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ShareAugust 1, 2007 — Engineering students in the 20th annual American Society of Civil Engineers national concrete canoe competition, show off their latest canoe boat models. The concrete canoes float because a cubic foot of water weighs 62-point-4 pounds. A cubic foot of concrete composite concrete mix weighs 45-point-6 pounds -- thatýs almost 20 pounds lighter than water. Adding foam plus the concrete, then makes its lighter than water, so the whole canoe will float.
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- Engineering and Construction
- Construction
- Civil Engineering
- Nature of Water
- Sports Science
- Engineering
You think of concrete in our sidewalks, roads, and homes. But what about using it to make boats? When you're racing canoes made of concrete, it's not only about who's the fastest. How you build them is critical.
"In [our boat], we have a big block of foam that's contoured to the canoe," explained Skye Orvis, engineering student at California Polytechnic State University in San Luis Obispo, Calif.
"We used spider wire fishing line for reinforcement," said Brian Ferguson, engineering student at Western Kentucky University in Bowling Green, Ky.
In the 20th annual American Society of Civil Engineers national concrete canoe competition, teams of civil engineering students from the United States and Canada create what seems impossible -- a concrete floating vessel. But it's really nothing new.
"Concrete boats were used during World War II to transport troops back and forth to Europe," said Mike Shydlowski, BASF Race Consultant.
So how does concrete float?
"A cubic foot of water weighs 62-point-4 pounds. A cubic foot of our concrete composite concrete mix weighs 45-point-6 pounds -- something real close to that," Ferguson said.
That's almost 20 pounds lighter than water.
"If you add the foam plus the concrete, it's lighter than water so the whole canoe will float," Orvis said.
The races make up one-fourth of the total team score. The rest is based on skills like design and construction -- all preparation for the workplace.
"The teamwork required, the planning, the execution, the ability to manage a team of workers to present to practicing engineers, to be able to answer questions and sell their product," Shydlowski said.
This year's winner -- the University of Wisconsin-Madison. It's the fifth year in a row the school has won the "America's Cup of Civil Engineering."
BACKGROUND: The American Society of Civil Engineers sponsors an annual Concrete Canoe Competition. The event provides students of engineering with a practical application of the principles they learn in the classroom, along with important team and project management skills. It also challenges their knowledge, creativity, and stamina, while showcasing the versatility and durability of concrete as a building material. The 2007 event was held June 14-16 at the University of Washington in Seattle.
ABOUT THE COMPETITION: The annual concrete canoe competition dates back to late 1969, when engineering professor Clyde Kessler had his students build a canoe out of concrete. Since then, the event has expanded significant, with more than 200 universities participating each year in regional competitions. The winners of those move on to the national competition: the 'Olympics of civil engineering.' Teams must design their concrete canoes from scratch. The competition has four parts, each accounting for 25% of the final score: a technical paper, a technical presentation, a final product judging, and the concrete canoe race. The latter has five different events: a pair men and women's sprint, a pair men and women's slalom, and a four-person co-ed sprint.
WHATEVER FLOATS YOUR BOAT: Concrete canoes can float thanks to Archimedes' Principle. Archimedes was an ancient Greek mathematician who figured out that a body immersed in a fluid is pushed up by a force equal to the weight of the displaced fluid. This is called buoyancy; an object will float if its buoyancy is greater than its weight, and will sink if its weight is greater than its buoyancy. The shape and position of the body affects the strength of the force pushing up on the body. So a concrete canoe placed on end in water will sink because the weight of concrete is greater than that of the displaced water. However, in its normal position, the weight of the canoe depends on its total volume, since it includes all the air inside it. So the average weight is less than that of the water displaced, and the canoe floats.
WHAT IS CONCRETE? Concrete is a common construction material used in pavement, architectural structures, foundations, roads, parking structures, and brick/block walls. It consists of cement mixed with water and an aggregate (a space filler). Concrete used for sidewalks, for example, use larger, heavier aggregates like rocks, gravel, or sand, but for concrete canoes, the teams use very light materials: glass bubbles, fly-ash, or silica fume. Concrete hardens after mixing and placement because the water reacts with the cement -- a chemical process known as hydration -- and this bonds all the components together to create a stone-like material. About six billion cubic meters of concrete are made each year, and in the US it is a $35 billion industry that employs more than two million workers.
The American Society of Civil Engineers contributed to the information contained in the TV portion of this report.
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