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Delaminated MXene was incorporated into cement to improve the properties of cement composites, and its effects on the hydration process, microstructures, and mechanical properties were investigated, respectively. The investigation results showed that delaminated MXene was well-dispersed in the cement matrix and significantly reinforced the compressive strength of cement, especially when the addition is 0.01 wt%. Meanwhile, the total hydration heat of cement hydration and the quantity of hydration products were increased with the addition of delaminated MXene. In addition, the formation of HD C-S-H gel was promoted, and the microstructure of hydrated cement became more compact.

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Microbially induced calcium carbonate precipitation (MICP) technology has attracted widespread research attention owing to its application in crack healing for cement-based materials in an intelligent and environmentally friendly manner. However, the high internal alkalinity, low nutrient content, and dense structure of cement-based materials have restricted its application in self-healing cement-based materials. Various carrier materials have been widely used for the immobilization of microorganisms in recent years. Carrier materials have significantly increased the ability of microorganisms to withstand extreme conditions (high temperature, high alkali, etc.) and have provided new ideas for the compatibility of microorganisms with cement-based materials. In this study, the basic principles of microbial self-healing technology in cement-based materials and microbial immobilization methods and the influencing factors are introduced, followed by a review of the research progress and application effects of different types of carrier materials, such as aggregate, low-alkali cementitious materials, organic materials, and microcapsules. Finally, the current problems and promising development directions of microbial carrier materials are summarized to provide useful references for the future development of microbial carriers and self-healing cement-based materials.

Shrinkage reducing agent (SRA) is one of chemical admixtures for concrete during mixing, which was developed to reduce drying shrinkage in concrete due to low surface tension. The frost resistance of mortar incorporating the traditional type SRA could be reduced. Therefore, the modified type SRA was developed to improve the frost resistance. In this study, shrinkage properties, frost resistance, pore structure and characteristics of pore solution in the mortar using the traditional and modified types SRA were discussed. It was suggested that the characteristics of pore solution in addition to the pore structure affected the shrinkage properties and frost resistance.