Introduction
ous (chopped) lengths. GFRC has been used for the past 30 years to produce many concrete products, especially thin architectural cladding panels, but also for ornamental Glass fiber reinforced concrete, also known as GFRC or GRC, is a type of concrete such as domes, statues, planters, and fountains. Recently, decorative fiber-reinforced concrete. Glass fiber concretes are mainly used in exterior concrete artisans have discovered the benefits of GFRC for decorative panels building façade panels and as architectural precast concrete. Somewhat sim(such as fireplace surrounds), concrete countertops, and artificial rock work. ilar materials are fiber cement siding and cement boards.
0.1
GRC has been used for over 30 years in several construction elements, mainly GFRC is a specialized form of concrete with many applications. It can be nonstructural ones, like facade panels (about 80% of the GRC production), effectively used to createpiping for sanitation network systems, decorative nonrecoverable formwork etc. Façade wall panels Fireplace surrounds There is virtually no limit to the shape or profile that can be created in a vari Vanity tops ety of smooth, profiled or textural finishes. Moulds can be created to replicate Concrete countertops the most complex of profiles in restoration, renovation and new construction. Support systems can be adapted to meet the demand for unitised off site construction.
What is GFRC?
GFRC is similar to chopped fiberglass, although much weaker. It’s made by combining a mixture of fine sand, cement, polymer (usually an acrylic polymer), water, other admixtures and alkali-resistant glass fibers. Glass fiber-reinforced concrete consists of high-strength glass fiber embedded in a cementitious matrix. In this form, both fibers and matrix retain their physical and chemical identities, while offering a synergism: a combination of properties that cannot be achieved with either of the components acting alone. In general, fibers are the principal load-carrying members, while the surrounding matrix keeps them in the desired locations and orientation, acting as a load transfer medium between the fibers and protecting them from environmental damage. In fact, the fibers provide reinforcement for the matrix and other useful functions in fiber-reinforced composite materials. Glass fibers can be incorporated into a matrix either in continuous or discontinu-
Fig 1.1 GRC
Fig 1.2 Images
members being used as decorative railings thus reducing the overall weight of the structure
of Zaha Hadid’s Heydar Aliyev Cultural Centre pre and post construction, using glass reinforced concrete as a cladding material
0.2
Benefits
6) Toughness: GFRC doesn’t crack easily-it can be cut without chipping. Surface finish: Because it is sprayed on, the surface has no bugholes or voids.
There are lots of good reasons to use GFRC for thin sections of concrete:
7) Adaptability: Sprayed or poured into a mold, GFRC can adapt to nearly any complex shape, from rocks to fine ornamental details.
1) Lighter weight: With GFRC, concrete can be cast in thinner sections and is therefore as much as 75% lighter than similar pieces cast with traditional 8) Durability: According to ACI 544.1R-96, State of the Art Report on Ficoncrete. An artificial rock made with GFRC will weigh a small fraction ber Reinforced Concrete, “The strength of fully-aged GFRC composites will of what a real rock of similar proportions would weigh, allowing for lighter decrease to about 40 percent of the initial strength prior to aging.” Michael foundations and reduced shipping cost. Driver, division manager with Nippon Electric Glass, a major manufacturer of AR glass fibers, disagrees. “There’s never a durability issue. Water can’t get 2) High strength: GFRC can have flexural strength as high as 4000 psi and it in-there are no cracks-and that’s a durable material. GFRC will outlast precast has a very high strength-to-weight ratio. concrete, cast stone, even some natural stone.” Durability has been increased through the use of low alkaline cements and pozzolans. 3) Reinforcement: Since GFRC is reinforced internally, there is no need for other kinds of reinforcement, which can be difficult to place into complex 9) Sustainable: Because it uses less cement than equivalent concrete and also shapes. often uses significant quantities of recycled materials (as a pozzolan), GFRC qualifies as sustainable. 4) Consolidation: For sprayed GFRC, no vibration is needed. For poured, GFRC, vibration or rollers are easy to use to achieve consolidation. 10) Cost: GFRC as a material, however, is much more expensive than conventional concrete on a pound-for-pound basis. But since the cross sections 5) Equipment: Expensive equipment is not needed for poured or vibrated can be so much thinner, that cost is overcome in most decorative elements. GFRC with a face coat; for sprayed GFRC, equipment generally costs about $10,000.
Fig 2.2 GRC
panels cast and ready for fixing
Fig 2.3 GRC
decorative element
Fig 2.4 GRC
Fig 2.1 Decorative
colums made from GRC so as to reduce the overall weight of the structure and omit unnecessary dead load
used as cladding on the entire building. This allows for a lot of creativity in terms of facade designs
0.3
Manufacture
Glass fibre Reinforced concrete (GRC) is generally manufactured by either the “spray” process or the “premix” vibration casting process. The method chosen is normally dictated by factors such as strength requirements, size of mould, architects specification etc. As a general rule, larger items, such as building cladding panels, are normally “sprayed” whereas small items are manufactured from “premix” GRC. Sprayed GRC is generally stronger than premix vibration cast GRC. The reasons for this are firstly that with sprayed GRC it is possible to achieve a fibre content of 5% - 6% whereas premix GRC is limited to around 3% - 3.5%. Secondly, Sprayed GRC has a lower water content than Premix GRC.
Fig 3.1 A
typical handspray method of casting GRC
Typical mix designs for sprayed and premix GRC materials are as follows: Sprayed GRC Premix GRC Sand* 50kg 50kg Cement 50kg 50kg Water+ 15-17 ltr 17-18 ltr Plasticiser+ to manufacturers instructions Polymer+ optional optional Fibre+ 4-6% by weight 2-3.5% of weight *The sand used should have a particle size not exceeding approximately 1mm and should be well graded. Material passing sieve No. 100 should not exceed 10%. The sand should preferably be dry. **Dependant on type of fibre and property requirements. +The water/admixture/polymer content will need to be adjusted according to materials.
Sprayed GRC
Premix GRC
• The water and admixture (and polymer if used) are placed in a "high shear mixer" and the sand/cement are slowly added until a smooth creamy slurry is achieved. The consistency of the slurry can be checked using a simple slump test kit. Mixing time is about 1 - 2 minutes. • When ready the mix is transferred to a "pump/spray unit". The pump conveys the slurry at a regulated rate of flow to the spray gun. At the spray gun fibre, in the form of a roving, is chopped to a length of approximately 32mm and added to the slurry. The two materials are projected onto the mould surface using an air supply from a compressor. • The GRC material is sprayed and built up in thin layers until the required thickness is achieved - normally 10 - 15mm. Simple hand rollers are used to compact the material between layers. • The product is left in the mould and covered with polythene to prevent moisture loss until the next day. The product is then demoulded. • After demoulding the units are covered with polythene and allowed to cure for approximately 7 days. Alternatively, if a polymer curing compound is used in the mix the units can be exposed to the atmosphere immediately although it is advisable to keep them protected from direct sunlight or severe external conditions for a day or two. Reference should be made to the Polymer Supplier's instructions.
• The sand and cement are mixed dry and then the water/admixture and polymer (if used) are added. Generally a two speed slurry/fibre blender mixer is used. With this type of mixer, the fast speed is designed to create a smooth creamy slurry. This takes about 1 - 2 minutes. The mixer is then switched to slow speed and fibre in the form of chopped strand (length approximately 13mm) is added slowly. The fibre is blended into the mix for approximately 1 minute. • Once the mix is ready, it is poured into moulds which are vibrated using a vibrating table. • The product is left in the mould to set and is covered with polythene sheet to prevent moisture loss. The product is demoulded the next day. • After demoulding the products are cured under polythene sheets to maintain moist conditionsfor approximately 7days. Alternatively a polymer curing compound can be used as described for the sprayed process.
0.4
Design Ideas
The use of GFRC mixes has opened up a plethora of new design possibilities for contractors who make concrete countertops, fireplace surrounds, wall panels, furniture, and other decorative elements. Because GFRC is significantly lighter in weight and higher in tensile strength than conventional concrete, countertop slabs can be made without seams and span greater lengths. GFRC can be cast using decorative form liners to create architectural wall panels as thin and light as standard wood paneling while permitting more flexibility in shape, color, and texture. GFRC fireplace surrounds can span from floor to ceiling without requiring special reinforcement, and hearths and mantles can extend from wall to wall or be cantilevered to appear as if floating on air. GFRC can even be used outdoors to make artificial rock formations, permitting the creation of dramatic rock and waterscapes without the need to haul in heavy boulders.
Fig 4.1 GRC
decorative element cast and then shaped with the help of moulds
GFRC offers the same decorative versatility as conventional concrete. It can be formed into nearly any shape and stained or integrally colored. Various tints of gray, white, and buff can be achieved by using colored cements or pigments. The surface finish can be lightly textured or polished smooth to expose the aggregate. And GFRC can be seeded with colored decorative glass or stone to create granite-like effects.
G F RC c l a d d i n g
Construction 0.5 Effect of Fibres in Concrete GFRC cladding panels are erected on site by teams trained in safe handling and installation. The lighter - They control plastic shrinkage, cracking and drying shrinkage cracking weight of the panels makes installation simpler - They also lower the permeability of concrete and thus reduce bleeding of water 0.7 Construction and faster. Often, panel - If the modulus of elasticity of fiber is higher than the matrix (concrete or can place mortar binder). they help to carry the load by increasing the tensile strength GFRC installation cladding panels aretake erected on of the material site by without teams trained in safe for handling the need - Some fibres reduce strength of concrete and installation. an external scaffolding. Withweight proper planning, The lighter of the panels makes 0.6 Types of Fibres installation simplerpanels and faster. the GFRC canOften, panel installation can take place withbe started while the - A-glass (close to normal glass) out the need for an external scaffolding. foundations are underway - C-glass (resist chemical attacks) and then delivered on With proper planning, the GFRC pana just-in-time basis, - E-glass (insulation to electricity) els can be started while the foundaallowing areas of tions are underwaylarge and then delivered - AE-glass (alkali resistance) on a just-in-time basis, allowing large the structure to be quickly areas of the structure to be quickly enThisinterior can allow - S-glass (high strength fibre) closed.enclosed. This can allow trades an earlyinterior start.` trades an early start. Fig 7.1 Installation
Questions? Contact us we are here to help. GFRC Cladding Panel Applications
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0.8
Panel Finishes and Facings
A wide range of cladding panel colour and textures are available GFRC cladding finish options include Cast stone or limestone Smooth concrete Exposed aggregate Form liners Wood grain texture Terra cotta glazes Brick or stone Other texture
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Panels may also include tow or more textures and finishes on a single panel. Cast in colours are obtained with selected cements and aggregates or with mineral pigments. Cladding panels may also be painted.
0.9
Panel Shapes and Sizes
Stone
Carved Stone
Brick
Coral
Panel Finishes and Facings A wide range of cladding panel colors and textures are available. GFRC cladding finish options include: • cast stone or • wood grain texture limestone • terra cotta glazes • smooth concrete • brick or stone Brick Coral Coral Terra CottaTerra Cotta • exposed aggregate • other textures • form liners Wood Grain
Stone Carved Stone Brick Carved Stone Stone GFRC is an extremely moldable material and this allows complex shapes to Marb be formed. Freeform curves, complex cornices and Facings intricate details can be inPaneland Finishes and Panel Finishes Facings corporated into the panels. Panels can range includeofreveals, window sills, copings, A wide cladding panel colors and A wide range of cladding panel colors and Panels may also include two or more textures and Can increase u soffits and specialDetails shapes.for GFRC Cladding Panels DTL7 textures are available. textures are available. finishes on a single panel. Cast in colors are obtained building “footp with selected cements and aggregates or with mineral Panel sizes are usually limited by transportation constraints. By using wide • The thinner cla GFRCfinish cladding finish options include: GFRC cladding options include: pigments. Cladding panels may also be painted. load orand lowProjections trailers, larger panelsPanels can be transported. These can allow 1 storyProfiles on GFRC insulation for a • c ast stone or • w ood grain texture high panels to be delivered vertically. • cast stone or • wood grain texture • Since they use limestone • terra cotta glazes Panel Shapes and Sizes limestone • terra cotta glazes the environme • smooth concrete • brick or stone GFRC is an extremely moldable material and this • smooth concrete • brick or stone government sp • exposed aggregate • other textures allows complex shapes to be formed. Freeform • exposed aggregate • other textures environmental • form liners curves, complex cornices and intricate details can • form liners Wood Grain Marble Stucco Wood Grain Marble Stucco compared to p be incorporated into the panels. Panels can include • The lighter GF reveals, window sills, copings, soffits and may also include twotextures or more textures and Can increase usable space Panels mayPanels also include two or more and Can increase usable floor spacefloor for aspecial givenfor a given on the building shapes. a single Castare in colors are obtained building “footprint”. This canrevenue. increase revenue. finishes onfinishes a singleon panel. Castpanel. in colors obtained building “footprint”. This can increase enormous amo Panel sizes are limited by transportation withcements selectedand cements and aggregates or with mineral • usually The thinner cladding allows more room for with selected aggregates or with mineral • The thinner cladding allows more room for structural steel constraints. By using wide load or lowefficient trailers, larger Cladding may also be painted. pigments. pigments. Cladding panels maypanels also be painted. a more insulation insulation for a morefor efficient building. building. • Simplified inst panels can be transported. These can allow 1 story• Since they use less material they reduce • S ince they use less material they reduce with the light w high panels to be delivered vertically. Panel Panel Shapes andShapes Sizes and Sizes the environmental impact. According to a the environmental impact. According to a cladding erect is an extremely moldableand material GFRC is anGFRC extremely moldable material this and this government government sponsored study, GFRC reduced sponsored study, GFRC reduced • Reduced trans allowsshapes complex shapes to be formed. FreeformThinner and Lighter Weight Panel Advantages allows complex to be formed. Freeform environmental impact by over 40% when environmental impact by over 40% when curves,cornices complexand cornices anddetails intricate curves, complex intricate candetails can• The thinner walls with GFRC cladding panels. compared to precast concrete panels. be incorporated into the panels. can include compared to precast concrete panels. be incorporated into the panels. Panels canPanels include • The lighter GFRC cladding reduces the load • The lighter GFRC cladding reduces the load reveals,sills, window sills,soffits copings, reveals, window copings, and soffits specialand special on the structure. buildings structure. This on the buildings save s t rThis o mcan ber g an acan r c save h i tan ectural prod shapes. shapes. enormous amount on foundations, slabs, enormous amount on foundations, slabs, greenville, tx 903.454.09 4400 oneal street sizes are usually by transportation Panel sizesPanel are usually limited by limited transportation structural steel and concrete. By using load or low trailers, largerstructural steel and concrete. info@4stromberg.com www.4stromberg.co constraints.constraints. By using wide load wide or low trailers, larger • Simplified installation and attachment details can be transported. allow 1 story• Simplified installation and attachment details panels canpanels be transported. These can These allow can 1 storyFig 9.1 GFRC cornice work Fig 9.2 The worker is securing a Fig 9.3 This hollow GFRC base being withweight the light weight can speed up the high panels to be vertically. delivered vertically. with the light panels canpanels speed up the high panels to be delivered in progress 115-pound GFRC curtain wall lowered into an excavation cladding cladding erection. panel to the building erection. frame by will support pad-mounted electrical DTL7Advantages Thinner and Lighter Weight Panel DTL8 • welding Reduced transportation costs. gear at approximately Thinner and Lighter Weight Panel Advantages • Reduced transportation costs. • The thinner walls with GFRC cladding panels. • The thinner walls with GFRC cladding panels. •
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1.0
Installation
GFRC cladding panels consist of a ½” to 1” thick concrete shell reinforced with glass fibers. The shell is attached to an integral 16 or 18 gauge galvanized steel stud frame. Typically the overall thickness of a panel is 6 ½” (including GFRC, airspace and stud frame). Studs are typically 24” on center. Closer stud spacing and larger studs may be necessary for longer spans. In some applications, tube steel or GFRC ribs may be used instead of the stud frame. Attachment of the GFRC shell or skin to the stud frame is through “flex anchors” these connectors are ¼” to 3/8” diameter stainless steel rods. Other anchors may also be used depending upon the specific application. The entire assembly weighs from 10 to 20 lbs per square foot.
Fig 1.1.1 GFRC
Fig 1.1.2 GFRC
fixing detail on concrete
keystone fixing details
Fig 1.1.3 GFRC
band
Fig 1.1.4 GFRC
cornice detail