Sprayed

The water and admixture (and polymer if used) are placed in a "high shear mixer" and the sand/cement are slowly added until a smooth creamy slurry is achieved. The consistency of the slurry can be checked using a simple slump test kit. Mixing time is about 1 - 2 minutes.

When ready the mix is transferred to a "pump/spray unit". The pump conveys the slurry at a regulated rate of flow to the spray gun. At the spray gun fibre, in the form of a roving, is chopped to a length of approximately 32mm and added to the slurry. The two materials are projected onto the mould surface using an air supply from a compressor.

The GRC material is sprayed and built up in thin layers until the required thickness is achieved - normally 10 - 15mm. Simple hand rollers are used to compact the material between layers.

The product is left in the mould and covered with polythene to prevent moisture loss until the next day. The product is then demoulded.

After demoulding the units are covered with polythene and allowed to cure for approximately 7 days. Alternatively, if a polymer curing compound is used in the mix the units can be exposed to the atmosphere immediately although it is advisable to keep them protected from direct sunlight or severe external conditions for a day or two. Reference should be made to the Polymer Supplier's instructions.