The super absorbent polymer (SAP) has been attracting extensive concerns due to its strong capacity in water absorption and retention. The amorphous hydrogels formed by the post-absorbent SAP have the potential of clogging the micro-cracks in asphalt materials and refraining the rainwater from infiltrating. This provides the possibility of applying SAP in asphalt pavements to seal or fill the cracks and relieve the distresses caused by rainwater infiltration in the underlying layers. Before exploring the cracking sealing mechanism of SAPs in asphalt pavements, a series of experiments were performed to evaluate the feasibility and influences of SAPs in asphalt mastics and asphalt mixtures on their mechanical performances and functionalities. Firstly, the basic properties of SAPs were analyzed, and then the rheological properties of the asphalt mastics using SAP replacing mineral powder (10%, 20%, 30%, and 40% by volume) were explored. The water stability and infiltration reduction effect of the asphalt mixtures incorporated with SAP were evaluated by the Marshall stability test, immersion Marshall stability test, freeze-thaw splitting strength test, Cantabro test, and permeability test. The test results indicated that SAPs could be used in the asphalt mixtures to partially substitute mineral powder with desirable mechanical performances. When less than 10% of the mineral powder was replaced by the SAP, the high-temperature performance and fatigue life of the asphalt mastics could be improved to some extent, but both declined after the content of the SAP was larger than 10%. Due to the hydrogels formed by SAPs after water absorption, the water stability of the asphalt mixtures deteriorated with the increased content of SAPs. Moreover, the results from the permeability tests implied that the SAP hydrogels could fill the seepage channels in the material, thus improving the migration and infiltration resistances of the asphalt mixtures. With the increased contents of SAPs, the permeability coefficients of the asphalt mixtures could be reduced up to 55%. Based on the research findings in this study, when an appropriate amount of SAP was added in the asphalt materials, desirable temperature stability, water stability, and fatigue resistance could be achieved regarding actual requirements from applications. At the same time, the addition of SAPs could effectively refrain the infiltration and migration of rainwater in asphalt pavements, thus potentially mitigating the effect of water erosion on the underlying layers.

Ecological porous concrete (EPC) is one of the novel formulations of concrete with unique phytogenic properties. However, achieving both low alkalinity and high strength in EPC proves challenging due to the inherently high alkalinity of the pore environment, which hinders the growth of the plant and affects its ecological benefits significantly. This research investigated the utilization of 15 types of chemical admixtures and diatomaceous earth as alkali-reducing agents to optimize the properties of silicate cementitious materials for the applications of EPC. To identify the most effective agents, the pH value and compressive strength of the cement paste were adopted as the screening criteria for the selection of the essential alkali-reducing ingredients. Subsequently, a composite approach combining chemical admixtures and DE was employed to explore the synergistic effects on the pH and strength of silicate cementitious materials. The results revealed that a combination of 8% DE, 5% oxalic acid, and 5% iron sulfate functioned effectively and resulted in desirable performance for the concrete. This synergistic blend effectively consumed a large amount of Ca(OH)₂, reducing the pH of cement paste to 10.48 within 3 days. Furthermore, the hydration reaction generated C-S-H with a low Ca/Si ratio, leading to a remarkable increase in the compressive strength of the concrete, reaching 89.7 MPa after 56 days. This composite approach ensured both low alkalinity and high strength in silicate cementitious materials, providing a theoretical basis for the application and promotion of EPC in the ecological field.

Moisture absorbability is the characteristic of autoclaved aerated concrete that differs from other wall materials. For autoclaved aerated concrete, dry-wet circulation is the main actual service environment and can directly affect moisture absorbability, which influences cracking performance of structure. In this study, autoclaved aerated concrete with dry-wet circulation times of 0, 30, 60, 150, and 270 is selected. The experiment is performed under the condition of temperatures 20°C, 30°C, 40°C, and 50°C and relative humidities (RH) of 40%, 60%, and 80%. The temperature and humidity have significant effects on moisture absorption. When the dry-wet circulation times are increased, the moisture absorption performance improves; when comparing the specimen at the dry-wet circulation of 0 times with the specimen of dry-wet circulation of 270 times, the amount of moisture absorption content increased by 85.7%, at the temperature of 50°C and RH of 80%. Origin software is chosen to fit the moisture absorption kinetics model. SPSS software is used to analyse the linear regression and variance. The results of hygroscopic kinetics showed that the fitting effect of the double exponential function was optimal, and the temperature and humidity were closely correlated with the specimens under dry-wet circulation, for R² greater than 0.941.

Crack repairing is considered a cost-effective technique in preventive maintenance, provided that right repairing method and material are selected and properly applied. By means of timely and effective crack repairing manners, the service life of pavement could be increased and leads to significant cost savings for the highway management system. In this study, a chemical grouting method that usually used in the repair of cement concrete structures was employed and modified for the crack repairing of asphalt concrete pavements. In order to evaluate the feasibility and effectiveness of the proposed method, in-situ experiments were performed on several typical pavement sections with all kinds of cracks. Through long-term observation and by comparison with the conventional crack repairing method, the chemical grouting method was proved effective for the crack repairing of asphalt pavements, and exhibited desirable durability under heavy traffic loads.