Concrete is reinforced to give it extra strength – without such reinforcement, many building projects would be impossible. Reinforced concrete can be used for many types of structures and components and can be made into almost any shape or size. The material is developed by incorporating steel reinforcement bars, plates or fibres into the traditional concrete mix.
Concrete reinforcement was first used in the mid 1800s by French building contractor Francois Coignet. His own house, built with reinforced concrete, still stands some 150 years after construction. The invention of reinforced concrete in the 19th century revolutionised the construction industry, and concrete became one of the world's most common and most important building materials.
Typically used for highways, retaining walls, sewerage tanks and concrete foundations, reinforced concrete provides extra tensile strength for heavy duty construction projects. The steel reinforcement gives added strength by taking up the tension stresses, while the concrete takes up the compression stresses; meaning the two materials act together as resisting forces.
The coefficient of thermal expansion of concrete is similar to that of steel, eliminating internal stresses due to differences in thermal expansion or contraction. In concrete reinforcement, the cement paste hardens and adapts to the surface details of the steel, meaning that any stress can be effectively passed between the two materials. Steel bars are often roughened or corrugated to further improve the bond between the concrete and steel. Adding alkaline producing Calcium carbonate causes a passivating film to form on the surface of the steel, making it much more resistant to corrosion than it would be in neutral or acidic conditions.