Precast Durability

What makes precast so durable?

Well, I’m glad you asked, there are a lot of different factors that all contribute to the durability and longevity of precast concrete. The average lifetime of a piece is 50-100 years depending on the environment where the product is installed. Precast concrete in public spaces are subjected to all sorts of wears and tears, rain, sun, snow, vandalism, the list goes on.  As such precast technology has advanced to meet these challenges.

Permeability

One of the key factors in determining the lifespan of a product is the permeability of the concrete, or how easily fluids are able to penetrate it. This wikipedia article has more information on the definition of permeability in earth sciences. If too much water seeps into rock or concrete it can cause serious structural issues within the product. Many of our products are reinforced using galvanized rebar to reduce the effect of rust but if concrete is too permeable this rebar will rust and expand which will lead to cracks forming in the concrete, illustrated by this infographic from the NPCA.

Fig. 1 Permeability infographic

In environments where concrete is subjected to freezing temperatures a new problems arises with permeability, Freeze-Thaw, or Frost Weathering. Freeze-Thaw occurs when water seeps into concrete during warmer times of the year and then freezes when it gets cold again. As the water turns to ice the concrete is pushed apart causing cracks and breakages. Then when things warm up again the ice inside the concrete thaws the water once again seeps further into the concrete until it freezes again. So how do we solve this problem of permeability? Thanks to modern precasting technology special additives have been created to deal with the affects of water. Some additives provide micro waterways inside of the precast that allow water to flow through it without getting stuck inside the product. Other additives prevent water from seeping in all together. Cement.org classifies these additives as “Superplasticizers” that are reduce the water ratio of concrete by around 12-30% and help block water from ever entering the concrete in the first place.

Resistances

One of the reasons concrete, particularly precast, is so widely used is because it can be easily combined with different aggregates to resist stresses like abrasion, chemicals, ASR reactions, seawater corrosion, and sulfate attacks. All these problems can be dealt with using various different cemetitious materials. For example fly ash, which is a waste product of coal combustion, can be used in concrete to resist ASR reactions. 

Fig 2.   Fly Ash

Thanks for reading

In conclusion concrete is used is the perfect material for a variety of environments and applications because of its adaptability and longevity. Thanks for reading this article, we hope it helped clear up some of your questions and maybe you even learned a thing or two. Let us know what you think in the comments below or share our article on social media!