When humans first began building structures, they used only the natural materials available to them. The earliest builders constructed their dwellings, bridges, and dams from stone, mud, and wood. Over time, new materials were found or created. Concrete and brick provided good substitutes for stone, given that they could be made on site and molded into the desired shape. Iron and, later, steel provided builders with a versatile material that was resistant to both compression and tension.
Despite obvious innovations, however, materials technology has not evolved to the point where one material fits all building applications. Even steel, with its impressive strength and versatility, has limited usefulness in some structures, and stone and wood are still some of the most important building materials used today.
In the decision to use one material over another, engineers consider many factors. Among these, strength, weight, and cost are some of the most important considerations. Dams, for example, certainly rely on good design features to hold back the trillions of gallons of water some reservoirs contain, but more importantly, they rely on immense weight. This requires materials -- like concrete -- that are dense and, because of the large volume needed, relatively cheap. Except as support inside reinforced concrete, steel is generally too expensive to be used as dam material.
Other structures or parts of structures call for different types of materials. Aluminum alloys, for example, are resistant to corrosion, very light, and as strong or stronger than steel. Because of their high cost, however, these substances are typically used only in applications for which steel is less suitable, such as the outer covering, or skin, of skyscrapers.
Which material seems to break most easily in tension? In compression? Make a survey of all the materials around you in the room. Can you find signs of wear and tear? Which parts look as though they are about to come apart, break, or fail in some way? Go on a "materials" scavenger hunt where you live. Can you find structures made out of the eight materials described in the materials lab? Why do you think each material was a good choice for that structure? What materials are used to build houses and apartment buildings where you live? Why do you think these materials were chosen? If you traveled to another location, do you think the buildings people live in would be made of different materials? Why or why not? Which materials would you choose to make 1) a bridge, 2) an office skyscraper, and 3) a dam wall? Give reasons for your choices.