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What Is GRC?
GRC stands for “Glassfiber Reinforced Cement/Concrete.” It is a composite material made from Portland cement combined with alkali-resistant glass fibers randomly distributed throughout the sand/cement matrix. The fibers serve a similar purpose to steel reinforcement in reinforced concrete, primarily placed in areas subjected to tensile stress. Because glass fibers add flexural, tensile, and load-bearing strength, architectural panels made from GRC are strong, durable, and lightweight.
Where Are GRC Panels Used?
GRC panels are widely used as exterior façade materials in the construction or renovation of various types of commercial and institutional buildings.
GRC is available as wall units, window wall units, spandrels, mullions, and column claddings, as well as for fascia panels, soffits, parapets, sun screens, mansard roofs, and interior feature panels.
Each panel is custom-designed for a specific application, and its largest dimensions can be either vertical or horizontal. Panels can reach sizes of 10 m² or even larger, reducing production, transportation, and installation costs
How Are GRC Panels Produced?
The panels are produced by hand-spraying a mixture of cement/sand aggregate and chopped glass fibers into molds of the desired size and shape.
A surface layer consisting only of cement/sand slurry combined with selected admixtures is sprayed into the mold to achieve the desired final appearance and to protect the glass fibers at the surface. Several backing layers of concrete paste and glass fiber are then applied, with the surface mixture deposited in stages to a thickness of no less than 0.5 cm per layer. Each layer is compacted using brushes or hand rollers to consolidate the layers.
A light steel frame, welded into reinforcement and track framing, is then positioned on the finished molded panel and connected to the back of the cement skin using flexible L-shaped anchors
Why Do We Use Steel Stud Framing?
The lightweight steel reinforcement frame functions to add stiffness and rigidity to the thin concrete wall skin, allowing large panels to be fabricated, shaped, and transported to the job site without damage.
The flexible anchors do not penetrate the GRC skin at every point; instead, they allow the skin to move independently from the steel frame, reducing internal stresses that may occur due to differential expansion and contraction between the concrete skin and the steel frame.
At the installation site, the frame serves as a connection point for welding or panel joints to the building structure. This system is also commonly applied to interior wall surfaces, such as drywall, while providing space for insulation, electrical wiring, mechanical ducts, and communication lines.
How Does GRC Compare to Precast Concrete?
GRC is a cement-based material that is more elastic and denser than precast concrete. The cement-to-sand ratio for GRC is 1:1, compared to 1:6 for precast concrete. The addition of glass fibers provides significant flexural strength to the thin skin and results in higher load-bearing capacity, as well as lower permeability to water and air than precast concrete.
GRC is used as a curtain wall (non-load-bearing) or exterior cladding, where panels function as enclosure elements rather than structural support. For applications requiring structural load-bearing support, precast concrete panels are a more suitable choice.
Why Do Installed GRC Panels Sometimes Appear Uneven (i.e., Streaked and Speckled)?
During installation, GRC panels are exposed to handling marks (from hands and molds), dirt and mud from transportation and on-site storage, welding fumes during installation, and adverse weather conditions.
In addition, natural efflorescence from the hydration of the cement matrix leaves streaks and deposits on the panel surfaces. Water absorption by the panels is non-uniform across their areas.
Once the building is fully sealed and the GRC panels are cleaned and dried, the panels become more uniform in appearance.
How Does the Weight of GRC Panels Compare to Precast Concrete Panels?
The cement and sand mixture in GRC panels supported by a steel pipe frame typically weighs between 5–8 kg/m² with a skin thickness of 1.5 cm. As the thickness and panel area increase, the weight will also increase. This weight does not include the load of the steel pipe material used as the supporting frame.
In comparison, precast panels with the same thickness of 1.5 cm weigh approximately 30–35 kg/m². This difference is due to the constituent materials of precast concrete, which include coarse aggregates (stone) and embedded steel reinforcement.
What Are the Advantages of Lightweight GRC Panels?
There are many advantages. In multi-story steel structures, a dramatic reduction in the amount of steel required for the building structure can be achieved. For example, in a 100,000 SF tower, GRC panels can reduce the building weight by more than 3,000 tons, thereby reducing the size, weight, and cost of the building foundation, footings, beams, and columns.
GRC panels are ideal for renovation or recladding of existing buildings because they add minimal additional load to the existing structure and foundations. In many cases, GRC panels can be installed directly over existing cladding with minimal impact on the building structure.
How Much Does GRC Cost & What Are the Installation Costs?
GRC panels are often priced on a cost-per-square-meter basis (Rp … /m²), or on an “FOB Job Site” basis (materials only), or as an “Installed” cost (materials and installation).
The material cost of GRC panels depends on several factors, including project size, panel complexity, and the repetition of profile shapes (i.e., reuse of molds for repeated forms).
Installation costs for GRC panels vary based on panel size, accessibility for creating connection points, ease of site access, and the availability and type of crane required