Alkali-activated materials (AAMs), as eco-friendly alternatives to Portland cement (PC), have attracted increasing attention of researchers and users in the past decades. Despite the eco-friendly nature of AAMs, doubts about these materials as an essential ingredient of concrete exist, regarding, for example, their volume stability. One possible volume change concerns autogenous shrinkage. Autogenous shrinkage is the self-created volume reduction of materials due to chemical reactions without the need for substance or heat exchange with the environment. If the autogenous shrinkage of a binder material is too large, cracking might happen, which will seriously impair the durability of concrete. The aim of this chapter is to provide a state-of-the-art review on the autogenous shrinkage of AAMs. The different characteristics and mechanisms of autogenous shrinkage of different AAMs are reported. Corresponding shrinkage-mitigating strategies are summarized. Existing models to simulate and predict the autogenous shrinkage of AAMs are reviewed. Remarks are then given on testing methods of autogenous shrinkage, which link back to the determination of the magnitude of autogenous shrinkage of AAMs. Connections between autogenous shrinkage and other deformations such as drying shrinkage, thermal deformation and creep are also discussed. Research gaps and outlook on future research in this field are given in the end.

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.

This paper presents an experimental investigation on the potential utilization of one natural zeolite as an internal curing agent for mitigation of self-desiccation and the subsequent autogenous shrinkage of cement paste with low w/b ratio (0.25). Incorporation of 20% zeolite by mass leads to higher internal relative humidity (90.4%) during the first 7 d compared to that of control sample (78.1%). It is indicating that the zeolite under investigated shows partially elimination effect on the self-desiccation and the autogenous shrinkage as well based on the time-zero defined by the onset of internal relative humidity drop. To obtain improved internal curing property, attempts have been done to modify the pore structure of zeolite by acid treatment and/or thermal treatment. However, both nitric acid treatment and thermal treatment shows negative effect on the improvement of internal curing property of zeolite. Because nitric acid treatment tends to increase the BET surface area of zeolite by increasing the volume of 2–7 nm pores, and the thermal treatment tends to reduce the porosity rather than to enlarge the pore size of zeolite.

A 2D lattice model was constructed to simulate crack process of in shell-interlayer-cement paste zone. The simulated tensile strength was validated by an experimental uniaxial tensile test and used as the input for a 3D lattice model, which was constructed to perform mechanical analysis based on a series of 2D X-ray microtomography images. The fracture behaviour of the 3D lattice model with assigned mechanical properties gave a similar crack pattern and tensile strength as the real structure. This study is expected to provide a feasible approach for investigating the fracture and trigger behaviour miccrocapsules embedded in a self-healing cementitious system.