What is Architectural Precast Concrete?
When I tell people that I work for an architectural precast concrete company they usually look at me like I just said something to them in a foreign language. I get it. Before I started at Olympian Precast I worked for several cast-in-place concrete subcontractors, and I still had no idea what architectural precast concrete was.
Most everybody knows what concrete is. It’s that wonderful cocktail that uses the ingredients sand, rock, cement, and water. Over time this blend will become rock hard due to a chemical reaction that kicks off when these materials are mixed together.
Like any good cocktail, you can add other ingredients (called admixtures) to the mix to give it different qualities. Common types of admixtures found in architectural precast concrete are integral color, water reducers (makes concrete flowable without watering down the mix. Too much water in the mix has a negative effect on the chemical reaction), air entrainment (adds microscopic air pockets in the concrete that prevents cracking/spalling during freeze/thaw cycles), etc.
The two ways of pouring concrete are cast-in-place (CIP) and precast. Cast-in-place is when the formwork is built on the jobsite as a part of the structure of the building. The second is precast concrete where concrete is poured into formwork at an offsite manufacturing plant and are also finished offsite. Once the contractor is ready to have the precast pieces installed, they are loaded onto a trailer and shipped to the jobsite.
Precast concrete is cast indoors and isn’t affected by hot, cold, or wet weather. Also, by pouring indoors we are able to have quality control measures put in place that allow us to consistently produce high-quality precast concrete products.
That brings us to, architectural. This is just a big word that when used in this context means “good looking”. Architectural precast concrete is designed to make the building look like what the architect intended it for. Architectural precast concrete comes in a variety of shapes and sizes. Panels, wall caps, windowsills, columns, benches, stair treads, etc.
Appearance can vary depending on the cement color, color admixtures, color and size of sand and rock used in the mix. Colored concrete and aggregate usually brings the cost of the concrete up. We are also able to place brick or stone in the formwork to make a brick or stone clad precast panel.
Another aspect that affects the appearance of the architectural precast concrete is the finish. Most common finishes are smooth form, acid etch, or sandblast. Finishes add texture and consistency to the appearance of the precast piece, and are more costly than a smooth form finish.
Smooth form finish is what the precast looks like right out of the formwork. The surface will often appear blotchy with light and dark spots. For this reason, most smooth form precast is painted on the jobsite for a uniform appearance.
Acid etching is a process where we spray the surface of the precast with hot water and muriatic acid. The acid peels away the top layer of cement and reveals the sand used in the mix.
Sandblasting is just like it sounds, we blast the surface of the precast with air compressed sand and this removes the cement and sand on top and reveals the rock in the mix. The depth of sandblasting will determine how much of the rock is exposed.
So now you know the secret, architectural precast concrete is just good looking hard stuff made inside a building. And after everything is installed on your project you are left with a resilient, high-quality product fabricated to highlight a part of the architect's vision for the product.
If you would like to know more feel free to reach out to Clarke Jewell or Mike Yore at (425) 868-1922 or check out our website at www.olyprecast.com.