Tech Brief: Waterproof Shotcrete

SCP Tech Brief: Waterproof Shotcrete



Shotcrete is concrete or mortar that is pumped through a hose and sprayed at sufficient velocity onto a surface to allow it to stay in place with minimal rebound. Because the material must stick to slopes and vertical surfaces the consistency (slump) is usually dryer than conventional concrete. This dry slump and consolidation methods that typically only rely on the shotcrete application velocity itself can lead to a finished product that can be prone to desiccation and significant permeability. Many of the top shotcrete contractors utilize moist curing to offset some of these concerns. Moist curing can be difficult to maintain properly, along with sometimes being a source of labor, safety, and environmental issues.
SCP Colloidal Silica has shown to be an efficient and cost-effective alternative to moist curing for shotcrete. When spray-applied to the surface of the shotcrete, the colloidal silica penetrates into the accessible capillary pore space within the concrete. Once inside, it begins to react with available alkalis to form primarily calcium silicate hydrate (C-S-H), the same reaction product that cement and water produces that gives concrete most of its strength and durability properties. By filling the accessible pores, colloidal silica helps concrete retain the moisture that it needs to achieve optimal cure.
SCP products are the result of a proprietary application of colloidal silica technology. Over the course of the last ten years, SCP’s colloidal silica technology has proven to greatly reduce permeability of a variety of traditional concrete designs, including shotcrete. SCP products can be an important part of any shotcrete waterproofing solution.