Prestressed concrete is a type of concrete that has been subjected to compressive stress before it is loaded. This is achieved by introducing tensile forces into the concrete through the use of prestressing tendons, such as steel cables or wires. The prestressing force helps to counteract the tensile stresses that occur in the concrete when it is subjected to external loads, thereby improving its durability and resistance to cracking.

The book "Prestressed Concrete" by N Krishna Raju is a comprehensive guide to the design and construction of prestressed concrete structures. The book covers the fundamental principles of prestressed concrete, including the types of prestressing systems, the properties of materials, and the design of prestressed concrete members.