Sodium silicate grouting is a mineral grouting (as opposed to chemical grouting) process primarily used for water control below grade. These grouts are very low viscosity (below 30 centipoise). Reaction profiles are site adjustable by varying reactant dosing. Sodium silicate grout does not expand. Sodium silicate grout is primarily water. Therefore, this type of grout is best for use in damp or wet environments, though syneresis is relatively limited in soils even above the groundwater table.
Sodium silicate is higher viscosity than colloidal silica, but because of how it interacts with the soil, is able to increase the strength of treated soils.
Composition
The following components make up sodium silicate grouts:
- resin
- water
- reactant, typical dibasic ester
The ratio of resin to water and reactant controls the consistency of the finished product.
Placement
Sodium silicate grouts can be pumped separately and mixed at the placement point continuously, or batched and then pumped as a single stream. Pumping method is generally means & methods and varies depends on site conditions, geology, and a host of other factors.
Sodium silicate grouts do not expand, and are slightly more viscous than water. Their relatively low viscosity allows them to be pumped quickly, without fracturing the treatment zone. This type of grout will not permeate clays or silts, but is excellent for sands with minimal fines content.
TAM tubing (Tube-a-Manchette) is the most common method for installation sodium silicate grout. Using TAM tubing allows for precise application of grout at up to 10 different injection points at once. TAM tubing is typically installed using sonic drilling. Sonic drilling is very precise and capable of drilling through about whatever debris or obstacles are in the treated soils.
Typical Sodium Silicate Grouting Repairs
Sodium silicate grouts are excellent for permeation grouting of soils, binding them together, and significantly reducing their permeability. Unlike soils treated with single component polyurethane resins, soils grouted are generally easily hand excavatable, but depending on soil type, can gain significant strength. Compared to acrylic grouts, which are similar viscosity, soils treated with silicate grout are generally more friable, but similar reductions in permeability, and significantly stronger.
Sodium silicate grouts are generally chosen because of their low viscosity and ability to increase the strength of sands. Viscosities similar to water allow mineral grouts to penetrate very tight cracks, and also to follow very fine water flow channels. Uniform permeation is the key to thoroughly addressing water flows through soils.
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