Gulf Construction Online - The unique alternative

GRC

Around 23,000 sq m of terracotta has been replaced at Shepard Hall.

The unique alternative

The unique alternative Graham T Gilbert of Cem-FIL International provides some thoughts on architectural detailing in GRC.

01 March 2003

Glassfibre reinforced concrete (GRC) offers architects and engineers a unique opportunity as an alternative material for cladding new or existing buildings.

It is substantially lighter than precast concrete and is ideally suited as an original or complementary material. Complex, sculptured panels can be made more economically than precast and their reduced weight makes fixing and transport easier for these complex shapes.

However, since the finish on GRC can be identical to any structural or non-structural precast panels, they are frequently used in conjunction with the latter on the same building. GRC can also reproduce, in texture and colour, many natural stones.

First introduced more than 30 years ago, GRC is now established worldwide as a proven alternative building material with a blend of properties which help to create unique new or restored buildings.

Middle Eastern countries have, over the past 20 years, created a large number of architecturally individual buildings using GRC panels and decorative details. A fine example of this is The Clubhouse at Abu Dhabi. Designed by Diar Consult, the building is in the shape of a large falcon swooping onto a golf ball. The mouldability of GRC, which combined both shape and a dynamic mixture of colours and textures, helped to create this striking building. The panels were manufactured by Fibrex.

Meanwhile, although already 10 years old, the City Hall at Sharjah is another example of how GRC architectural elements can transform a building's appearance. Stone finished parapets, cladding, double-faced decorative screens as well as capitals and decorative arches helped to create this impressive building. Inside, GRC was also used for the stone-finish false ceilings. All elements were fabricated by Arabian Profile, Sharjah.

Nearly 20 years ago, the light weight of GRC panels, combined with their ability to be moulded into complex but durable shapes, was used to good effect by the architects Daniel, Mann, Johnson & Mendenhall on the 32-storey Parc Fifty Five building in San Francisco, US.

Originally constructed in 1984 as the Ramada Renaissance Hotel, it has survived the aggressive San Francisco urban environment for 19 years without a single refurbishment of the exterior and still looks as pristine as the day that it was erected.

A total of 3,624 GRC panels covered the entire surface area of more than 17,000 sq m. The buff-coloured GRC panels weigh only one-fifth of an equivalent precast concrete panel and so could be supported on a simple 125mm thick, cantilevered slab. Major savings in the structural steel and foundations were also made.

The panels themselves took full advantage of GRC's fabrication techniques, resulting is a variety of sculptured effects including fluted, circular and oval column covers; delicately combed, three dimensional spandrels; and large semi-circular arches with deep rustic joints.

Currently in New York, the architects Stein White Nelligan have specified Cem-FIL Star GRC for the restoration of Shepard Hall,the main campus building of New York City College. The reconstruction of the exterior of Shepard Hall is a multi-phase project which will eventually lead to the replacement of 72,000 units and more than 4,000 shapes, including many ornate sculptures.

In his approach to materials specification for the project, partner-in-charge Carl Stein rejected new glazed terracotta and cast stone because of their past poor performance in New York's polluted environment, preferring instead, after exhaustive testing to ASTM standards, the attractive properties of the metakaolin-modified form of Cem-FIL Star GRC.

The project has already replaced the upper 20 m of the main tower, clerestory window surrounds, coping and finials. A further 6,200 units were used to replace tracery and window surrounds for 12 stained glass windows 11 m high, 10 highly decorated finials 7 m high, and various copings, mouldings and quoins. Some 11,500 replacement units were also used to reconstruct a 35 m-tall tower, six projecting bay windows, each 11 m high by 6.7 m, numerous moulding surrounds, copings and quoins.

This project clearly shows that GRC has many properties that make it a particularly useful material since:
* It can replicate and replace a wide variety of materials.
* It can be moulded to accurately reproduce decorative and sculptural forms. Since GRC is dimensionally-stable during production, original examples can serve directly as models for the production moulds. Multiple copies can be readily fabricated.
* It is a thin shell product used to replace massive materials such as terracotta, precast concrete, natural stone or cast stone.
* Unlike many natural materials, GRC is widely available and supply is not limited by environmental constraints.
* It has excellent environmental resistance - the finished product will retain its architectural properties when subjected to freeze-thaw attack, ultraviolet exposure, abrasion from wind-borne grit and acid rain.

In Europe, the restoration of the prestigious Palace Hotel in Madrid, Spain, is another fine example of how GRC can be used to replace decaying stone-sculptured panels to their former glory.

The highly ornate exterior of the Palace Hotel in the centre of the city was spectacularly restored to its former glory with the moulded GRC parts being almost indistinguishable from the original carved stone in appearance and texture.