Sprayed concrete – more commonly known as shotcrete – is a method of applying concrete or mortar projected from a nozzle at a high velocity on a vertical or sloping surface. The immense force of the impacting jet compacts the material in place, and can support itself without sagging – whether on a vertical, sloping or overhead surface.
The dry mix system is a popular choice where smaller volume and intermittent shotcrete is required – because it requires smaller and more compact equipment.
Gunite, a proprietary name for dry-sprayed mortar used in the early 1900's, has fallen into disuse in favour of the modern ‘shotcrete’.
The wet mix system is ideal for high production applications, where access allows the application equipment and delivery trucks to operate on a continuous basis.
Shotcrete technology has seen many developments over the years, but amorphous silica and steel fibres are by far the most significant and have made the largest impact.
In shotcrete, reinforcement provides ductility to a brittle material. Steel and Macro fibre reinforced shotcrete have gained world-wide acceptance as a replacement for traditional wire mesh reinforced plain shotcrete.
Rock support is only called upon to carry significant loads once the rock surrounding an underground excavation deforms. This means that unevenly distributed, non-elastic deformations may overload and lead to failure of the support system – unless that system has sufficient ductility to accommodate these deformations.
Microsilica SF is an extremely fine pozzolan – a cementitious material that reacts with the calcium hydroxide produced during hydration. While rebounding material is an inevitable byproduct of shotcrete’s high velocity, Microsilica SF helps to reduce it. It’s other benefits also include:
Our recommendation: add Microsilica SF in quantities of 8% by weight of cement to achieve significantly higher compressive strengths than the value of plain shotcrete mixes. The end product will be an extremely strong, impermeable shotcrete.
Add Microsilica in quantities of 8% by weight of cement to achieve significantly higher compressive strengths than the value of plain shotcrete mixes. The end product will be an extremely strong, impermeable shotcrete.