Sprayed concrete is a dense, small-aggregate concrete pneumatically projected at high velocity against a surface. The force of the impact compacts the concrete to such an extent that for most applications the material has zero slump. As a result, sprayed concrete significantly outperforms traditional concrete in terms of both strength and durability.
A mixture of cement and aggregate is combined with a measured amount of water, sufficient to hydrate the mix. Where necessary, admixtures and metal fibres may be added to the sprayed concrete material in repair situations where high levels of abrasion would cause conventional concrete to break down prematurely. The strength of sprayed concrete will depend on application specifics, but is generally applied in a range between 30 Mpa and 50 Mpa; adequate for all but the most complex and challenging of maintenance projects. In normal applications, sprayed concrete is based on ordinary portland cement, which is able to withstand the rigours of most industrial repairs. For situations where heat, corrosion, impact and rapid repairs are a prime consideration, calcium aluminate cement is preferred, for both longevity and effectiveness.
These benefits contribute in no small way to making sprayed concrete a superior maintenance solution. In repair and maintenance situations, the performance of sprayed concrete includes:
- High density
- High, early and ultimate strength
- Low water/cement ratio
- Excellent adhesion and bond strength
- Low permeability
- High abrasion resistance
- Cold climate resistance
- Resistance to aggressive environments
- Ability to create any shape or applied to any surface