Polyester-fiber-reinforced cement-stabilized concrete is widely adopted to prevent the shrinkage cracking in pavement engineering. However, the effects of fiber length and content on the dry shrinkage and temperature shrinkage are not clear. The relationship between shrinkage resistance and strength is also discussed scantily. Hence, five types of polyester fiber length (1 cm, 3 cm, 5 cm, 7 cm, and 9 cm) and six types of polyester fiber content (0.1‰, 0.3‰, 0.5‰, 0.7‰, 0.9‰, and 1.1‰) were selected to prepare the fiber-reinforced cement-stabilized concrete. The dry shrinkage coefficients and temperature shrinkage coefficients were used to evaluate the shrinkage resistance. Moreover, the relationships among these shrinkage coefficients, compressive strength, and splitting strength at different curing ages were investigated to realize the prediction of shrinkage resistance of polyester-fiber-reinforced cement-stabilized concrete. This study aimed to seek the optimal fiber characteristics and conveniently evaluate the shrinkage resistance for the polyester-fiber-reinforced cement-stabilized concrete. Results show that: increasing the content of polyester fiber can significantly improve the shrinkage resistance of cement-stabilized concrete, especially for the temperature shrinkage. The fiber length should not be too long, especially for dry shrinkage. The optimum fiber content and fiber length is 0.7‰ and 5 cm for the dry shrinkage resistance and 0.7‰ and 9 cm for the temperature shrinkage resistance. There was higher correlation between compressive strengths and shrinkage coefficients, while the correlation between splitting strength and shrinkage coefficients was not obvious.

Aggregate–asphalt adhesion plays an important role in the water stability of asphalt concrete. In various test standards of different countries, it is evaluated via the subjective judgment of testers using the boiling water test. The subjective judgment in the test method is detrimental to the accuracy of the adhesion evaluation. However, there is no quantitative evaluation method for the aggregate–asphalt adhesion in existing studies. Moreover, the effects of aggregate shape on adhesion are also not discussed and stipulated. Hence, an innovative method based on the Chinese boiling water test and image processing technique is put forward to quantificationally evaluate the aggregate–asphalt adhesion. Moreover, the effects of aggregate shapes on adhesion are also investigated via the proposed method from a view of aspect ratio and homogeneity. Results show that the peeling of the asphalt membrane on the aggregate surface is more serious as the complexity of the aggregate shape increases after the boiling water tests, while the effect degree gradually decreases. The effect of aspect ratio on the peeling status of asphalt membrane is lower than that of aggregate homogeneity.

High-modulus asphalt mixtures (HMAM) have been widely used in asphalt pavement in high-temperature areas of China, owing to their advantages in rutting and fatigue resistance. However, moisture and temperature interdependently determine the degradation of pavement performance of the HMAM, owing to the unique climatic conditions in summer in some high-temperature areas of China. There were few studies on the rutting and fatigue properties of the HMAM under the combined action of moisture contents and temperatures. Hence, the moisture absorption characteristics of the HMAM at different temperatures were analyzed. The rutting performance of the HMAM was investigated under different moisture contents and temperatures. The fatigue performance of the HMAM was investigated under different moisture contents, temperatures, and stress levels. Results show that: the rutting and fatigue resistance of the HMAM decrease with the increase in temperature and moisture content. The dynamic stability decreases by 8.9% at 40 °C and by 7.0% at 60 °C on average per 10% increase in moisture content and decreases by 22.7% on average per 10 °C increase in temperature. The fatigue life decreases by 4.1% at 15 °C and by 3.1% at 40 °C on average per 10% increase in moisture content and decreases by 31.3% on average per 10 °C increase in temperature. Finally, a prediction equation was established to predict the fatigue life under different moisture contents and temperatures.

Particle media are widely used in engineering and greatly influence the performance of engineering materials. Asphalt mixtures are multi-phase composite materials, of which coarse aggregates account for more than 60%. These coarse aggregates form a stable structure to transfer and disperse traffic loads. Therefore, knowing how to adjust the structural composition of coarse aggregates to optimize their performance is the key to optimize the performance of asphalt mixtures. In this study, the effects of different roughness and different sizes on the interlocking force and contact force of coarse aggregates were investigated through means of simulation (DEM), and then the formation-evolution mechanism of the coarse aggregate structure and the role of different sizes of aggregates in the coarse aggregate structure were analyzed. Subsequently, the optimal ratio of coarse aggregates was explored through indoor tests, and finally, the gradation of asphalt mixture based on the optimization of fine structure was formed and verified through indoor tests. The results showed that the major model can effectively reveal the role of different types of aggregates in the fine structure and the relationship between the strength of contact forces between them and clarify that the strength of the fine structure increases with the increase in aggregate roughness. Hence, the coarse aggregate structure can be regarded as a contact force transmission system composed of some strong and sub-strong contact forces. Their formation-evolution mechanism can be regarded as a process of the formation of strong and sub-strong contact forces and the transformation from sub-strong contact force to strong contact force. Moreover, the dynamic stability of the optimized graded asphalt mixture was increased by 30%, and the fracture toughness was increased by 26%.

Ceramsite concrete is one of the most widely used lightweight concretes at present. Although mechanical properties of ceramsite concrete have been extensively discussed, its permeability characteristics are neglected in previous studies. Considering the importance of permeability resistance to concrete, the permeability grade and residual compressive strength after permeability of ceramsite concrete are analyzed in this study. The influence of ceramsite content and size on the permeability grade and residual strength of ceramsite concrete were investigated by the orthogonal experimental method. To further understand the above influence, an improved Bayesian framework for small sample data is also established to analyze the permeability grade and residual strength. Results show that the water–binder ratio and the content of 20–30 mm ceramsite aggregates are the most and least significant influencing factors affecting the permeability characteristics, respectively. The 5–10 mm and 10–20 mm ceramsite aggregates play secondary roles. Increasing 5–10 mm and 10–20 mm ceramsite aggregates is not helpful for improving the permeability resistance of ceramsite concrete. Compared with the orthogonal method, the proposed Bayesian framework is a useful tool for revealing the effects of various factors, which can cut the time cost and provide parameter visualization for the analysis process. Results show that the permeability resistance and residual strength of ceramsite concrete are improved significantly under optimal conditions. The permeability grade and residual strength are increased 200% and 80.3%, respectively. In addition, the residual strength may be more suitable for evaluating the permeability characteristics than the permeability grade.

The disposal of phosphogypsum has emerged as a significant challenge for the phosphorus chemical industry in China in recent years. Utilizing phosphogypsum in alkali-activated materials represents an effective approach to valorize this byproduct. The alkali modulus is a critical parameter affecting the performance characteristics of phosphogypsum-based alkali-activated materials. This study aims to investigate the effects of the alkali modulus on the early-age properties (setting time, fluidity, flexural strength, and compressive strength) and hydration mechanisms of slag–phosphogypsum composite alkali-activated materials (HSFP) across various slag–phosphogypsum–fly ash systems, thereby identifying the optimal alkali modulus. The findings demonstrate that an alkali modulus of 1.35 optimally enhances the mechanical performance of HSFP. At this specific modulus, the equilibrium between alkalinity and soluble silica availability facilitates complete hydration, resulting in a dense gel-crystal microstructure characterized by the highest C-(A)-S-H gel content (58.2%) after 28 days. The effect of the alkali modulus on mechanical properties is contingent upon the fly ash-to-phosphogypsum (FA:PG) ratio, whereas its effect on fluidity and setting time is negligible. The effect of alkali modulus on the strength of HSFP is significantly affected by the fly ash-to-phosphogypsum (FA:PG) ratio. At an FA:PG ratio of 4:6, the flexural strength initially decreases and then increases as the alkali modulus values increase, while the compressive strength shows a consistent upward trend. At FA:PG ratios of 1:5 and 1:9, the flexural strength increases linearly with the alkali modulus, whereas the compressive strength first rises and then experiences a slight decline. These results offer both theoretical insights and practical guidance for the optimization of phosphogypsum-based cementitious material formulations, thereby supporting their potential for large-scale application.