Precast concrete

Precast concrete is concrete cast or otherwise formed into finished elements at a location other than their final position in the works, then transported to site and installed. The defining advantage is a controlled environment: temperature, curing, mix batching and quality checks are all easier to govern in a shop than on an open site, and production is not interrupted by weather.

In practice

Most 3D-printed concrete produced commercially today is precast in this sense, because printing indoors removes the largest sources of variability from a process that is sensitive to temperature, wind and humidity. The constraints then become logistical rather than material: element size is limited by what can be lifted and transported legally, lifting points and handling stresses have to be designed for, and the joints between elements become the critical detail for both structure and water tightness. Dimensional tolerances also matter more than in cast-in-place work, because a printed element that is a few millimetres out cannot be adjusted at the interface the way poured concrete can.

Related terms

• In-situ printing — printing directly at the element's final position on site.
• Formwork-free construction — building without moulds, the main reason printed precast differs from cast precast.