Post-Tensioning Concrete

Concrete is a uniquely versatile building material because of its readily available components, its ability to be placed as a liquid, and its high compression strength that allows it to support the tremendous weights required in construction. Despite these qualities, concrete alone does have a few drawbacks. Concrete can be brittle and weak against lateral forces like bending. Many techniques have been developed to improve concrete's performance in certain situations, such as post-tensioning. Post-tensioning is a technique used to reinforce concrete over unstable surfaces and across spans. It is a very safe concrete strengthening technique that has gained popularity in the last few decades as the technique has been perfected, with trainings and certifications standardized. In any project that calls for reinforced concrete, it is important to utilize a skilled concrete contracting team like The Conco Companies, the leading steel reinforcing concrete contractor in Portland.

Post-tensioning adds tension to steel cables in concrete, called tendons, after the curing process. The steel cables are encased in protective sheaths and placed after the formwork is built and before pouring the concrete. This allows for precise placement of the steel components in whatever shape is needed. Tendons are generally curved to produce counteracting forces to the concrete's service loads within the concrete. It is similar in principle to a bridge's arc which allows the service loads created by traffic to be distributed throughout the deck instead of an isolated area. The steel tendons include an anchorage assembly at both ends of the concrete block which allows for further tensioning. Once the concrete is poured and cured, the steel tendon is tightened and the anchorage assembly transfers that tensile force into forces compressing the concrete.

Pre- and post-tensioning are both variations of steel reinforced concrete. The unstressed variation, known as rebar, are steel bars placed throughout the concrete to improve its strength against non-compressive forces. Steel is a great reinforcing material precisely because of its strong tensile and torsion resistance. In pre- and post-tensioning systems, the steel is stretched to create tensile forces within the steel itself. Putting steel into tension places a constant compression force in the concrete. This technique leverages concrete's superior compressive force to improve its ability to handle non-compressive forces.

Post-tensioning allows engineers to create precise forces throughout a concrete block that can improve its performance in several situations. It reduces the amount of shrinkage cracking, the number and size of joints needed, and allows for longer, thinner concrete components. Post-tensioning can also be performed as part of a retrofit to strengthen existing concrete. These benefits have made post-tensioning a popular concrete strengthening method in bridge construction and other situations where longer and lighter concrete components enhance a project.

Conco’s mission is to be the best supplier of concrete services in the Western United States and to bring experience, expertise and quality to each project.  We continue to upgrade and expand facilities to better serve the growing market for public works projects, commercial, educational, parking structures, and other construction development.  Please contact us to learn more about our high-performance, precision-engineered fabricated rebar in the Portland area.