Why is U.S. Defense Secretary Leon Panetta concerned about concrete? Specifically, the strength of the mix used in Iran? That's because Iran is an earthquake zone, so its engineers have developed some of the toughest building materials in the world. Such materials could also be used to protect hidden nuclear installations from the artificial equivalent of small earthquakes, namely bunker-busting bombs.
Source: A May 3 posting by The Economist magazine. Read more.
National Ready Mixed Concrete Association