Post-tension concrete is a type of concrete reinforcement that utilizes steel-strands/cables known as “tendons” to apply a compressive force on a concrete structure once the concrete has gained a certain strength. This enables the creation of longer-lived and more resilient concrete structures compared to those constructed using traditional concrete reinforcements.

The process of building a post-tension concrete structure begins by grading the concrete placement area and installing the post-tension tendons. These tendons consist of steel strands, enclosed in a plastic covering, filled with antirust protective grease within the plastic covering. The tendons are securely anchored at both edges of the concrete structure. Once the tendons are properly positioned the concrete is poured and the tendons sit within the concrete structure. Next, after about a week after the concrete has been poured (time to tensioning depends on specific specs of the project), the tendons are tensioned/stretched with a hydraulic jack from one edge while continuing to be anchored on the other. On average, post-tension strands are stressed to a force of about 5000 PSI per strand. Compare this to a rebar solely sitting dormant in a concrete structure, as opposed to a post-tension stand constantly placing a compressive force in the concrete it reinforces.

A notable advantage of post-tension concrete is its ability to allow for thinner and more flexible concrete structures. Due to the compressive force provided by the tendons, less quantity of concrete is required to achieve a level of strength compared to conventional reinforced concrete structures. The utilization of post-tension concrete can lead to significant cost savings in certain projects and reduce the overall weight of concrete structures.

Compared to rebar reinforced concrete, post tension concrete offers increased resistance against cracking and deformation. By distributing compressive forces across a concrete structure, the steel tendons decrease the chances of cracks and deformations due to tensile forces. Does this sound a bit counterintuitive? Concrete is bad at tensile strength, meaning a force that pulls it apart can easily crack/break the concrete, but is good at compressive strength (squishing the concrete together). If we add a strong compressive force that the concrete can easily handle, when we try to pull the concrete apart, it’s a lot more difficult because the post-tension strands are compressing the concrete together. This quality makes post-tension concrete particularly suitable for bridges, parking garages and other structures that bear heavy loads and endure tensional environmental stress.

To summarize, post-tension concrete is a concrete reinforcement type that utilizes steel tendons to apply a compressive force to concrete once it has cured for a certain period (varies depending on concrete mix and project specifications). This method allows for the creation of longer-lived, more robust concrete structures than would be possible with conventional concrete reinforcements. Its increased strength, durability, and cost-savings where possible, have made it a popular concrete reinforcement in newer concrete construction projects.