GFRC - Opai (Singapore) Pte Ltd

What is GFRC?

GFRC or Glass Fiber Reinforced Concrete is a specialized form of concrete. It’s a cement-based composite material reinforced with alkali-resistant glass fibers.

They perform the same function as reinforcing steel in reinforced concrete, adding flexural, tensile and enhanced strength. Thus, producing tough yet lightweight architectural concrete products such as building panels.

How does GFRC work?

The glass fibers used in GFRC contribute to the compound’s strength. The main tensile load carrying member is alkali-resistant fibers, while the polymer and concrete matrix bonds the fibers together and helps transfer loads from one fiber to another.

Without the fibers, the GFRC would be more prone to cracking and breakage. Finding the right mixture for concrete is a complex and confusing task, however, most mixtures have similar ingredients and proportions. Basic components in a good mixture include:

Fine sand
Cement
Polymer
Water

Alkali resistant glass fibres
Fiber content
Other admixtures

There are three different methods used in casting GFRC elements:

Spray-up

Spray-up GFRC is applied in a manner similar to shotcrete in that the fluid concrete mixture is sprayed into the forms. A customised spray gun is used to apply the fluid concrete mixture while also cutting and spraying long glass fibers from a continuous spool.

Spray-up produces exceptionally strong GFRC due to the high fiber load and long fiber length, although the equipment is costly.

Premix

Premix incorporates shorter fibers into the fluid concrete mixture, which is then poured or sprayed into moulds. Spray guns for premix do not require a fiber chopper, although they can be very expensive.

Premix also has less strength than spray-up since its fibers are shorter and distributed more widely throughout the mix.

Hybrid

The last method to create GFRC is to utilise a hybrid approach that applies the face coat using an affordable hopper gun and a handpacked or poured backer mix.

A thin face without fibers is sprayed into the moulds, and the backer mix is then packed in by hand or poured in similarly to ordinary concrete.

This is the approach used by the majority of concrete countertop manufacturers.