Glass Reinforced Concrete (GRC)

About Glass Reinforced Concrete (GRC)

Glassfibre Reinforced Cement ( GRC ) is a composite material consisting of a mortar of cement and fine aggregate reinforced with alkali resistant glassfibre. The GRC may contain additional filler materials, pozzolanic materials and admixtures. The fibre contents are typically 3% to 5% by weight defending on product application and production method employed. The properties of GRC depend on a wide range of variables. These include the method of manufacturing, mix formulation, fibre product type, length and orientation, add mixtures used etc. A GRC material may therefore be tailored to meet the particular requirements of a specific application.


Typical Formulations

Ingredients Spray Premix
Cement 50 kg 50 kg
Silica Sand 50 kg 50 kg
AR Glass fiber 4.5-5% 3-4%
Superplastisizers 0.5 kg 0.5 kg
Polymer 5 kg 5 kg
Water 13.5 L 14.5 L

Quality cement is ‘Ordinary Portland Cement’. White Portland Cement is used for any architectural buildings, and interior and exterior decorations. The construction which demands the higher and quicker initial strength prefers 53-grade white cement. As compared to 33 and 43 grade white cement 53-grade has a quicker and stronger setting. 53 mega Pascal strengths can be attained within 28 days of setting. The cement is used in RCC and pre-stressed concrete of higher grades, cement grouts, and instant plugging mortars. 53-grade cement has stronger adhesive bonding than the other 33 and 43-grade ones. It has a higher compressive strength. The volume of cement is more for same weight, which results in more opacity and the fineness of the cement. A mixture of limestone and other raw materials like argillaceous, calcareous, and gypsum is prepared and then grinded to prepare OPC (Ordinary Portland Cement).

Alkali Resistant Glass fiber for used in cement based System AR fibers are made by the continuous filament process. Molten glass is fed through a platinum (bushing ) which contain very large numbers of small holes ( tips ). The molten glass is pulling through bushing as a continuous fiber. It is passes through the fine water mist and is then pass over roller that applies an organic processing: The fibers are then wound on to a former to make a cake. This cake is then put through a time / temperature regime to cure the size. The cake are then either wound together to form a roving ( or cheese ) or put through a chopping unit to cut the fiber to required length ( Chopped / strand ) The selection of the type and amount of size used apex the end fiber product in term of stiffness, resistance to abrasion and can have other effect. The diameter is uniform with little variation. The alkali resistance is confirmed by the composition of glass itself and not on a protective coating.

Superplasticizers (SPs), also known as high range water reducers, are additives used in making high strength concrete. Plasticizers are chemical compounds that enable the production of concrete with approximately 15% less water content. Superplasticizers allow reduction in water content by 30% or more.

Silica sand, also known as quartz sand, white sand, or industrial sand, is made up of two main elements: silica and oxygen. Specifically, silica sand is made up of silicon dioxide (SiO2). The most common form of SiO2 is quartz – a chemically inert and relatively hard mineral

Typical Strength Properties of GRC

Property After 28 days After Ages
Density, dry (kg m3) 1800-2000 1800-2000
Impact strength, charpy (Nmm/mm2) 8-15 4-5
Compressive strength, edgewise (MPa) 40-60 50-60
Yield, TY (MPa) 5-8 7-10
Ultimate strength, FU (MPa) 10-14 10-14
Modulus of elasticity (MPa) 10 x 103 - 20 x 103 18 x 103 - 22 x 103
Direct Tension:
Yield, TY (MPa) 4-6 4.5-7
Ultimate strength, TU (MPa) 4-7 4.5-8
Strain to failure (%) 0.1-0.2 0.03-0.06
Interlaminar not available not available
In-plane (MPa) 4-7 4-7
Coefficient of thermal expansion(x 10 ⁶/°C) 10-18 10-18 10-18
Thermal conductivity(W/m.°C) 0.5-1.0 0.5-1.0 0.5-1.0

GRC Forms

  • All
  • Window Surrounds
  • Cornices
  • Brackets
  • Columns
  • Capital and Base
  • Dome
  • Screen and Panel
  • Baluster Railings
  • Arch
  • Landscapings

GRC Benefits

Light Weight

GRC can be cast in thinner sections and is therefore as much as 75% lighter than similar pieces cast with traditional concrete


GRC can have flexural strength as high as 4000 psi and it has a very high strength-to-weight ratio.

Corrosion Resistance

GRC Composit products provide longterm resistance to severe chemical and temperature environments.

Design Flexibility

Sprayed or poured into a mold, GRC can adapt to nearly any complex shape, from rocks to fine ornamental details.


GRC will outlast precast concrete, cast stone, even some natural stone. Durability has been increased through the use of low alkaline cements and pozzolans.


Often materials used in or for construction can be expensive. But, with GRC, you get great value for money.

Design Criteria

GRC Design Criteria

An understanding of basic molding and casting constraints of glass fiber reinforced concrete will provide a better understanding for the architect and engineer of how GRC design shapes and forms are to be manufactured. Here are some designs considerations that may affect the cost of GFRC used in your project. GFRC can reproduce intricate details or smooth sweeping curves. Details and undercuts require rubber mold liners. Simple smooth flats and curves can be cast in rigid molds of fiberglass. While rubber molds are slightly more expensive, the cost may be minimal if the casting is repeated several times. Numerous casts of a GFRC shape are more economical per piece, than onetime-only casts. GFRC can be cast in pieces up to 12’ in length. Maximum area 60-80 Sq. Ft & depends on design & thickness. However, the longer the length, the more difficult it is to handle and ship the GFRC casting. We recommend a maximum area 60 to 80 Sq. Ft depends on design & thickness for most moldings. If longer lengths are required, pieces can be field joined.

Quality Assurance

GRC Quality Assurance

The success of any GFRC system depends on a coordinated effort by the designer, manufacturer and installer. Sequence, deliveries and manufacturing tolerances are critical to the success of the project and should be mutually agreed upon by all parties. Submittals and shop drawings should be utilized extensively to familiarize the designer and installer with the method of attachment, reinforcement and fabrication. This process alerts the designer to any possible conflicts. The GFRC shop drawings should be complete in every detail to allow the installing contractor a complete inventory of parts and pieces, as well as expected tolerances.


A properly designed, manufactured and installed GRC system will provide an innovative and visually pleasing appearance, while often reducing overall cost, onsite labor requirements and shortening construction schedules. Glass fiber reinforced concrete (GRC) offers an endless variety of decorative and ornamental shapes and forms at affordable prices. Permeability of GFRC depends on the mix design and compaction and is better than most cementitious materials.