In situations where the cracks and fissures or the soils are too small to allow the slurry grout to infiltrate these spaces, pressure grouting with microfine cement can be used to permeate the cracks and fissures in the soil.
The process produces a solidified mass to support increased loads and fill voids in the ground. Permeation grouting is used to control water seepage, provide temporary and permanent underpinning of existing foundations, improve the bearing capacity of soils under existing foundations, and excavation shoring.
Chemical grouting, a form of permeation grouting, utilizes chemical substances for improving soil structure and water control. This grouting method is also used to repair fractures in concrete and rock. The most common are sodium silicate, acrylate, lignin, urethane, and resin grouts Shroff and Shah, Sodium Silicate System: Sodium silicate grouts are most popular grouts because of their safety and environmental compatibility.
It has been developed into various grout system such as silicate chloride amide system, among others.
Most of the systems are based on the reacting a silicate solution to form a colloid which polymerizes further to form a gel that binds the soil particles. The silicate solution concentration that may be used in grouting is in range of 10 to 70 percent by volume, depending on the material being grouted and the desired result to achieve. For a system of using amide as reactant, the amide concentration may vary from less than 1 to greater than 20 percent by volume. In practice, the amide concentration ranges between 2 to 10 percent US Army Corps of Engineers, The initial minimum viscosity of a grout that can produce a gel has a SiO2:Na2O ratio of 3.
The rate of reaction and strength of gel are directly proportional to the concentration of silicate and catalysts in the grout at constant temperature respectively Shroff and Shah, Sodium silicate is noncorrosive to metals.
Reactants such as amide and their water solutions will attack copper and brass, but they are noncorrosive to aluminates and stainless steel. The chloride solutions are not corrosive to iron and steel in the sense that acids are; however, if steel in a chloride solution is exposed to air, rusting will occur at the junction of the liquid and air.
Silicate Chloride Amide System: The silicate chloride amide system is one of the widely use silicate grout system containing sodium silicate as a gel forming material. The silicate aluminates-amide system has been used for strength improvement and water cut-off. Its behaviour is similar to the silicate-chloride-amide system but is better for shutting off seepage or flow of water. The cost is slightly higher, and this system can be used in acidic soils.
Amide will act as a reactant and the calcium chloride, sodium aluminates will be used as the accelerator. These reagents bring an almost instant setting time and produce very low penetrability type gel that are unsuitable for permeation treatments Rawlings, The function of the accelerator is to control gel time and impart strength to the gel.
Excessive amounts of accelerators may result in undesirable flocculation or formation of local hardening. This causes variations in both the gel and setting times that would tend to plug injection equipment or restrict penetration, resulting in poorly grouted area. Therefore, a retarder should be added in the mixture for delaying the setting time and formation of gelation US Army Corps of Engineers, Table 1 shows different rheology parameters of silicate grout in different concentration.
Comparison of Chemical Grout Properties: Over the last 30 years, a few hundred different compounds of chemical grout are available. However, the origin of chemical grout still remains a few types such as silicates, acrylamide, epoxy, and some fatty acid derivates. Generally, chemical grouts are intended to penetrate and fill narrow joints or soils with very small pore size. Basically, the comparison will made according to the penetrability of grout in soil and the range of curing time for each type of grout Magill and Berry, Acrylamide: Acrylamide based grouts come closest to satisfying the attributes of an ideal grout.
They show easy penetration and maintain their initial viscosity until at the very end of the gelling stage when they rapidly set. They have good gel time control and adequate strength for most applications Karol, The grout exhibits good penetrability, with a constant low viscosity during induction period and better gel control with adequate strength. However, it is highly toxic and unsuitable for potable water application Shroff and Shah, Acrylamide has a low chemical resistance toward acidity condition; therefore, it is not suitable for application in peat because peat is acidic in nature.
The new acrylate gels are suitable for works that require low viscosity and a well controlled gel time, however, the cost is higher than sodium silicates Nonveiller, So it is better than acrylamide grout. However, NMA has an extremely low viscosity with about 1 to 2 cP. The viscosity is similar to that of water; therefore the pumping flow rate will be same as the water. It has low stability under constant head pressure of the groundwater and is especially bad where acidic conditions and organic contaminants are present.
The gel time is affected by the temperature and catalyst concentration. Acrylate grout is rarely used in geotechnical field since the gel will swell considerably in the presence of water.
As a result, strength of the grout will further reduce since existence of water will dilute the concentration of grout Magill and Berry, Polyurethane: Polyurethane chemical grout is composed of two components of water activated material called hydrophobic and hydrophilic resin.
However, many of other type resin are produce base on these two resins. The viscosity of grout is very high with is range from to cPs. The limitation is that the pH of water will affect the reactivity of grout. A higher pH value with more than pH 7 will increase the activity of grout. Thus, it is favorable for the alkaline soil and unsuitable for the acidity soil like peat. Besides, the gel time of the polyurethane is controlled by the molecular weight, intermolecular forces, and stiffness of chain units, crystallization and cross linking Vinson, The polyurethane is toxicity in nature, so, it mostly applicable in forming to block water inflow water reactive resins.
Epoxy Resins: Epoxy resins are liquid pre-polymers with hardening agent, they usually exhibit very high tensile, compressive and bond strength. Generally epoxy resins will have either good chemical resistance or good heat resistance Magill and Berry, The low viscosity has a better penetrability but greater shrinkage and less strength due to the weak bonding lead to more subsidence, whereas the high viscosity may better if adequate pressure is maintained long enough to permit the grout filling into small void Erickson, However, the epoxy is one of the resins types which are toxicity nature and a special care during the handling Rawlings, Aminoplasts: Aminoplasts consist of urea and formaldehyde.
The rapid grout reaction in hot and acidic environments makes this product difficult to handle. Chemical grouting is a means of blocking the intrusion of groundwater in pipelines or underground structures.
Soil stabilization with compaction grouting is a form of grouting technology carried by PrimeLine Products. It displaces and reinforces loose and fine soils; stabilizes sinkholes and underground voids; and improves the load-bearing characteristics of soil under structures.
In addition to trenchless and pipeline equipment, PrimeLine Products carries a line of cementitious products and chemical grouts to stabilize soil, grout annular spaces, and carry out slab jacking. These products include:. Depending on the accelerator amount, this product expands with water and cures quickly as a corrosion and microorganism-resistant foam, suitable as a below-grade barrier to water and chemicals. It has a low viscosity and is not flammable.
Aqua-Tite — A fast-reacting polyurethane foam for blocking high-volume water flows. It has a formulated density of four pounds per cubic foot and a stable pour temperature between 70 and degrees Fahrenheit.
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