What is PRESTRESSED CONCRETE?
In basic terms, prestressed concrete is concrete in which high strength steel reinforcement is stretched and anchored to improve the structural capacity. The internal stress created by the embedded steel reinforcement greatly improves the performance and service of the product.
Why/when is it necessary to “STRESS” concrete?
In general, concrete does not have good tensile strength, however, it performs well under compression. A traditional analogy often used to explain the concept originated with Dr. Mangel who likened prestressing to stacking books side by side and placing pressure on both ends. The pressure exerted on the books creates so much strength that the books could be lifted as a single unit and could also support great loads on top without breaking apart. The very same concept is repeated with prestressed concrete products.
How does the process of PRESTRESSING occur?
The process of prestressing involves high strength steel tendons or “strand”, typically of low relaxation 270 kps type steel to be pulled to a predetermined, engineered spec and then concrete is cast over the strand and allowed to harden or cure. The strand is then cut at each end releasing the prestressing force into the product by way of its “bond” with the concrete. The internal force then allows the concrete to span greater distances and be loaded with greater weight.
What are some of the benefits of PRESTRESSING concrete?
Allows for the reduction in mild reinforcement
Aids in controlling cracking
Allows for longer spans in a single piece instead of the need for multiple pieces
Allows for greater load carrying capacity
What are some types of products that utilize PRESTRESSING?
Roadway pavement slabs
Take a look at the video below to see an in depth discussion on how prestressed beams are created and work.