What is Precast, Prestressed Concrete?


Discover the benefits of precast, prestressed concrete to see why architects, engineers, and builders are turning to Tindall for their most complex projects.

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The Basics of Precast, Prestressed Concrete


What is precast concrete?

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Precast concrete is simply concrete that is cast in a location other than its final position. At Tindall, we cast our concrete on steel or wooden molds in one of our six manufacturing facilities. This type of environmentally controlled production is faster, safer, and more consistent than site-cast concrete. Our process ensures that each component meets stringent quality control standards before being shipped to the site for installation. Precast concrete is among the most versatile products in construction, combining a strong structure with the flexibility to use any combination of color, shape, or texture. These components help maximize a project’s potential while ensuring it is completed on time.

What is prestressed concrete?

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Prestressed concrete is a type of precast that uses prestressing strands in addition to conventional steel reinforcing. These strands, manufactured from high-strength steel, are pulled up to approximately 40,000 pounds/strand before the concrete is poured. After the concrete has achieved an acceptable strength, generally half of its final design strength, the strands are cut, and the prestress force (compression) is transferred into the concrete through bond. The piece is then removed from the form. This process strengthens the component, improves performance, and allows for longer spans with shallower members.

PCI Definitions of Precast, Prestressed Concrete


The Precast/Prestressed Concrete Institute (PCI), the technical institute and trade association for the precast industry, takes these explanations one step further by dividing precast, prestressed products into three categories.

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Structural Precast Concrete

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Structural Precast Concrete

Structural precast concrete includes beams, double tees, flat slabs, joists, purlins, girders, columns, spandrels, posts, braces, piers, piles, wall panels, and other types of components. Contract documents for each project should specifically identify all the components that are considered to be structural precast concrete. Some structural components may be left exposed in the structure for desired aesthetic appearance. Architectural treatments may be provided on the surfaces of the structural components, and should be specifically identified in the contract documents.

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Architectural Precast Concrete

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Architectural Precast Concrete

Architectural precast concrete is characterized by a higher standard of appearance uniformity with respect to surface details, color, and texture than structural precast concrete. Typical architectural precast concrete components fall into two groups: major primary components (including wall panels, window wall panels, and column covers) and other components considered decorative pieces and trim units (including copings, mullions, sills, and appurtenances such as benches and bollards).

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Prestressed Concrete

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Prestressed Concrete

Both structural and architectural precast concrete may be prestressed or nonprestressed. Prestressed concrete may be achieved using either pretensioning or post-tensioning methods. With pretensioning methods, the strands are tensioned before placing the concrete and after the concrete has gained adequate strength, the tension is released with the strands bonded to the concrete. With post-tensioning methods, the strands are tensions after the concrete has gained adequate strength and transfer of force to the concrete is through end plates. The strands may be either installed into a duct that can be grouted or encapsulated in a greased plastic shield to prevent bonding to the concrete.

Why use precast, prestressed concrete?


There are more than a few reasons why builders and contractors are embracing precast, prestressed concrete as their construction component of choice. Put simply, precast concrete is one of the most reliable and versatile products on the market today.

Design Flexibility
Consistent Performance
Inherent Resiliency
Unrivaled Efficiency

Precast Concrete Components


Every precast concrete structure is designed, manufactured, and built using a unique kit of parts. Check out what’s in our toolbox.

  • Double Tees
  • Spandrels
  • Wall Panels
  • Columns
  • Beams
  • Flat Slabs
  • Inverted Tee Beams
  • Stairs + Landings
  • Special Products

Precast Concrete Finishes


Think all precast concrete is gray? With endless design flexibility, precast can be manufactured with a wide range of color and finish options, from traditional masonry to modern and unique.

  • Pigments
  • Aggregates
  • Textures
  • Brick
  • Terra Cotta Tile
  • Formliner
  • Sandblast
  • Custom Forming

Frequently Asked Questions


When you want to learn more about precast concrete, it always helps to have an expert on your side. That's why Greg Force, president and CEO, PE, FPCI, F.ASCE, and Mary Ann Griggas-Smith, director of corporate engineering, PE, FPCI answer some of our most frequently heard questions.

When is the best time to get a precast contractor involved with my project?

Now.

What type of structures work well with precast construction?

Virtually any structure can be constructed using all precast components. However, certain structures benefit more from what total precast has to offer: cost competitiveness, schedule enhancement, durability, inherent fire resistance, thermal resistance, and sound insulation. The larger the footprint and more repetitive the layout, the more competitive precast concrete becomes. Because the cost of installation is largely dependent on the number of picks with the crane, the larger the pieces set in place, the greater the cost and schedule benefit achieved. Therefore, a multi-level structure will have less pieces per square foot, as one column or wall panel may support multiple floor levels. Employing the exterior walls for structural support eliminates the redundancy of perimeter framing such as steel columns and beams needed when panels are only used as cladding. In addition, these panels are fabricated without sacrificing aesthetics and include insulation capability. Modular components, such as those used in correctional facilities, are also very readily used as part of a total precast structure. These modules may be loadbearing and the exterior walls are able to be architecturally enhanced and contain rigid insulation making them an integral part of the building envelope.

How is the final structure built using precast components?

After the precast has been fabricated at the plant, the pieces are shipped on trailers to the site. The pieces are lifted into place using a crane according to an engineered sequence to ensure stability during construction. Pieces may be grouted, welded, or bolted to connect them to the foundation and each other. The precast drawings depict not only the construction sequence but the details of each connection of the final structure. The hardware necessary to build the structure is also prefabricated and shipped to the site ready for use. Tindall’s philosophy is to augment any third-party inspection with structural observation visits by our design engineers. This ensures that the structure has been built in accordance with the design intent.

What are scheduling and site safety benefits of precast concrete?

Precast concrete construction offers a wide range of scheduling and safety benefits. The components are manufactured in environmentally controlled production facilities. This ensures that each element meets stringent quality control standards prior to being shipped to the jobsite. The manufacturing process can be scheduled concurrent with the foundation and other on-site construction activity. Once delivered, elements are erected rapidly with minimal lifts, contributing to significantly shorter construction schedules. Additionally, precast construction provides quicker access for other trades to complete their work earlier, further expediting the overall construction process.

Precast eliminates the need for shoring, scaffolding and large installation crews, making site conditions substantially safer when compared to other construction processes. Precast also dramatically reduces the waste and debris, further reducing on-site safety hazards. This means that precast structures can be delivered and erected without substantial time investments for set up and maintenance of general conditions.

Is precast concrete sustainable? Can precast help achieve LEED certification?

Yes. Precast is widely considered to be one of the most sustainable construction materials on the market, making it a go-to option for many builders and architects seeking Leadership in Energy and Environmental Design (LEED) certification. Due to its low water-cement ratio, precast is incredibly durable, and the thermal mass of concrete provides inherent insulation that helps reduce the need for mechanically assisted heating and cooling.

Another important factor in precast’s sustainability is the reduction in construction waste on site. Precast construction helps reduce on-site debris, eliminates redundant members, and dramatically improves on-site safety by minimizing the size of the crew required to erect a structure.

Are exterior precast walls considered part of the structural system?

Yes. Precast wall panels can be designed as both load-bearing walls and shear walls to provide lateral resistance for wind or earthquake loads. Panels typically have a minimum wythe (exterior or interior concrete layer) thickness of 2 1/2 inches with greater thickness when needed for structural requirements. Panels may be designed as composite or non-composite, depending on the gravity load carrying requirements, as well as the applied wind forces.

Typically for load-bearing members, full composite action of the panel is desirable. The two wythes are tied together through the insulation layer to act together to resist loads. Thin wire steel trusses, as well as certain non-metallic proprietary systems, may be used to tie the panel together.

Experience and thermal imaging have both shown that a nominal amount of steel crossing the insulation boundary has minimal impact on thermal performance. Solid concrete sections are typically avoided especially between roof and floor. While tests have shown sufficient adhesion may exist between the concrete and the insulation to provide some degree of composite action, potential degradation of that interface suggests it shouldn’t be counted on for design purposes, as it may result in long-term serviceability issues.

Do exterior precast wall panels provide thermal resistance?

Yes. Insulated walls are often a key component of thermally efficient building envelopes. Precast walls, with their high thermal mass, have an advantage over lighter-weight materials due to the ability to store and release heat as the temperature fluctuates. This is recognized in the International Energy Conservation Code, the insulation R-value requirement for mass walls is less than other buildings due to their ability to store and release heat.

Wall panels with rigid insulation between two layers of concrete provide superior thermal performance by incorporating the required insulation in the exterior skin of the building. High R-values are achievable based on the type and thickness of insulation used.

In addition, these walls reduce schedule time because the insulation is installed in the panels rather than being applied by another trade.

Are there advantages to using a precast floor system as part of total precast construction?

Yes. The major advantage of utilizing a precast floor system is the benefit provided by the prestressed, precast elements themselves. They achieve longer spans and carry greater loads at shallower depths than other floor systems. These members also have inherent fire resistance, noise reduction, and vibration damping characteristics superior to most other materials.

Another major advantage of using a precast floor is the schedule time gained by having the floor members installed at the same time as the exterior precast facade and interior framing. The speed of precast construction is vastly superior to other types of construction. Reducing coordination by using a sole provider for the structure is another benefit to the design and construction team.

Does precast sound transmission class, STC, compare favorably to other building materials?

Yes. Weight is concrete’s greatest asset in reducing the intensity of the vibration produced by airborne sound from one side of the member to the other. The member stiffness and vibration damping capability are other factors that make concrete a superior construction material as it pertains to STC.

Precast walls and floors generally do not need additional treatments to provide adequate sound insulation. Charts and graphs showing results of acoustical tests of both airborne sound and impact insulation of various precast components are available in the PCI Design Handbook.

Can material for mechanical, electrical, and plumbing be cast into precast at the manufacturing plant?

Yes. When the precaster is brought on board in the early stages of design, a significant level of accommodation can be made for cast in items and blockouts in the precast members. This is especially evident in design-build projects, where a team of subcontractors works with the general contractor/construction manager and their designers to plan for cast in openings, electrical conduit and boxes, drains, and other items required. By doing this as part of the prefabrication of the structural components, significant time and expense can be saved over performing this work on site. Prestressed, precast members are typically cast on long forms so repetition is key to getting the most out of this approach. Engaging the precaster and MEP contractors as early as possible will provide the most cost-effective solution.

Are there members that will span farther and support heavier loads than the standard double tee?

Yes. One member that may be used is a Bulb T which Tindall has used for roof spans of approximately 100 feet with a member only 28 inches deep. The Bulb T resembles a double tee with an enlarged “bulb” at the bottom of the stem. This bulb allows for more prestressing strand lower in the member which increases the capacity and allowable spans. Another member that may be used is a deep double tee. Double tees with depths of up to 4’-0” have been used for heavy loads such as those required for data centers and manufacturing. Both member types allow for large open areas unobstructed by columns.

Is precast concrete fire resistant?

Yes. Precast concrete components can be designed to meet any degree of fire resistance required by building code or project specifications. Unlike other building materials, concrete is non-combustible and does not appreciably lose strength under elevated temperatures.

As can be proven by code-approved empirical data or by calculation procedures, the steel reinforcing within the concrete, protected by the concrete cover, retains sufficient strength to support the design loads during a design fire. As defined by ASTM E-119, this is proof that the component meets the structural end-point criteria. The heat transmission end-point, or the ability of a component to inhibit temperature increase on the unexposed surface from exceeding a certain temperature gain from the side exposed to fire, is a function of the thickness and the type of aggregate used in the concrete. This information is readily available from graphs that show the thickness required for a given fire endurance by aggregate type, which have been derived from furnace tests per ASTM E-119.

Is precast concrete construction hurricane-proof?

Yes. For any type of construction, the more robust the material used to build the structure, the more capable it is to withstand the impact of weather events such as hurricanes or tornadoes. Precast structures are resilient. They not only remain standing through an event while protecting human life but also can quickly be placed back into service. The mass of a precast structure makes it very stable when resisting lateral forces, no matter the magnitude.

Each precast component is designed to withstand the localized forces, while the connections between the component are designed to tie the structure together. In addition to the direct pressure and the suction applied to the walls of a structure, precast is more capable of withstanding the upward suction on the roof, particularly compared to a steel deck roof.

Prestressing allows the individual components to absorb loads applied to the surface and regain most or all deflection experienced under load. Prestressing also helps provide resistance to wind-borne debris with minimal damage.

Can precast be designed for progressive collapse?

Yes. The two most common design methods for progressive collapse are Tie-Force and Alternate Path. Either method may be employed in total precast structures in much the same manner as cast-in-place concrete by adopting an emulative approach.

In the first, the building elements are tied together with tension ties, in accordance with Unified Facilities Criteria, to ensure the overall system has enhanced continuity, ductility, and structural redundancy. For a precast system, this is achieved with a poured in place topping containing the required amount and placement of reinforcing steel. In addition, the vertical elements are tied to the topping.

In the second method, the vertical load-bearing system must be capable of having one of the elements eliminated, while still supporting the structure to resist both localized and progressive level by level collapse. Either the floor/roof system must be sufficiently rigid to span the void created by the missing support element or the framing beams must be connected to accommodate the double span created by the elimination of the common support.

Benefits of Precast Concrete


Efficiency

Precast offers faster erection schedules, lower total installed costs, and a simpler design process compared to other traditional construction materials. Precast’s rapid construction also offers earlier interior access for other trades, further expediting schedules. Plus, Tindall uses recycled, regionally supplied, and low-emitting materials to help create environmentally friendly structures.

Resiliency

Tindall’s precast, prestressed concrete structures are built to last. Precast naturally resists numerous hazards, including fire, severe weather, flying debris, earthquakes, and even explosions. The durability of precast helps reduce operating costs and the need for routine maintenance. Precast also helps prevent mold growth, resulting in more consistent air quality.

Consistency

Tindall’s environmentally controlled manufacturing process ensures consistently defect-free products. This process also helps eliminate weather delays, lost productivity claims, and other disruptions that can bring conventional construction to a halt.

Versatility

Precast concrete offers nearly endless design and aesthetic flexibility. By using formliners, aggregates, pigmentations, acid etching, and a variety of other techniques, Tindall’s designers can create customized finishes, sizes, and configurations for any design. Tindall can even mimic historical finishes like stone and brick facades.

Safety

When it comes to construction, nothing is more important than the safety of everyone on the project site. Precast, prestressed concrete helps create significantly safer site conditions by reducing the number of necessary workers, reducing the need for scaffolding, and offering swifter erection schedules.

Tindall’s Capabilities


Total Precast Structures

PCI defines total precast structures as any structure that’s substantial core and shell are comprised of precast components. In other words: If a structure is made almost entirely of precast, prestressed concrete, it’s total precast. This type of construction provides a wide range of advantages for architects and builders, including design flexibility, faster schedules, and lower total costs. Total precast is an exceptional choice for mixed-use, residential, commercial, manufacturing, and institutional construction.

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T-SLAB™

The Tindall Superior Lightweight All-Purpose Beam (T-SLAB) is a revolutionary precast concrete floor system. This patented slab system uses an innovative manufacturing process and multiple concrete types to deliver a stronger, lighter, more versatile slab. See how the 100% precast T-SLAB is outperforming the competition.

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Custom Solutions

If you can’t find the precast, prestressed concrete solution you need for your project — Tindall has you covered. With a dedicated research and development team and more than 30 in-house registered professional engineers, Tindall can develop custom precast components for nearly any application.

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Tindall Knows Precast


Since 1963, the Tindall team has been pushing the boundaries of what’s possible with precast, prestressed concrete. We’re never satisfied with “good enough,” and we’re always on the search for better, safer, more innovative precast solutions. With six PCI-certified manufacturing facilities across the U.S. and thousands of projects under our belt, we’re ready to take on your most complex challenges. Come get to know our team.

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