Structural material

It has a relatively low melting point, good fluidity, castability, excellent machinability and wear resistance.

Though almost entirely replaced by steel in building structures, cast irons have become an engineering material with a wide range of applications, including pipes, machine and car parts.

Cast iron retains high strength in fires, despite its low melting point.

Steel is used extremely widely in all types of structures, due to its relatively low cost, high strength-to-weight ratio and speed of construction.

Steel is a ductile material, which will behave elastically until it reaches yield (point 2 on the stress–strain curve), when it becomes plastic and will fail in a ductile manner (large strains, or extensions, before fracture at point 3 on the curve).

Concrete is used extremely widely in building and civil engineering structures, due to its low cost, flexibility, durability, and high strength.

It is placed in a mould, or form, as a liquid, and then it sets (goes off), due to a chemical reaction between the water and cement.

Its colour, quality, and finish depend upon the complexity of the structure, the material used for the form, and the skill of the worker.

It is usually taken as approximately 25 GPa for long-term loads once it has attained its full strength (usually considered to be at 28 days after casting).

Due to its weakness in tension capacity, concrete will fail suddenly and in brittle manner under flexural (bending) or tensile force unless adequately reinforced with steel.

[1][2] It can be used to produce beams, floors or bridges with a longer span than is practical with ordinary reinforced concrete.

Prestressing tendons (generally of high tensile steel cable or rods) are used to provide a clamping load which produces a compressive stress that offsets the tensile stress that the concrete compression member would otherwise experience due to a bending load.

Aluminium is used in some building structures (mainly in facades) and very widely in aircraft engineering because of its good strength to weight ratio.

Since the widespread use of concrete, stone is rarely used as a primary structural material, often only appearing as a cladding, because of its cost and the high skills needed to produce it.

Masonry, like concrete, has good sound insulation properties and high thermal mass, but is generally less energy intensive to produce.

Timber is the oldest of structural materials, and though mainly supplanted by steel, masonry and concrete, it is still used in a significant number of buildings.

Wood is strong in tension and compression but can be weak in bending due to its fibrous structure.