40+ YEARS OF GRC
Like concrete, GRC is not a single material. Its basic ingredients are white or grey cement mixed with silica sand and alkali-resistant (AR) glass fibres plus, of course, water. Modern GRC also uses plasticisers and polymers. The AR fibres can either be in the form of chopped strands, from 6 to 25mm (2–4%) or as continuous filament for the spray process (5%) or filament winding (18–25%). It can be further reinforced, usually for local strengthening or additional safety or handling, with AR fabric or glass-fibre reinforced polymer reinforcement bars.
However, it is usually either made by the simultaneous spraying process or by premix casting. The Glassfibre Reinforced Concrete Association (GRCA) recognised early on that it would be necessary to establish quality standards for GRC.
To this end the GRCA introduced the Approved Manufacturers Scheme (AMS) as well as offering such publications as the Specification for the Manufacturing, Curing and Testing of GRC products and Methods of Testing Glassfibre Reinforced Concrete, and actively participated in the setting up of BS EN 1170 Parts 1–6 for GRC. Today, specifiers can request with confidence either Grades 8, 10 or 18 GRC made by a GRCA AMS member.
40 years to present
GRC rapidly established itself as an ideal material for architects who were looking for:
GRC provides the designer with a wider choice in form and texture than most other building materials. Back in 1977, this was recognised by Whinney Son and Austin Hall when one of GRC’s earliest prestigious buildings, 30 Cannon Street, was constructed in the centre of London. Some 1900 double-skin panels were made for this seven-storey building. The light weight of the hollow-section GRC panels enabled the architect to slope the walls outwards. The combination of this plus the slim nature of the panels meant that extra square metres of valuable central London office space were created. In 2012, it remains a landmark building whose pros and cons are still debated.
Around the world there have been many other iconic buildings clad in GRC over the past 40 years including, in 1984, 32-storey Parc Fifty Five building in San Francisco, which incorporated 3624 GRC panels including circular fluted columns and semi-circular arches with deep rustic joints.
In 1990, the first of more than 72,000 pieces of GRC, including 4000 finite shapes and ornate sculptures, were put in place on the historically important Shepard Hall building in New York.
The restoration involved the replacement of the original glazed terracotta and is only today nearing completion. Significantly, some of the units being put in place now are next to those installed 20 years ago with “the overall quality of match remaining very high” to quote architect Carl Stein, who added, “The material is appealing not only because of its great flexibility in form and surface but also because the very low maintenance requirements fit into our overall ‘green’ strategies.” Full details can be seen in the GRCA Shepard Hall video.
To the present day, GRC continues to be used on economically effective as well as prestige buildings around the world, with one unique example recently completed here in the UK. The University of Bradford’s School of Health used approximately 400 layout, component, and restraint drawings. Plus, the carefully controlled use of different doses of pigments for each panel produced an attractive patchwork of colours. The result is a striking, totally unique GRC façade which will prove to be of interest and inspiration to many for years to come. Nick Cooper of Architects Farrell & Clark says, “It is testament to the choice of material and manufacturer that the finished building replicates almost exactly the initial concept visualisation submitted for planning approval.”
Although cladding is the ‘pretty face’ of GRC, its combination of light weight, low maintenance and ease of moulding into complex shapes has resulted in a plethora of GRC products being manufactured around the world.
In civil engineering, GRC has been used for noise barriers, bridge deck and parapet formwork and tunnel linings. The use of GRC for housing components has also grown significantly.
Since its inception in 1969, GRC has continued to grow every year and continuously finds new applications where its unique blend of light weight and mouldability, durable surface and eco-friendly properties provides economic solutions to many problems.