Effects of CCCW on properties of cement-based materials: A review

The cementitious capillary crystalline waterproofing materials (CCCW), which can generate crystals filling the cracks and pores of concrete by means of the permeation and crystallization of its internal active chemicals. The main action mechanisms of active chemicals in cement-based materials are precipitation reaction and complexation-precipitation reaction. However, both of them show defects in explaining the long-term waterproofing effect of concrete. One solution is to combine the two mechanisms, while the dominant one between them seems different and unclear in different environments. The repair effects of CCCW on concrete were affected by several factors, including the usage methods, material composition and curing environment, etc. It was generally believed that CCCW can better promote the structural strength when used as admixtures than as coatings and water immersion curing is the most favorable curing method. The existing evaluation methods of CCCW are suitable for different conditions but still have some limitations in reflecting the effects of crack repair, together with a difficulty to introduce suitable artificial cracks. It is necessary to standardize and improve the existing methods. In a word, numerous problems still exist in the study of CCCW. In order to have a clear and comprehensive understanding of CCCW, the action mechanisms of CCCW in cement-based materials, the impacts of CCCW on the performance of concrete, the evaluation methods of crack repair effects and cost analyses of CCCW are reviewed deeply. Some suggestions on the application and potential research directions of CCCW are also put forward.