The ideal curing environment for precast concrete is climate controlled to allow precasting in any weather and to tightly control temperature and humidity to create optimal conditions. But large clear-span buildings with overhead cranes are expensive to build and individual large precast members would still require tarping for efficient curing.

Retractable enclosures

To improve their process, precast and prestressed concrete manufacturers across North America are increasingly turning to retractable enclosures that can provide a controlled environment superior to tarps. This equipment also provides building-like protection and curing predictability at just a fraction of the cost and footprint of permanent structures.

These lightweight, modular, retractable enclosures essentially serve as both a building and a tarp, at sizes as large as 60 feet wide and 25 feet high and with no length limit. With a rolling framework made of aluminum or steel, they have a telescoping aluminum frame, are designed for indoor or outdoor use, and do not require motors to deploy. The most rugged have a tear-resistant, flame-retardant, UV-protected vinyl shell with seams that are welded, not sewn. Tents can also be made with insulating material for greater energy efficiency but that restricts the ability to fold up.

Unlike tarps, retractable enclosures are custom-designed to meet the needs of a rugged, industrial environment. They not only protect precast concrete forms or curing areas from sun, rain, snow, and wind, but also enable precise control of humidity and temperature within a weatherproof, vaporproof barrier. This enables more predictable form curing times and a higher quality final product with virtually no stress cracks or imperfections, significantly reducing the rejection rate.

With retractable enclosures, significant savings can be achieved for a number of reasons. Since they can eliminate the need to construct a permanent building, capital expenses are drastically reduced. Retractable enclosures also reduce employee time spent covering and uncovering products, as one or two employees can operate the retractable enclosures by hand without additional equipment.

Since retractable enclosures also offer full overhead and side access when retracted, this allows a crane to hoist oversized forms such as girders when curing is complete, saving time and labor over permanent structures where this is not possible. Because they can be used indoors or out, they can be used as a mobile plant near the worksite of a project, if needed, minimizing product transport. Production downtimes are also reduced since the retractable enclosures allow production to continue virtually year-round, enabling consistent pouring and curing in hot or cold weather.