To investigate the effect of styrene-butadiene-styrene (SBS) modifier content on the viscoelastic behavior of SBS-modified asphalt (SBSMA) at different temperatures and phase structures, the star SBS modifier was chosen to fabricate seven types of SBSMA with different contents. Multiple stress creep recovery (MSCR), linear amplitude sweep (LAS), and low-temperature frequency sweep tests were adopted to study the influence of SBS modifier content on the viscoelastic performance of SBSMA at high to low temperatures. The SBSMA’s microstructure with different contents was investigated using a fluorescence microscope. The results indicated that the change in non-recoverable creep compliance and creep recovery rate was bounded by 4.5% content at high temperatures, with an apparent turning point. The changing slope of content at less than 4.5% was much higher than that of the content greater than 4.5%. At medium temperatures, the fatigue life of SBSMA increased exponentially with the rising modifier content. The rate of increase in fatigue life was the largest as the content increased from 4.5% to 6.0%. At low temperatures, the low-temperature viscoelastic property index G (60 s) of SBSMA decreased logarithmically as the modifier content increased. In terms of the microscopic phase structure, the SBS modifier gradually changed from the dispersed to the continuous phase state with the increasing SBS modifier content.

Cement emulsified asphalt mixture (CEAM) is widely used in asphalt pavement for its environmental virtues. However, a CEAM layer can influence fatigue performance of asphalt pavement because of higher air voids of CEAM in contrast to hot mix asphalt (HMA). Therefore, it is common to use HMA and CEAM structure combinations for improving the fatigue performance. In this work, three different thickness structure combinations of HMA (AC-10) and CEAM (AC-16) were designed, in which HMA and CEAM were used as top layer and bottom layer, respectively. The fatigue performance of the three combinations was studied. The fatigue equations of the combinations were established and the rational combination was recommended. The distributions of the internal voids in the combinations were studied with X-ray computed tomography (X-ray CT); and the correlation between the fatigue life and the void ratios were analyzed. Artificial neural network (ANN) was employed to predict the fatigue life of each combination. The results show that the fatigue life of the combinations is inversely proportional to the stress ratio level and environment temperature. The optimal combination is the structure with 40 mm HMA and 40 mm CEAM. The internal void ratio of CEAM is higher than that of HMA. A thinner HMA and thicker CEAM structure can result in higher void ratios and lower fatigue life of the combinations. The prediction results of ANN are similar to the experimental results. The obtained results can potentially guide the design of cement emulsified asphalt pavement structures.

This study presents a deep-learning method for characterizing carbon fiber (CF) distribution and predicting electrical conductivity of CF-reinforced cement-based composites (CFRCs) using scanning electron microscopy (SEM) images. First, SEM images were collected from CFRC specimens with different CF contents. Second, a fully convolutional network (FCN) was utilized to extract carbon fiber components from the SEM images. Then, D_SEM and D_sample were used to evaluate the distribution of CFs. D_SEM and D_sample reflected the real CF distribution in an SEM observation area and a specimen, respectively. Finally, a radial basis neural network was used to predict the electrical conductivity of the CFRC specimens, and its weights (d_i) were used to evaluate the effects of CF distribution on electrical conductivity. The results showed that the FCN could accurately segment CFs in SEM images with different magnifications. D_sample could accurately reflect the morphological distribution of CFs in CFRC. The electrical conductivity prediction errors were less than 6.58%. In addition, d_i could quantitatively evaluate the effect of CF distribution on CFRC conductivity.

Research on phase change materials (PCMs) is booming in the context of global energy structure transitions and the challenge of dealing with temperature fluctuations in engineering materials. Polyurethane solid–solid phase change materials (PUSSPCMs) show great potential for thermal energy storage and temperature regulation because of their designable molecular structure, no risk of leakage, and high bulk stability. In this paper, the recent research progress on PUSSPCMs is systematically reviewed. Starting from the material system, the core preparation process of the PUSSPCMs was elucidated. At the performance improvement level, related performance studies on PUSSPCMs are systematically summarized, focusing on the introduction of dynamic covalent bonds and a nanofiller composite strategy to enhance the thermophysical properties of the materials. At the application level, innovative studies and thermomodulation advantages of PUSSPCMs in different fields are summarized. Finally, for green development, multifunctionalization, and bottlenecks in the scale-up preparation of PUSSPCMs, future research directions for balancing the performance requirements, conducting multi-scale simulations, and exploring green materials are proposed to provide theoretical references for the development and application of high-performance PUSSPCMs.

The current focus of research attention on reclaimed asphalt pavement (RAP) utilization is expanding the applications of RAP. This study aims to analyze the road performance of recycled permeable asphalt mixtures (RPAMs), which represents a novel direction for utilizing RAP. Firstly, the Marshall design method was used to carry out the material composition design of the RPAM with varying RAP contents (10%, 20%, and 30%). Subsequently, the performance of the RPAM with different RAP contents (10%, 20%, and 30%) and preheating temperatures (120 °C, 130 °C, 140 °C, 150 °C, and 160 °C) was tested with a permeable asphalt mixture containing 12% high-viscosity asphalt as the control group. The mixture’s performance included high-temperature stability, low-temperature crack resistance, water stability, anti-raveling performance, and dynamic mechanical properties. The results indicate that the higher the RAP content, the better the high-temperature performance of the RPAM, while the low-temperature performance, water stability, and anti-raveling performance deteriorate. At 30% RAP content, its pavement performance is comparable to that of the control group mixture. However, increasing RAP preheating temperature can improve low-temperature and water stability but may reduce high-temperature performance. The optimal RAP preheating temperature for pavement performance is between 140 and 150 °C. The dynamic modulus test showed that the higher the RAP content, the greater the dynamic modulus of the RPAM, leading to better high-temperature stability but reduced low-temperature crack resistance. The influence of RAP preheating temperature is the opposite. These test results demonstrate the feasibility of utilizing RAP for paving permeable asphalt pavement under controlled RAP content and preheating temperature conditions.

As road base materials, porous cement-stabilised aggregates (PCSA) can reduce the erosion damage caused by the water inside pavement structure. However, due to the reduced deformation resistance and anti-cracking ability associated with the high porosity, the application of PCSA has been held back. A laboratory experiment was conducted in this study to improve the cracking properties of PCSA through the incorporation of the styrene–butadiene rubber (SBR) latex. The effects of the SBR latex usage on permeability, compressive strength, flexural strength and anti-freezing ability (AFA) of PCSA were investigated. In addition, the modification mechanisms of the SBR latex on the PCSA properties were analysed. Test results indicated that the air voids and permeability coefficient decreased with the increase in the SBR latex dosages. The flexural strength and AFA were improved when the SBR latex dosages are between 10% and 15%. 7 d compressive strength has a slight decrease, while the 28 d compressive strength is increased. The significant increase in flexural strength and AFA can be attributed to the interpenetrating matrices formation, stretching effect as well as flexibility enhancement after adding the SBR latex.