Durability failure is a challenge facing the sustainable development of society. How to improve the durability of structural concrete with low cost and high efficiency is a key problem to be solved. This review represents the research progress on durability enhancing admixtures in concrete crack control, microstructure regulation and reinforcement rust resistance improvement, and points out the existing problems of various admixtures.

1) Concrete crack control is a premise of structural concrete durability improvement. However, how to further improve the effectiveness and adaptability of admixtures according to the changes of concrete material system characteristics and environmental requirements is a major development direction. In addition, toughness enhancement and self-healing admixtures are still in the research stage, and the key properties are still unclear. How to realize the application needs, further reveal the structure-activity relationship of key materials and achieve the improvement of toughness and self-healing properties is a problem worthy of in-depth study.

2) The control of concrete microstructure is a key to improving the durability of concrete. Air entraining agent, pore hydrophobic agent and nano-pore compacting agent are effective technical means to enhance concrete microstructure, which can solve the durability failure problem of concrete under freeze-thaw, sulfate attack and chloride ion attack. However, for coupled corrosion environment, there are still insufficient mutual adaptability of various admixtures applied together, and a further research is needed. In addition, the relations among air entrainment agent, pore hydrophobic agent, nano densifier, cement hydration, stable regulation/optimization of pore structure, and the resulting durability impact mechanism are still unclear, which need to be further investigated.

3) The improvement of rust resistance of steel bars is a fundamental to the improvement of structural concrete durability. Inorganic and organic rust inhibitors are important components of rust inhibitors, and the reasonable use of different kinds of rust inhibitors is a key to achieve the improvement of rust resistance performance of steel bars in complex systems. The corrosion protection and repair of structural concrete can be improved via different application methods such as internal mixing, external coating, electromigration and pressure penetration. The future development direction of rust inhibitors can be green and intelligent, but it still needs to be further studied in combination with practical applications.

Although the durability of concrete is extremely complex, admixtures have some technical advantages in improving the durability of concrete. In the future, it is necessary to further analyze the micro-action mechanism and structure-activity relationship of admixtures, and propose an effective method of structural design and preparation of admixtures by theoretical calculation (i.e., molecular simulation, artificial intelligence and other theoretical analysis). Also, slow and controlled release technologies such as microcapsule coating, layered and porous material loading are used with the characteristics of cement hydration to enhance the durability and improve the adaptability of admixtures to cement concrete, thus realizing the efficient use of admixtures in concrete systems at regular and fixed points, avoiding the influence of admixtures on cement hydration, microstructure formation and long-term performance, and achieving an accurate control of structural concrete durability throughout the life cycle.