Reinforced concrete (RC) is a composite material in which concrete's relatively low tensile
strength and ductility are counteracted by the inclusion of reinforcement having higher tensile
strength or ductility. The reinforcement is usually, though not necessarily, steel reinforcing bars
(rebar) and is usually embedded passively in the concrete before the concrete sets. Reinforcing
schemes are generally designed to resist tensile stresses in particular regions of the concrete that
might cause unacceptable cracking and/or structural failure. Modern reinforced concrete can contain
varied reinforcing materials made of steel, polymers or alternate composite material in conjunction
with rebar or not. Reinforced concrete may also be permanently stressed (in tension), so as to
improve the behaviour of the final structure under working loads. In the United States, the most
common methods of doing this are known as pre-tensioning and post-tensioning.

For a strong, ductile and durable construction the reinforcement needs to have the following
properties at least:
 High relative strength
 High toleration of tensile strain
 Good bond to the concrete, irrespective of pH, moisture, and similar factors
 Thermal compatibility, not causing unacceptable stresses in response to changing temperatures.
 Durability in the concrete environment, irrespective of corrosion or sustained stress for example.

Structural steel is a category of steel used for making construction materials in a variety of shapes.
Many structural steel shapes take the form of an elongated beam having a profile of a specific cross
section. Structural steel shapes, sizes, chemical composition, mechanical properties such as
strengths, storage practices, etc., are regulated by standards in most industrialized countries.
Most structural steel shapes, such as I-beams, have high second moments of area, which means
they are very stiff in respect to their cross-sectional area and thus can support a high load without
excessive sagging.