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Structuralaka: PSCaka: prestressed concrete

Pre-Stressed Concrete

In Plain English

Concrete that has been pre-compressed with steel tendons so it resists cracking under heavy loads.

Definition

Concrete in which internal compressive stresses are introduced before service loads are applied, counteracting the tensile stresses that would cause cracking under load. Pre-stressing is achieved by pre-tensioning (tensioning tendons before casting) or post-tensioning (tensioning after casting). Pre-stressed concrete enables longer spans, thinner sections, and improved durability compared to conventional reinforced concrete.

Why It Matters in Bidding

Pre-stressed members let designers achieve long clear spans with shallower sections, which can reduce floor-to-floor height, structural quantities, and overall building cost—factors an estimator must capture when comparing a pre-stressed scheme against cast-in-place. Pricing it correctly means accounting for specialized fabrication, tendon and stressing labor, and the sequencing constraints that affect schedule and cash flow. Misjudging whether work is pre- or post-tensioned can swing both the sub scope and the markup.

Example

Estimating a parking structure, the estimator solicits a precast/pre-stressed sub for the double-tee deck and a separate post-tensioning sub for the cast-in-place transfer slab, keeping the two scopes clearly split so neither is double-counted or missed at award.

Related Terms

Post-TensioningConcrete SlabSpanDead Load

Frequently Asked Questions

Pre-tensioning stresses the tendons before the concrete is cast, typically in a precast plant on a casting bed, so it ships as finished members. Post-tensioning stresses tendons after the concrete cures on site, usually in cast-in-place slabs. The two involve different subs, schedules, and cost structures, so estimators should bid them separately.
Pre-stressed precast members are fabricated off site, so lead time for shop drawings, approvals, and plant production drives the erection date. Post-tensioning adds on-site sequencing for stressing and grouting before forms can be stripped. Estimators should reflect these durations and any crane or erection crew costs in general conditions and the schedule.
Pre-tensioned members come from a precast/pre-stressed concrete plant that handles design, fabrication, and often erection under one subcontract. Post-tensioning is provided by a specialty PT subcontractor working with the concrete contractor. Confirm which party owns engineering, delivery, and erection so the scope and responsibility are clear at buyout.

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