What class of concrete is typically employed in pre-stressed concrete structures?

Pre-stressed concrete structures require specific material properties that ensure the concrete can withstand the high tensile stresses that occur after the pre-stressing process. Class P concrete is designed for pre-stressed applications and generally has a higher compressive strength compared to other classes of concrete. This is crucial because in pre-stressed concrete, high-strength concrete is needed to resist the induced stresses from the tensioning of the reinforcement (such as tendons or strands).

The mix design of Class P concrete typically includes a lower water-cement ratio and additives that enhance its performance under the conditions expected in pre-stressed applications. These characteristics help to achieve the desired strength and durability that are essential for the structural integrity and longevity of pre-stressed concrete components, such as beams and slabs.

Other classes, while useful for various applications, do not meet the specific requirements suited for pre-stressed concrete construction, which is focused on achieving high strength and stability.