Reinforced concrete combines concrete with reinforcement to make a structural material that can resist both compression and tension. This lesson introduces its components, the complementary roles of concrete and reinforcement, and the physical properties that allow them to act together.
Concrete is made from coarse and fine aggregates held in a hardened paste, usually formed when Portland cement reacts with water. The cement hydrates and binds the aggregates into a rigid mass. Concrete generally performs well under compression, but tension can break its microscopic structure and cause cracking.
All flashcards
What is reinforced concrete?
A composite material in which concrete is combined with reinforcement, commonly steel, to improve resistance to tension and other structural actions.
What is rebar?
Steel reinforcing bar embedded in concrete to help carry tensile forces.
Why is plain concrete commonly reinforced?
Concrete resists compression well but is relatively weak and brittle in tension, so reinforcement helps control cracking and carry tensile load.
What does bond do in reinforced concrete?
Bond transfers stress between the concrete and reinforcement, allowing them to deform together and act as a composite element.
Name three properties desirable in reinforcement.
High tensile strength, good bond with concrete, and durability in the concrete environment; thermal compatibility and tolerance of tensile strain are also important.
Quiz questions
In an under-reinforced beam, which event occurs before the concrete compression zone crushes?Answer: The tensile steel yields.
What is the main purpose of prestressing concrete before service loads are applied?Answer: To introduce compression that offsets some later tensile stress.
How can carbonation increase the risk of reinforcement corrosion?Answer: It lowers concrete pH and can remove steel's protective passive condition.
Compared with steel, what is a common design consideration for FRP reinforcement?Answer: Its lower stiffness can lead to greater member deflection.
What does development length provide for an embedded reinforcing bar?Answer: Enough embedment to develop the required bar stress through bond.