Want quick responses to our most asked precast questions? Our blog series, “FAQ Fridays,” is designed to answer your most popular questions, organized by topic and product category. In Part 5 of this series, we discuss the sustainability of precast, prestressed concrete.
Due to the inherent sustainable qualities of precast concrete, the Precast/Prestressed Concrete Institute (PCI) believes that precast producers have a unique opportunity and obligation to participate in the sustainability movement by supporting green building practices and continually improving their plant practices to reduce their environmental impact.
As the voice of the precast concrete structures industry, PCI’s sustainability committee provides leadership with education and best practices for using precast concrete technology and in the plants. PCI oversees a certification program that ensures quality and standardizes practices for precast plants and erectors and has launched a sustainable plants program. A key initiative of PCI and its sustainability committee is the development of similar guidelines for sustainable practices and plant operations.
Is precast concrete a green building material?
Precast concrete contributes to green building practices in significant ways. The lower water-cement ratios possible with precast concrete (in the range of 0.36 to 0.38) mean that it can be extremely durable. The thermal mass of concrete allows the shifting of peak heating and cooling loads in a structure to help reduce mechanical-system requirements. Because precast concrete is factory-made, there is little waste created in the plant, most plants employ exact-batching technologies, and it reduces construction waste and debris on site and indoor air quality concerns. The load-carrying capacities, cross-sections optimization, and long spans made possible with precast concrete members eliminate redundant members, and concrete readily accommodates recycled content.
What steps are precast operations taking toward sustainability?
PCI Producer Members meet local and state ordinances and emissions requirements. Initiatives within the industry include:
- Use of local materials in all mixtures, including local aggregate resources
- Water reduction, reclamation, and recycling
- Reducing cement requirements by lowering water-cement ratios
- Admixtures such as hardening accelerators to eliminate applied heat in curing
- Use of self-consolidating concrete (SCC) for quicker placement, no vibration, and reduced surface defects
- Use of environmentally friendly thin brick in place of conventional brick
- Carbon-fiber reinforcement that allows lighter and larger concrete sections with less embedded energy and no corrosion
- Use of supplemental cementitious materials (SCMs) to reduce cement consumption; participation in Cool Climate Concrete
- Enclosed sandblasting facilities with 100% process-waste control
- Standardizing wood form parts for multiple reuse; recycling discarded forms into mulch or fuel
- Recycling all scrap steel and reinforcement
- Reducing and reusing product packaging received in facilities
Is precast concrete energy efficient?
Most definitely! The thermal mass of precast concrete absorbs and releases heat slowly, shifting air conditioning and heating loads to allow smaller, more efficient heating, ventilating, and air conditioning (HVAC) systems. Insulation is often used in architectural panels and sandwich wall panels to increase thermal efficiency, with continuous insulation (ci) in walls being possible. The resulting savings are significant, reducing heating and cooling costs by 25% or more in some cases.
Does precast concrete contain recycled materials?
Yes! Typically. Precast concrete's fresh and in-place performance can improve when several common industrial by-products are added. Fly ash, slag, and silica fume, which would otherwise go to landfills, can be incorporated into concrete as supplementary materials. These by-products can also reduce the amount of cement that is used in concrete. Reinforcement is typically made from recycled steel. Steel is one of the most recycled building materials and can be reused again and again. Insulation and connections within the precast concrete also contain recycled content.
Can precast concrete members be reused?
Precast concrete members are unique in that they are individually engineered products that can be disassembled and are well suited for adaptive re-use design. Designers can easily plan future additions to buildings, because the precast concrete components can be rearranged. Once removed, precast concrete members may be reused in other applications.
Precast concrete is also friendly to downcycling, in which building materials are broken down, because it comes apart with a minimum amount of energy and retains its original qualities. An example of downcycling would be the use of crushed precast concrete as aggregate in new concrete or as base materials for roads, sidewalks, or concrete slabs.
How can precast concrete contribute to project and client sustainability goals?
Precast checks the box in many areas of sustainability such as indoor environmental qualities of sound insulation and the thermal mass of concrete which can reduce mechanical system requirements and energy consumption.
- Precast jobsites produce little to no waste, requiring no laydown area or site storage, and they're safer with single source responsibility for the structure and building enclosure system.
- Precast provides passive fire protection. Concrete offers a noncombustible environment that helps curtail fire danger and confines the damage into smaller compartments. It provides up to a four-hour fire rating and passes a hose-stream pressure test, which minimizes damage from water. Smoke damage is also reduced because the walls and floors cannot ignite.
- In terms of resiliency and adaptability, precast concrete panels provide a long service life and opportunities to move and reuse panels to refurbish buildings rather than tearing them down. As an inherently non-emitting source of VOCs, precast concrete doesn't emit harmful chemicals or contaminants. Additionally the material is impervious to mold, mildew, and pest infestation.
- Precast concrete provides multi-hazard protection from storms, flying debris, and high winds, and it can be designed to protect against explosions and earthquakes.
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