Water repellent chemistry creates a coating over the concrete and cement materials used in precast construction. The result benefits the building's durability, but the repellents must be diluted correctly first. Incorrect mixtures can do more harm than good. For walls, repellents are highly diluted with water themselves, while horizontal surfaces where extra water can pool require less dilution for effective application. When correctly sprayed on, these repellents have several benefits.
When the concrete is first cast, some water repellents and surface treatments are used during the curing stage. This keeps the concrete from drying out too quickly while protecting it from water vapor. Maintaining the correct level of moisture throughout the first several days of curing ensures that the concrete solidifies with maximum strength and durability, keeping the building strong.
When concrete is more fully cured, water repellents are used as sealants over the precast pieces. These repellents ward away not only water but also errant particles that might otherwise bond the concrete. Over time, the dust and grime would otherwise darken the concrete surface, especially near ground level, and lead to stains or patterns of dirt that would detract from the appearance.
In the long term, water repellents help protect the concrete from rain as well. With temperature changes, storms and other weather events, concrete can crack and chip away over time. The repellents keep moisture from entering deep enough to cause these problems. The repellents might need to be reapplied over time for maximum effectiveness, but can then help preserve concrete walls for a longer time than they would have otherwise.