The generation and development of interfacial adhesion properties between the asphalt binder and the aggregate surface is difficult to explain at the microscale through experiments. In this research, the models of asphalt–aggregate interface were constructed using four-component molecules of asphalt overlaid on two typical minerals of aggregate, respectively. Then the diffusion law of asphalt on the surface of aggregates and interfacial behaviour at microscale were analysed through the calculations of the diffusion coefficient, the Z-axis direction relative concentration and the dipole moment. Moreover, the distribution characteristics of four components of asphalt in the Z-axis direction in the asphalt–aggregate interface were analysed. The results showed that the increase in temperature could benefit the diffusion of asphalt on the aggregate surface and promote the adhesion between asphalt and aggregate. From the energetics perspective, the Van der Waals force between molecules was found to be the main factor driving the molecular movement during the diffusion process of asphalt on the surface of aggregate. Based on the molecular orientation theory, it was concluded that the polarity of asphalt and aggregate is the fundamental cause of adsorption of asphalt on the aggregate surface, and asphaltene and gelatine play an important role in adhesion of asphalt to aggregate.

Low temperature negatively affects the engineering performance of cementitious materials and hinders the construction productivity. Previous studies have already demonstrated that TiO₂ nanoparticles can accelerate cement hydration and enhance the strength development of cementitious materials at room temperature. However, the performance of cementitious materials containing TiO₂ nanoparticles at low temperatures is still unknown. In this study, specimens were prepared through the replacement of cement with 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, and 5 wt.% TiO₂ nanoparticles and cured under temperatures of 0°C, 5°C, 10°C, and 20°C for specific ages. Physical and mechanical properties of the specimens were evaluated through the setting time test, compressive strength test, flexural strength test, hydration degree test, mercury intrusion porosimetry (MIP), X‐ray diffraction (XRD) analysis, thermal gravimetric analysis (TGA), and scanning electron microscopy (SEM) in order to examine the performance of cementitious materials with and without TiO₂ nanoparticles at various curing temperatures. It was found that low temperature delayed the process of cement hydration while TiO₂ nanoparticles had a positive effect on accelerating the cement hydration and reducing the setting time in terms of the results of the setting time test, hydration degree test, and strength test, and the specimen with the addition of 2 wt.% TiO₂ nanoparticles showed the superior performance. Refined pore structure in the MIP tests, more mass loss of CH in TGA, intense peak appearance associated with the hydration products in XRD analysis, and denser microstructure in SEM demonstrated that the specimen with 2 wt.% TiO₂ nanoparticles exhibited preferable physical and mechanical properties compared with that without TiO₂ nanoparticles under various curing temperatures.

Smartphones have integrated various sensors (e.g. GPS, acceleration sensor) and can be used to evaluate roads roughness. In this study the theoretical algorithm, in which the vehicle suspension parameters were included, would be established to calculate International Roughness Index (IRI) from acceleration using smartphones. Firstly, based on Android Studio 2.0, a client application installed on smartphones was developed. Next, the physical parameters of a quarter actual vehicle model (QAVM) were identified utilizing the front wheel drop test in accordance with complex modal theory. Then, the relationships among acceleration, IRI and the profile elevation were established through the derivation of theoretical formula. Finally, a validation analysis was implemented to evaluate the feasibility and reliability of this methodology. The validation experimental results on three asphalt pavement segments indicated that the collected acceleration data utilizing smartphone were basically consistent with that by accelerometers. Meanwhile, IRI calculated by the proposed theoretical methodology was close to that obtained by digital survey vehicle (DSV) and the maximum relative error between them was below 10%. Overall, due to the consideration of vehicle dynamic characteristics, the proposed method could improve the measurement accuracy and enable various vehicles to be used for road roughness evaluation.

To study the rheological and aging properties of vegetable oil–based polyurethane (V-PU) modified asphalt, V-PU terminated with an –NCO group was synthesized from renewable castor oil, and liquefied MDI-100LL and 10–40 wt% V-PU modified asphalts were prepared. Temperature classification, multiple stress creep recovery (MSCR), and linear amplitude scanning (LAS) tests were carried out. The results showed that the modulus, the creep recovery rate (R), and the yield stress and yield strain of the V-PU modified asphalts significantly increased in the order: 0 wt% < 10 wt% < 20 wt% < 40 wt% < 30 wt%, while the phase angle and the unrecoverable creep compliance (Jnr) changed in the opposite order, and the high temperature grade of 30 wt% V-PU modified asphalt was 4 grades higher than that of the base asphalt, which indicated that the addition of V-PU enhanced the fatigue, permanent deformation, and recovery deformation resistance. The 30 wt% sample exhibited phase inversion had the best performance. Comprehensive FTIR, GPC, and fluorescence microscopy analyses showed that the molecular weight significantly increased and the V-PU molecules agglomerated after aging. The excess –NCO groups of V-PU prepolymer react with water in the air and the active hydrogen in the asphalt system and finally form a cross-linked three-dimensional network structure with the asphalt to improve performance. The mechanism of intramolecular cementation reaction and the aging process of V-PU modified asphalt was creatively derived.

In some regions with hot summer and cold winter, most modified asphalt mixtures cannot meet the requirement of high-temperature stability and low-temperature cracking resistance simultaneously very well, so rutting or cracking often occurs in these regions. This paper tries to use nano-CaCO₃/SBR (Styrene butadiene rubber) and nano-ZnO/TiO₂/SBS (Styrene–butadiene–styrene) composite modified asphalt mixtures to solve this problem. The properties of these two asphalt mixtures were compared with those of base, SBR modified and SBS modified asphalt mixtures through rutting, beam bending, immersion Marshall, freeze–thaw splitting, three-point bending fatigue and splitting tests. Results show that the high-temperature stability of nano-CaCO₃/SBR composite modified asphalt mixture is better than that of SBR modified asphalt mixture, and their low-temperature cracking resistances are close. In addition, the water stability, fatigue performance, performance after ageing, and splitting strength of SBR modified asphalt mixture can be improved by the addition of nano-CaCO₃. All of the performances mentioned above of nano-ZnO/TiO₂/SBS composite modified asphalt mixture are better than those of base or SBS modified asphalt mixture. In summary, nano-CaCO₃/SBR or nano-ZnO/TiO₂/SBS composite modified asphalt mixture has good high-temperature stability and low-temperature cracking resistance and can be used in the regions with hot summer and cold winter.

Although epoxy resin-modified asphalt mixture (ERMAM) shows excellent performances as used in bridge deck pavement, its cost is high and low-temperature anti-cracking resistance is poor, so unsaturated polyester resin-modified asphalt mixture (UPRMAM) is proposed to replace ERMAM. However, there is still a great gap in strength between UPRMAM and ERMAM. In this paper, 4,4′-bismaleimidodi-phenylmethane (BDM)/unsaturated polyester resin-modified asphalt mixture (BDM/UPRMAM) is presented for bridge deck pavement. Marshall, splitting, three-point bending, rutting, bending creep, immersed Marshall, freeze–thaw splitting, four-point bending fatigue and oil corrosion tests are performed to compare the performances of BDM/UPRMAM, pure unsaturated polyester resin-modified asphalt mixture (PUPRMAM) and ERMAM. Results show that the addition of BDM into PUPRMAM makes the splitting tensile strength, flexural-tensile strength and dynamic stability increase by 17.6%, 29.2% and 80.94%, respectively. It also improves the resistance to water damage and fatigue disease significantly while it decreases low-temperature performance. Compared with ERMAM, BDM/UPRMAM has similar splitting tensile strength, worse flexural-tensile strength, dynamic stability and fatigue resistance, better low-temperature crack resistance and lower cost. As a result, BDM/UPRMAM can be used as the bridge deck surfacing material.