Precast concrete is one or more types of concrete that incorporate reinforcing steel or other types of reinforcement to enhance the properties of the concrete. It has been used for many years as an economical construction material in one form or another in buildings, bridges and many other types of structures.

　　Much of its appeal to the field as a whole lies in the fact that the basic constituent materials-cement, sand, aggregate, water, and reinforcing steel-are available, and that it is possible to construct buildings using local labor and materials. In addition to being readily available, reinforced concrete is widely accepted because it can be molded into a shape or form, is inherently rigid, and is inherently fire resistant.

　　By protecting the steel reinforcement, reinforced concrete structures can be easier to use and last a long time, even in harsh climatic or environmental conditions. Reinforced concrete structures have also been shown to provide shelter from the potentially devastating effects of earthquakes, hurricanes, floods, and tornadoes. Based on these and other advantages, reinforced concrete can provide viable and cost-effective solutions in applications.

　　The focus of this book is on the design of reinforced concrete elements in building structures. Prestressed concrete is a technique that greatly increases the load-bearing capacity of concrete beams. Reinforcing bars in the lower part of the beam are subjected to tension before use and tension before the concrete is poured.

　　Once the concrete hardens, the tension on the reinforcement is released, thus exerting a built-in compressive force on the concrete. When a load is applied, the concrete is under less compression, but when the rebar is under a lot of stress, it doesn't become tension. Because the concrete is under compression, it is less likely to crack and break.