2001

2001 Concrete Canoe Team

People often laugh when members of our team say that they are building a canoe out of concrete. Concrete is the most widely used building material in the world today. Concrete, unlike other materials such as steel, can be made from resources that are widely available on every continent. So, why are concrete canoes so inconceivable?

Concrete is usually perceived as being a heavy, rough material that would not ordinarily be suitable for construction of watercraft. But concrete has many characteristics that are well suited for the construction of boats, canoes or larger structures. Some of the examples of maritime construction using concrete are:

	Early Concrete Boats: A Frenchmen, Joseph-Louis Lambot patented wire-reinforced concrete boats in 1847. His boats were rowed around the lakes of private estates in France. One of reasons we are aware of his boats are because several of them have been found in recent years, on the bottom of the lakes that they sailed on.
	Ferro-cement pleasure craft: Ferro-cement, a type of concrete, has been successfully used in the construction of sailboats and motorcraft for many years. Beginning in 1945, Pier Luigi Nervi, an Italian engineer and architect, constructed a 150-ton ferrocement motor sailor, named Irene. Compared to construction standards at the time of construction, his ferro-cement hull weighed five percent less than a comparable wooden hull and cost 40 percent less. (http://idh.vita.org/pubs/docs/ufc.html)
	Floating Concrete Docks: During World War II, the shortage of steel resulted in the use of concrete for many types of construction. During the invasion of Normandy by the Allies, huge floating concrete docks were used for the unloading of heavy equipment. Today, concrete docks are used in many parts of the world and in many different sizes. Several companies supply modular precast floating concrete docks, while oil terminals in Alaska are often built using floating dock and concrete technology.
	Emergency Hull Repairs: Large ocean going ships often store cement and reinforcing wire in their holds, for the purpose of performing emergency repairs to hull penetrations. This concrete is undoubtedly of a fast setting (high heat of hydration) variety.

The historical use of concrete in maritime construction highlights the positive properties of concrete construction when applied to watercraft. Concrete is a highly formable, highly finishable material that can be used to construct complex curved shapes of a high quality. In concrete canoes, the hull is cast using male and/or female forms. Therefore, the quality of the hull shape is related to the form and not related to the concrete. The concrete is so finishable; it can be sanded to a surface that is as smooth as that of a fine German automobile.

History has also shown that the properties of concrete can be readily altered while maintaining cost and availability. In some cases, the chemical characteristics of the cement are altered to change the setting and strength development properties. This is true with concrete for the emergency repair of punctured hulls, where more tricalcium aluminate is added to the mix to promote early strength development. Our canoe this year incorporates a latex admixture, which changes the plastic properties of the concrete. In other situations, changing the characteristics of the aggregate makes the concrete significantly different. The concrete that is used in Cal's concrete canoes utilizes a lightweight aggregate, which lowers the unit weight of the concrete. In fact, our concrete is so light it actually floats in water!