The Economist has an interesting piece on how Iran's expertise in ultra high performance concrete is a security concern:
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....
A study published by the University of Tehran in 2008 looked at the ability of UHPC to withstand the impact of steel projectiles. These are not normally a problem during earthquakes. This study found that concrete which contained a high proportion of long steel fibres in its structure worked best. Another study, published back in 1995, showed that although the compressive strength of concrete was enhanced only slightly by the addition of polymer fibres, its impact resistance improved sevenfold.
Western countries, too, have been looking at the military uses of UHPC. An Australian study carried out between 2004 and 2006 confirmed that UHPC resists blasts as well as direct hits. The tests, carried out at Woomera (once the British empire’s equivalent of Cape Canaveral), involved a charge equivalent to six tonnes of TNT. This fractured panels made of UHPC, but did not shatter them. Nor did it shake free and throw out fragments, as would have happened had the test been carried out on normal concrete. In a military context, such shards flying around inside a bunker are a definite plus from the attackers’ point of view, but obviously not from the defenders’.