Encapsulated Admixtures with Temporary Coatings for Delayed Delivery of Core Material—Review

Encapsulated admixtures in concrete have emerged as a prospective material to be used in future constructions. The core material is temporarily protected by the shell material, which also prevents the core from reacting with the concrete environment. The shell can be made of a pH-sensitive material that can deliver the core material based on the pH of environment rather than through mechanical rupture. The initial high alkaline nature of the concrete (pH 13.5) during the hydration and subsequent pH reducing conditions (by the environmental factors) can be used to design the delivery time of the core material. The coatings can be used to deliver the core material either within a short period or after a long period. The delivery of the core material at a desirable time can be achieved by the selection of a suitable coating agent. Keywords: delayed delivery; encapsulation; microcapsules; pH changes; soluble coating.