Makng a Concrete Gecko (7.5m )

I was commissioned to produce a concrete model of a gecko for a new housing development.

I am a sculptor,working in wood, steel , bronze , plastics and concrete.

For this project, I did quite a bit of research into high strength mortar mixes ( no stone , just sand / cement )

First , catch a gecko. This fellow helped out for a bit. Then I made a maquette...

Carved in foam and coated in acrylic plaster and finishing cloth ( fine chopped strand mat )

sketching with 10 mm steel rod

Using a ring roller, building the body, welding intersections

Heavier steel for strength and to bond to slab.

I glued hessian to the inside of each half of the steel work. This was to provide a surface that could accept an internal spray-up of polyurethane foam.The purpose of this was to provide a firm surface to apply the glass and steel fibre reinforced mortar on the outside , through the layers of bird mesh.

Chicken wire was stitched on to the steel rod armature. Cast concrete eyeballs fitted.

The mortar mix was designed in consultation with a concrete engineer from Tasmania.

3 parts sand

1part Portland cement

10% Magnesium Oxide ( high early strength )

Fly ash

steel fibre reinforcing

glass fibre reinforcing

water reducing compound ( the strength of concrete is inversely proportional to the amount of water added or water-cement (w/c) ratio.

I made 6 gum nuts in ferrocement also , to provide scale and to be used as casual seating.

Acid stain in various colours was worked into the surface and finally a coat of anti graf sealer that came from a firm called Gecko Coatings. It seemed appropriate...

Big test ! the gecko, weighing approx. one ton ( 1000kg ) was lifted out of the studio and trucked to its place in a playground. No cracking. The sub frame was anchored to the ground slab and a coating of rubber soft fall was put around .