Graham Gilbert, chairman of the Glassfibre Reinforced Cement Association, explains how medical science and defence technology played an important role in building a 12-storey-high statue of the Merlion, Singapore's national icon
A 37m version of the Merlion, the mythical creature with a lion's head and fish's body that symbolises the legendary origins and maritime history of Singapore, now greets visitors to the Sentosa Island theme park. The sculpture is the latest and largest in a series of big structures which have become a speciality of South Australia-based Glenn Industries.
Preliminary studies demonstrated that glass-reinforced concrete was the most suitable material for the structure because of its watertightness, workability and ability to produce a monolithic appearance. Extensive research was undertaken by Glenn Industries, with particular focus on the possible problems of structural resonance due to the slenderness of the figure's body and the significant mass of the head.
Glenn Industries employed Australian artist James Martin to create a 1.2m-high model from which they could establish precise surface co-ordinates for the enlarged structure and so produce structural drawings incorporating the Merlion's shape, form and expression.
This was done as the result of an unusual three-way partnership between Glenn Industries, the Adelaide Children's Hospital Cranio-Facial Unit and the Australian Department of Science and Technology. Using the hospital's X-ray tomography and 3D digitising technology, an exacting computer image of the model was created. This was scanned using defence technology from the Department of Science and Technology to provide precise measurements and co-ordinates. With this data, Glenn Industries was then able to devise a construction method using x and y co-ordinates which could be referenced to standard building techniques and surveys.
Using these co-ordinates, a steel armature was built to provide the structural frame for the Merlion. This was then covered with expanded metal lath developed for use with grc. The sprayed grc matrix composition formed a dovetailing/clinging effect to the pre-tensioned lath. This allowed spraying of vertical and inverted areas such as the Merlion's scales, mane and the underside of the jaw leading to the chest area.
The matrix used to construct the structural skin was manufactured as a dry-mix mixed with a polymer compound for enhanced adhesion, ductility, waterproofness and curing. This was sprayed in a raindrop pattern encapsulating accurately-metered alkali-resistant glass fibre to a thickness of 10-12mm and then compacted with serrated rollers; the layer was sprayed until a 20-25mm structural skin was built.
To this grc base a polymer structural coat was then applied to a thickness of 20-60mm, depending on the amount of relief required by the sculptor. The coat was designed to provide extended working time and was coloured with blended oxides. In addition, special masonry stains were used to penetrate without surface build-up and give the Merlion the colours and hues of a real lion. The entire inside of the sculpture was sprayed with a proprietary cement to conceal and provide corrosion protection to the steel armature.
An important technical consideration was the night-lighting of the sculpture. Spotlights would have distorted its appearance. The solution was provided by Adelaide artist Clifford Firth's fibre-optic tubes, 16,000 of which are built into the structure to provide the required lighting effect.
Since its completion last June, the Merlion sculpture has attracted thousands of visitors. It is a dramatic example of the enormous potential of grc as a composite structural material with unrivalled facility for detail.