What is GFRC?
GFRC stands for “Glass Fiber Reinforced Concrete”. It is a Portland cement based composite with alkalide resistant glass fibers randomly dispersed throughout the sand/cement matrix.
The fibers serve a purpose similar to the reinforcing steel in reinforced concrete, which is placed primarily in tensile stress areas. Because the glass fibers add flexural, tensile and impact strength, Architectural panels made from GFRC are strong, durable, and lightweight.
Where are GFRC Panels used?
GFRC panels are widely used as the exterior facade material in the construction or renovation of many types of commercial and institutional buildings.
They are available as wall units, window wall units, spandrels, mullions, and column covers, as well as for fascia panels, soffits, parapets, sunscreens, mansard roofs, and interior feature panels.
Each panel is custom designed for the specific application, and their largest dimension can be either vertical or horizontal. Panels 400 square feet and larger are possible, reducing production, shipping, and installation cost.
How are GFRC panels manufactured?
Panels are manufactured by hand spraying a cement/sand slurry and chopped glass fibers into forms of the desired size and shape.
An integrally colored face coat consisting of only the cement/sand slurry along with any desired decorative aggregates is sprayed into the form to provide the desired surface finish and appearance, and to protect against glass fibers on the surface. Several backing layers of slurry and glass fibers are then deposited over the face mix to a thickness of no less than 1/2″. Each layer is compacted with brushes or hand rollers to consolidate the layer.
A lightweight, welded steel stud & track frame is then positioned over the finished panel, and connected to the back of the cement skin via L-shaped flex anchors.
Why do we use a steel stud frame?
The steel stud frame adds rigidity and strength to the thin wall concrete skin, enabling large panels to be fabricated, de-molded, and shipped to the job site without damage.
The flex anchors do NOT penetrate the GFRC skin at any point, and they enable the skin to move independently of the steel frame, thereby reducing stresses in the material that might arise as the result of differential expansion and contraction between the concrete skin and the steel frame.
At the job site, the frame serves as a connection point for welding or bolting the panel to the building structure. It also provides a surface for applying the interior finish, such as drywall, as well as space for insulation, electrical, mechanical, and communication conduits.
How does GFRC compare to Precast concrete?
GFRC is both a more elastic and more dense cementitious material than precast concrete. The ratio of cement to sand for GFRC is 1:1, compared to 1:6 for precast concrete. The addition of glass-fibers to reinforce the skin results in significantly higher flexural and impact strength than precast, as well as lower permeability to water and air.
GFRC is a true curtain wall (non load-bearing) exterior cladding; where panels are required to supply structural support to the building (i.e., parking lots), precast panels are a better choice.
Why do newly installed GFRC panels sometimes look non-uniform (i.e., streaky and mottled)?
By the time they are finally installed, GFRC panels have been exposed to manhandling (hand and boot prints), dirt and mud from transportation and storage at the job site, welding fumes during installation, and bad weather.
In addition, the natural efflorescense from the hydration of the cement matrix leaves streaks and deposits at the surface of the panel. Absorption of water by the panel is non-uniform over its area.
When the building is finally sealed and the GFRC panels are cleaned and given the opportunity to dry out, the panels become increasingly uniform.
What kind of coatings can be used on GFRC panels?
GFRC panels are provided with an integral color and texture, so in many cases, no post-production coatings are required.
However, in the event that darker colors are required, the panels can be treated with clear sealers that simply darken the integral GFRC base color, or pigmented opaque sealers that provide the required color to the panel, regardless of the panel’s base color.
Pigmented coatings enable GFRC to have dense, saturated colors that the uncoated material cannot provide.
How does the weight of a GFRC panel compare with a Precast panel?
A typical cement & sand panel with steel stud frame backing will weigh between 12 and 15 PSF (lbs/square foot) with a nominal 3/4″ skin thickness. As the articulation of the panel’s profile increases, the weight will increase as well because the effective square footage of the panel has increased on the same frame size.
Use of a medium weight aggregate face mix will increase the panel weight to about 20 PSF. This compares to 70-75 PSF for the typical weight of 6″ precast panel fabrication.
What are the advantages of a light weight panel?
There are many advantages.
On multi-story steel structures, dramatic reductions in the amount of steel required in the building structure can be realized. For example, on a 100,000 SF tower, GFRC panels will reduce the building weight by more than 3,000 Tons, reducing the size, weight and cost of the building foundation, footings, beams and columns.
GFRC panels are ideal for renovation or recladding of existing buildings because they add a minimal superimposed load to the existing structure and foundations. In many cases, GFRC panels can be installed directly over old claddings with minimal impact to the building structure.
GFRC panels are widely used in seismic areas where the panel’s light weight and flexible connections to the building enable the skin to move during seismic events rather than collapse and fail.
Finally, GFRC panels can be installed using lighter, less expensive cranes, making installation both cheaper and faster.
How much does GFRC cost?
GFRC panels are often costed by the square foot ($/SF), on either an “FOB Job Site” (Materials only), or an “Installed” cost basis (Materials and Installation)
The Material cost of GFRC panels will depend on a number of factors, including the project size, the size and complexity of the panels, and the repetition of different skin profile forms (i.e., re-use of forms).
The Installation cost of GFRC panels will vary based on the average panel size, accessibility to building connection points, building site location (NYC is more expensive than Dallas), and availability and type of cranes required.
Can curved panels, or unusually shaped panel profiles be created economically?
Yes, especially if the shapes are repetitive. Although it costs more to create an original mold (or form) for complex shapes/profiles, if 10 to 20 castings can be made from a single mold, the cost is amortized over all of the castings, reducing the premium over a flat (unprofiled) panel to a nominal amount per casting
Can you have more than one color or texture on the same panel?
Yes, we can fabricate panels with multiple colors and textures.
However, by using different form finishes and sandblasting textures, we can often create widely different “looks”� on the same panel without changing the face mix.
This can give the effect of having multiple mixes on the same panel with little increase in cost.
How durable is GFRC in cold northern climates?
Very durable.
In freeze-thaw tests, samples showed only slight flaking after 300 cycles, compared to severe deterioration of unreinforced mortar after only 200 cycles. Laboratory tests show no surface deterioration after the equivalent of fifty (50) years service in weather typical of the northern U.S.
Because of its high density, water vapor permeance (~3) for GFRC is also very low compared to other concrete products.
How does GFRC perform under severe wind and rain conditions?
Extremely well.
A modified GFRC panel has been certified to the Dade County Category 4 Hurricane rating for wind-blown debris. In this test, the GFRC panel was able to absorb the impact of a 27 lb. 2×4″ stud propelled into it at 120 mph (80 fps) without failure.
The Harrahs Poydras Street hotel in New Orleans, which was under construction when Katrina hit, suffered very minimal damage to the installed GFRC panels, and only on floors where the building had not been sealed.
Over what distance can GFRC panels be shipped economically?
GFRC can typically be shipped economically anywhere in the continental USA.
This is because GFRC panels are lightweight, and can be fabricated as large panels (300+SF). A single flatbed truckload can typically carry from 1,200 to 1,500 square feet of GFRC, compared to about 400 square feet for precast panels. This greatly reduces the cost per square foot of shipping that has to be charged for transportation to the job site.
In fact, we have shipped panels outside the continental US to places such as the Bahamas and Angola (Africa). In such cases, overall panel size may need to be reduced to fit into available container sizes.
What square footage of GFRC can I reasonably expect to install on a daily basis with one erection crew?
It depends on several factors, including the panel size, access to the building, and access to the panel.
If the installation crew has inside access to the panel, they can install roughly 8-12 panels per shift; that would drop by 50% if the panels could only be installed from the outside (i.e., recladding application).
What limitations are there on choices of colors and textures? Will colors fade over time?
In choosing colors, keep in mind that darker colors have several disadvantages when compared to lighter colors.
Small differences in color from panel to panel are magnified with dark colors over large surface areas. Dark colors also tend to fade more over time than lighter colors, and show the effects of efflorescense more dramatically.,
Where vibrant, saturated colors are desired, we recommend that the GFRC panels be coated.
What kind of coatings can be used on GFRC panels?
GFRC panels are provided with an integral color and texture, so in many cases, no post-production coatings are required.
However, in the event that darker colors are required, the panels can be treated with clear sealers that simply darken the integral GFRC base color, or pigmented opaque sealers that provide the required color to the panel, regardless of the panel’s base color.
Pigmented coatings enable GFRC to have dense, saturated colors that the uncoated material cannot provide
What kind of maintenance and/or cleaning is needed on installed panels?
Maintenance is minimal; joints will need to be inspected on a regular basis, and recaulked on an as-needed basis, depending on climatic conditions.
Much like spandrel glass, GFRC panels can benefit from cleaning/washing on a regular basis to remove airborne contaminants. Frequency will depend on a number of factors, including panel color, air quality, and location.
Light colored, street level panels in urban environments may require more frequent cleaning to remove hand and boot prints, as well as air pollutants.
We are happy to provide guidelines and recommendations for panel cleaning on request.
What is your standard product warranty?
One year from substantial completion of the project
How can designing with GFRC panels help me to meet my LEEDs objectives?
GFRC window panels can be deeply recessed to provide natural and efficient sun shading at almost no cost premium compared to flush mounted windows. This reduces heat gain without reducing the amount or quality of light entering the building.
Integral steel stud framing can be pre-insulated at our factory, or at the job site to any desired R factor, and the thin wall concrete skin does not support combustion.
Lightweight panels use 80% less material than precast, and can be tranported economically throughout the USA
Click HERE to link to the PCI web site for a detailed discussion of how pre-cast concrete solutions can help your project meet LEEDs sustainability criteria, and improve the LEEDS rating of your projects.
Why is PCI certification important for me as a designer?
GFRC is a sprayed material, and the consistency and uniformity of its fabrication is highly dependent on good process and operator control, as well as material consistency from batch to batch.
To ensure this consistency, it is critical to adhere to a rigorous quality assurance process with respect to design, materials, mixing, fabrication and installation.
Rigorous quality audits are carried out by PCI-certified independent engineers 2-3 times annually without advance notice.
Although audits are rigorous and uncompromising, we feel that this 3rd party audit takes the onus off the specifier to become an expert, and gives the specifier confidence that individual panels will perform as advertised, fit-up as needed, and present a uniform color and texture to the world.
Does GFRC Cladding Systems recommend the use of factory applied sealants?
Though not required, sealants have several advantages that should be evaluated on a case-by-case basis.
On darker panels, sealants improve the panel-to-panel color uniformity, and help to stabilize the natural process of efflorescense over time.
Sealants also reduce the water and vapor permeability of the panel, and facilitate the removal of road dirt, hand and foot prints, welding fumes, or airborne contaminants deposited on the panel during transportation, handling, or installation.
