failure with barreling, were observed in the X-ray Computed Tomography (CT) images of failed specimens subjected to triaxial compressive stresses. Furthermore, a significant correlation between failure modes and the resilient moduli was found by means of one-way analysis of variance (ANOVA). Moreover, it was found that the internal weak zones observed in the CT images of intact specimens dominate the behavior of the permanent deformation of asphalt mixture and the internal structure is the essential cause of such variances in the case of this study. This exploration highlights the influence of the internal structure on the mechanical performance of asphalt materials and thus recommends that considerable attention should be paid on the internal structure other than the volumetric properties when selecting test specimens.

In this paper, steel slag/steel fiber composite asphalt mixture were prepared. The effects of the addition of steel slag and/or steel fibers on the mechanical, thermal, induction heating and healing properties of asphalt mixture were investigated. The results showed that adding steel slag and/or steel fibers improves the water stability, particle loss resistance and fracture energy of asphalt mixtures. The addition of steel fibers increased the thermal conductivity and thermal diffusion of the asphalt mixture, and steel slag showed a reverse effect. Steel slag asphalt mixture cooled more slowly than steel fiber asphalt mixture, which is beneficial to crack healing of asphalt mixture. The composite of steel fibers and steel slag can enhance the induction heating speed, heating homogeneity and thus enhance the induction healing ratio of asphalt mixture. It is concluded that steel slag/steel fibers composite asphalt mixture achieves good mechanical and induction healing properties.

In this paper, the induction healing behaviors of both warm mix asphalt and hot mix asphalt were investigated and compared through damage-healing-damage test. The steel fibers used for making asphalt mixture conductive were first optimized according to the thermal conductivity and induction heating speed of the mixture. Then, the gradient induction heating characteristics, cracking and fatigue resistance, and self-healing ratios of both warm mix asphalt and hot mix asphalt were studied. It is found that warm mix asphalt and hot mix asphalt have similar induction heating speed. The Aspha-Min based warm mix asphalt shows slightly higher fatigue resistance but slightly lower self-healing ratios than hot mix asphalt mixture. Both warm and hot mix asphalt mixtures have very high fatigue life ratios with induction heating, which means that induction heating can improve the durability of WMA. The optimal induction heating temperature of warm mix asphalt is slight lower than that of hot mix asphalt due to the remaining active ingredient, which also deceases the healing ratio slightly. It is also found that the healing ratios of both warm and hot mix asphalt mixtures are highly strain-dependent and the mixtures obtained best healing behaviors at medium microstrain amplitudes.

In this paper, the flow behaviors of asphalt binders were investigated through DSR viscosity-frequency sweep test to find out their potential optimal self-healing temperatures and the real self-healing ratios of the binders at different temperatures were measured through fatigue-healing-fatigue test to confirm the optimal self-healing temperatures. The healing time of asphalt binders needed for full healing was studied as well. It is found that both fresh and aged Pen bitumen binders show near-Newtonian fluid state at their softening point temperatures, at which asphalt binders showed optimal self-healing properties to heal fatigue damage. It is also found that ageing of the binder increases its optimal self-healing temperature. It means that the optimal temperatures of asphalt binders are associated to the bitumen type and ageing. Finally, the Wool and O's Connor model can be used to determine the healing time needed by asphalt binder to achieve full healing, where the accumulated dissipated energy recovery is recommend as a suitable healing index.

Porous asphalt concrete is widely used as a surfacing layer on highways in the Netherlands because of its benefit that it is effective in reducing traffic noise. However, the service life of porous asphalt wearing courses is limited due to the fact that it is vulnerable to raveling. A preventive maintenance strategy using surface treatment material is being considered as a cost-effective and environmentally sustainable option to extend the service life of existing porous asphalt wearing courses. In this paper, the effect of a surface treatment to porous asphalt wearing courses is discussed. A surface treatment material was sprayed on the porous asphalt pavement surfaces in two field trials. Computed Tomography (CT) scans were performed on the porous asphalt concrete cores from the field trials to measure their volumetric properties. The rotating surface abrasion tests were used to determine the raveling resistance of the porous asphalt concrete samples. Finite element models with a realistic structure of the porous asphalt concrete were created for analyzing the stresses and strains as a result of traffic loads in the pavement surface with the surface treatment material. It is found that the effect of the surface treatment is positive.

Ceramic fiber, with a major composition of Al₂O₃ and SiO₂, has advantages of stability at relatively high temperature, big specific surface area and resistance to external mechanical vibration. It has the potential contribution of improving the rutting resistance and temperature sensitivity of modified asphalt binder by proper modification design. In this research, ceramic fiber was introduced into both pen 60/80 and pen 80/100 asphalt binder by different weight ratios. An asphalt penetration test, softening point test, ductility test and dynamic viscoelastic behavior were conducted to characterize and predict the ceramic fiber modified asphalt mortar (CFAM). Research results indicated that the ceramic fiber has a great effect on reinforcement of asphalt, which makes the asphalt stiffer so that the asphalt can only undertake less strain under the same stress. The heat insulation effect of the ceramic fiber will improve the temperature stability. Complex modulus and phase angle results indicate that the ceramic fiber can significantly enhance the high temperature resistance of soft binder.

A preventive maintenance strategy of spraying rejuvenators on asphalt pavement surfaces is being considered as a cost-effective and environmentally sustainable option to extend the service life of existing asphalt concrete pavements. Rejuvenators might penetrate into the asphalt concrete and soften (rejuvenate) the bituminous binder. In this paper, the rejuvenation effectiveness of two rejuvenators on an artificially aged mortar is assessed. Cylindrical mortar specimens were prepared from the artificially aged mortar and then treated by the rejuvenators. The rheological and shear fatigue properties of the reference and treated mortar specimens were measured using dynamic shear tests. Meantime, a three-dimensional column model was created to investigate the dynamic shear test's capability of detecting the rheological properties of a composite column with a soft material in its outer part and a stiff material in its inner part. From finite-element modeling, it is found that the shear modulus of the composite column is higher than that of the soft material and lower than that of the stiff material. However, the results of the dynamic shear tests show that the two rejuvenators did not decrease the complex shear modulus of the artificially aged mortar. In addition, the two rejuvenators did not change the shear fatigue life of the artificially aged mortar.