If you give a nerd a canoe, he can float for a day. If you teach a nerd how to build a concrete canoe, he can float for a lifetime. Says Jennifer Pazdon (above, foreground), captain of the concrete canoe team at CMU: This is not your mother's concrete. Pazdon and other civil engineering students at Carnegie Mellon University are competing in the National Concrete Canoe Competition (sponsored by the American Society of Civil Engineers) to build and race these unlikely vessels. How do they float? "In order to decrease the unit weight of the mix, we incorporated EPS beads (expanded polystyrene) as one of our aggregates," says Pazdon, a senior. "It's like the stuff they make McDonald's cups out of." On Feb. 14 the students, after months of preparation, spent more than 12 hours pouring the hull of their 21-foot canoe, which can accommodate up to four people. "I designed the hull with a computer program and some genius," says Pazdon, "and then we had it milled at the same place that they make the forms that fit your TV so nicely in the packaging." CMU is entering the 16-year-old contest for the first time this year.