What’s Cool About Concrete?

Posted on January 20th, 2014

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By: MiaSci

The answer to the question in the title is: a whole lot more than you may think. Concrete is literally part of the structure and foundation of all the fun and fascinating experiences that will take place in and around our new, state-of-the-art  Patricia and Phillip Frost Museum of Science. But concrete itself is fascinating, and Hill International, Inc., Owner’s Representative for our new Museum project, shared some interesting tidbits with us to prove it.

Did you know that…

Concrete has been made since the days of the Greeks, Romans, and possibly even earlier? The Roman Pantheon, built in 126 AD still stands, and is the largest unreinforced concrete dome in the world.

Plain concrete is formed by mixing cement, fine aggregate (sand), coarse aggregate (crushed stone or gravel), and water.  When mixing these ingredients in specified proportions, a chemical reaction between the cement-water mix produces hardened concrete with properties similar to stone.

Similar to stone, concrete has a very high compressive strength (meaning it can withstand heavy loads), but its tensile strength (which refers to its ability to withstand being stretched or pulled) is barely 10% of its compressive capacity.  To remedy this, “reinforced concrete” was developed, which has embedded steel bars within the concrete in areas that would be subjected to tension.

How does that help reinforce the concrete?

It creates a material that combines the compressive strength of concrete, and the tensile strength of steel, and still allows it to be poured and molded into any shape or form needed for structural support. “Prestressing tendons” made of highly tensile steel cables can be added to the concrete for additional tensile strength.

What about the concrete at the Patricia and Phillip Frost Museum of Science?

The reinforced concrete compressive strength exceeds 5,000 pounds per square inch.

The tensile strength of the embedded steel reinforcement bars exceeds 60,000 pounds per square inch.

A network of prestressing tendons are being installed in the Gulf Stream Tank, which can resist up to 270,000 pounds for square inch.

Here are some current photos of concrete at our construction site, now that we all have a better appreciation for how cool concrete really is.

1

A concrete mixing truck pouring into a concrete pump, which will transport the concrete into the planetarium dome molds

3

Hose from pump truck pouring concrete into the forms in the planetarium (steel reinforcement bars can be seen in place)

5

Top view of the planetarium forming and concrete

7

Concrete finishing operations

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