Constructions for the subsoil
Accelerating agent for concrete and consolidation
Waterglass is broadly used in the construction of tunnels as an accelerating agent for concrete. After digging, proceed by coating the internal walls of the tunnel using the shotcrete technique (sprayed concrete). The silicate mixed directly in the concrete spray nozzle immediately fixes the concrete, allowing the application of multiple concrete layers of considerable thickness.
Before digging tunnels, it is sometimes necessary to consolidate the soil. In the most straight forward cases, one proceeds with cement grout, but if there are problems due to the presence of very small gaps or the presence of a water table, “chemical” injection is necessary.
The injected products are made with waterglass and help achieve consolidation of the soil and impermeability to water, through the formation of silica gel which reinforces and seals the ground. The method for obtaining a gel varies; one technique is the Toosten process which uses separate injections of waterglass in solution, followed by a reagent such as calcium chloride, which instantly turns into a gel by reaction. Alternatively it is possible to control the gel time by adding a slow reagent, which is pre-mixed into the silicate and then injected.
Some co-reagents are sodium carbonate, sodium aluminate or organic esters. The high degree of flexibility of the silicate formula is clearly a significant benefit during the application stage.