Prestressed concrete
Prestressed concrete tensions steel so the section starts in compression before load. Pre-tensioned for precast planks; post-tensioned for slabs. AS 3600.
Ask Chalkline about this →Prestressed concrete is concrete where steel tendons are tensioned so the section starts in compression before any load arrives. Under load, that pre-compression offsets tensile stress, preventing cracking and allowing longer spans or thinner sections than reinforced concrete can reach with passive steel (verified 2026-06-11).
Pre-tensioned vs post-tensioned
Pre-tensioned means tendons are stressed before the concrete is cast, on a stressing bed in a factory. Once the concrete gains strength the tendons are released, compressing the element through bond. Common products: hollowcore floor planks, prestressed lintels, and bridge beams (verified 2026-06-11).
Post-tensioned means tendons run through ducts cast into the slab or beam on site. After the concrete hardens, a jack stresses the tendons against anchor plates at each end and they are locked off. Common applications: transfer slabs, commercial and multi-residential suspended decks, and some residential rafts on reactive sites (verified 2026-06-11).
Both methods are designed to AS 3600:2018, Concrete structures, the Australian Standard for reinforced and prestressed concrete. The structural engineer specifies tendon layout, stressing sequence, and hold-down points. A builder follows the engineer’s details exactly (verified 2026-06-11).
Never cut a PT slab without scanning first
Post-tensioned tendons are stressed to 70-80% of their ultimate tensile capacity and are invisible from the surface. Cutting, coring, or drilling through a tendon releases that stored energy and can cause structural failure or serious injury. Before any penetration into a PT slab, a GPR (ground-penetrating radar) scan is mandatory and work must not proceed until the scan is complete and a structural engineer has approved the location in writing (verified 2026-06-11).
Also known as: PT concrete, prestressed, post-tensioned concrete (PT), pre-tensioned concrete.
Category: Materials / Concrete.
Related
See also
References
- AS 3600:2018 Concrete structures, Standards Australia (verified 2026-06-11)
- Post-Tension Slab Penetrations: Scan Scope and Hold Points, SiteOps (verified 2026-06-11)
Last updated: 2026-06-11. Verified: 2026-06-11. Quarterly review for currency.