Shotcrete is pneumatically applied low slump concrete that is blown onto the receiving surface with compressed air. Shotcrete has a relatively low water/cement ratio, high cement content, and typically small aggregate not exceeding pea gravel size. High compressive strengths in excess of 5,000 psi are commonly attained. The sticky nature of shotcrete allows it to be placed on vertical and even overhead surfaces without the need for formwork. With proper quality control, a wall surface can be built out to an 8 inch thickness or more in a single pass.
Schnabel typically uses shotcrete to build temporary and permanent facings for our soil nail retention walls, but it can also be used as a facing for any other type of earth retaining wall. For soil nail walls, a temporary shotcrete layer of 4 to 6 inches is applied directly to the excavated ground surface, often prior to soil nail installation. If the wall is to be permanent an additional 6 to 12 inches of reinforced shotcrete will be applied after the soil nails are installed. The surface of the permanent facing can have a finish that varies from gun finished, to finish troweled, similar to a formed concrete wall, to sculpted and stained.