Bridge Materials
Bridges can be made of many different materials. Over time, people have found better and better materials to make bridges with. To see a visual for the evolution of bridge materials, go to the link below.
One of the first materials used to make bridges was wood. Wood is cheap, plentiful, and lightweight. However, it can rot or burn easily. Wood does not fare well when compressed or when in tension. Today’s bridges are not often made of wood.
Plastic is sometimes used in bridges. It is lightweight and can be made from recycled material. However, it is expensive to make. Plastic handles compression well, but not tension, as it tends to stretch.
Some bridges use brick as a material. Brick does not cost much, but is very heavy. Brick, like other stone-like materials, is great when it comes to compression. However, tension will easily break a brick.
Different types of concrete are used in bridges. Regular concrete is convenient because it is low-cost, fireproof, will not rust, and can be shaped before it is cured. It handles compression well, but not tension. Also, thermal expansion is hard on concrete.
Some concrete is reinforced with steel. This simply means that steel rods are put in the concrete mold before it is poured. The steel helps to hold the concrete together when tension acts on it.
Reinforced, prestressed concrete is even better at tension. This is because of the way it is made. Before concrete is poured, rods of steel are stretched within the mold. Then, the concrete is poured. When it is dry, the rods are released from being stretched. They help hold concrete together when tension acts on it, because they “want” to be stretched out again.
Stone was used in a lot of older bridges. While it cannot be shaped like concrete, it handles compression well. Stone does not fare well when in tension. Stone is best utilized in arches, where compression is the main force acting on the bridge.
Iron was a material in many bridges before steel was created. During the Industrial Revolution, cats iron became a hit with many bridge-builders. It handles compression well, but not tension.
Wrought iron came later. It can handle tension better than cast iron, and is still good at compression.
Steel came next, and is still used today. It may rust and does not handle extreme temperatures well, but it is better than iron in both compression and tension.
Plastic is sometimes used in bridges. It is lightweight and can be made from recycled material. However, it is expensive to make. Plastic handles compression well, but not tension, as it tends to stretch.
Some bridges use brick as a material. Brick does not cost much, but is very heavy. Brick, like other stone-like materials, is great when it comes to compression. However, tension will easily break a brick.
Different types of concrete are used in bridges. Regular concrete is convenient because it is low-cost, fireproof, will not rust, and can be shaped before it is cured. It handles compression well, but not tension. Also, thermal expansion is hard on concrete.
Some concrete is reinforced with steel. This simply means that steel rods are put in the concrete mold before it is poured. The steel helps to hold the concrete together when tension acts on it.
Reinforced, prestressed concrete is even better at tension. This is because of the way it is made. Before concrete is poured, rods of steel are stretched within the mold. Then, the concrete is poured. When it is dry, the rods are released from being stretched. They help hold concrete together when tension acts on it, because they “want” to be stretched out again.
Stone was used in a lot of older bridges. While it cannot be shaped like concrete, it handles compression well. Stone does not fare well when in tension. Stone is best utilized in arches, where compression is the main force acting on the bridge.
Iron was a material in many bridges before steel was created. During the Industrial Revolution, cats iron became a hit with many bridge-builders. It handles compression well, but not tension.
Wrought iron came later. It can handle tension better than cast iron, and is still good at compression.
Steel came next, and is still used today. It may rust and does not handle extreme temperatures well, but it is better than iron in both compression and tension.
Many different materials have been used to build bridges, and as new materials are found, the materials used to build bridges will change.