A drop of the strong stuff

Today's designers are placing greater demands on building materials, as well as the suppliers of building materials.

Whether it's the architect or client, expectations are high. Not only do people want buildings with first class finishes at competitive prices; they want materials that are safe and easy to install, and which appear to have been made by craftsmen.

Is this a tall order? Not when it comes to a material that is used to mould a cornucopia of products from inspection chambers and manhole covers to cornices, copings and architectural precast concrete panels.

It is none other than the rather unglamorously named glassfibre reinforced concrete (GRC).

Do not be deceived by its prosaic name. A cementitious composite, GRC (originally developed as an alternative to asbestos cladding material) is a dead-ringer for natural stone or concrete - the darlings of today's designers.

As well as resembling more upmarket products, it boasts some formidable advantages. Not only can it can withstand the harshest environment, it is non-combustible, thinner than stone or concrete and only weighs up to a quarter of its more traditional counterparts.

Although introduced as long ago as 1969, GRC has taken more than 30 years to realise its full potential in the UK - a potential that is being enthusiastically bought to clients' attention by Nottingham-based Trent Concrete.

"I believe the potential for GRC is enormous," says Mike Downing, managing director of Trent Concrete. "I looked at it 30 years ago and didn't like it, but we bought GRC company Mouldform a few years ago and I have become totally converted."

What makes the product so different?

According to Richard Ferry, technical advisor and secretary of the International GRC Association, GRC can be seen as "a modern manifestation of the ancient art of using fibres' tensile strength to inhibit crack development and strengthen inorganic materials. Straw in clay or mud has been used for centuries to toughen the end product".

Historical comparisons

Ferry points to other historical comparisons such as wattle and daub along with horsehair in plaster.

"The use of all types of fibres within the concrete industry has been steadily growing over the last 30 years," says Ferry, "though only glass has generated a distinct industry based around its use. Steel fibres are generally too coarse and difficult to use in thin sections and polypropylene's elastic modulus is too low to provide effective reinforcement."

It is the combination of alkali resistant glassfibres and a cement-rich matrix that produces lightweight, easily formed thin sections that can be exploited in a wide range of architectural and civil engineering applications.

Since GRC's introduction, the product has matured and today's designer has, depending upon his performance requirements, a range of matrix modifiers such as acrylic polymers, rapid set cements and additives to improve the long-term stability of the material.

Other countries have not been so slow in realising GRC's potential, particularly when it comes to architectural cladding. Spain, Japan, the Middle East and the USA have been using the product for years. For example, Real Madrid's Santiago Bernabeu stadium is clad in GRC panels.

Having made a slow start, the pace of demand in the UK for GRC architectural panels is beginning to accelerate.

Trent demonstrated GRC's versatility on a contract in the West Midlands when the company completed an architectural GRC cladding contract at The Mailbox in Birmingham - a large mixed-use residential, retail, office, leisure and office development.

Because the front elevation of The Mailbox was partially clad in 600m2 of acid-etched reconstructed stone cladding, the architect was keen for this material to be echoed inside the building.

However, due to craneage difficulties, the decision was taken to substitute precast stone work with 1,400m2 of buff GRC cladding.

"As the site cranes did not have the radius to hang the heavy precast concrete panels within the development, GRC was used inside the building," says Downing.

Thanks to GRC's light weight and manoeuvrability, the panels were installed with no difficulties.

"If the weight advantage is taken into account at an early design stage, economies in foundation costs may be achieved," says Ferry. "Experience has also shown that erection of GRC panels takes up less crane time, and transportation costs are also obviously lower."

Switch from reconstructed stone cladding

Another project that switched from reconstructed stone cladding to GRC panels was Ocean Point at Leith in Edinburgh.

"GRC panels are being used to clad the shear walls in the building where the ability to use thinner panels is being taken advantage of," says Downing.

Is precast concrete in danger of being elbowed out of the market by this upstart? "We do not regard GRC as the competition," insists Downing. "We see it as complementary."

Proof of Trent Concrete's confidence in the material is to be found in the company's investment in two new facilities for its subsidiary, E&M Composities, which now provides the largest mould-building facility in the UK and whose headquarters are based at Sileby near Barrow-on-Soar.

GRC is also widely used for civil engineering uses such as sewer relining, permanent formwork, drainage channels and ducting.

"The first recorded use of GRC permanent formwork was the soffit decking of a bridge around 1970," says Ferry. "GRC is still commonly used in bridge construction, with for instance, many thousands of square metres used in the construction of the M25 and M60 orbital roads."

Other uses have been found for this product - namely in the manufacture of products as diverse as vanity units and bath surrounds.

With its ability to resemble natural stone, Downing points out that GRC gives designers an option that otherwise might have been denied them due to cost and difficulty of installation.

"The material is sprayed into very accurate, robust moulds to provide a high quality unit with a solidity comparable to dense natural stone materials," says Downing. "The finished units are lightly etched to produce a stone-like texture and the surfaces are then sealed after installation."

So what is GRC's life expectancy?

"Providing it's made and installed properly, it will stay more or less indefinitely," says Ferry. "After all, it's been around for 30 years already." n