The How, When and What of Efflorescence on Precast Concrete

Efflorescence is white-colored crystalline deposit typically found on concrete surfaces. While it most commonly affects concrete masonry, its development can also be experienced in precast concrete—albeit to a lesser extent. Efflorescence on precast concrete can complicate the process of approving the final product as the finish may not match with the earlier approved mock-up samples in color and texture. That said, efflorescence is not a serious problem; it is temporary and it can be treated quite easily. The following article discusses how efflorescence forms, when it forms, and what you can do to remove it.

How does efflorescence form?

Efflorescence typically forms as a result of calcium hydroxide reacting with atmospheric carbon dioxide.

All concrete contains some calcium hydroxide formed in the hydration reaction of cement during the early stages of concrete curing. This calcium hydroxide is transported by water to the concrete surface through capillary action, where it combines with carbon dioxide from the air to produce insoluble calcium carbonate or efflorescence as we know it.

When does efflorescence form?   

Efflorescence can occur almost immediately or within a few months of product casting. Low temperatures, moist conditions and a slow rate of evaporation can accelerate the formation of efflorescence. This is why efflorescence problems are more commonly observed during winter where temperature is low and moisture tends to evaporate slowly.

What can you do to remove efflorescence?

Efflorescence on precast concrete usually disappears with normal weathering. In general, you can remove efflorescence by application of dry brushing and then flushing the concrete with water. If this does not work, you can try washing the surface with dilute muriatic acid of 5% to 10% strength. Be careful when applying the acid, for even slightly strong acid may change the color and texture of the concrete. Rest assured your precast concrete should look new and shiny.

Here, at Mohan’s Precast, we take great care when manufacturing precast concrete. This helps us minimize efflorescence problems and enables us to deliver the highest quality precast concrete products to our customers. Our precast concrete products are highly durable, resistant to external factors and designed to be aesthetically pleasing. Embellish your home or office exterior with Mohan’s Precast USA concrete additions. Get in touch with us today to discuss your precast concrete needs.