Acrylic grouts are exceptionally low viscosity (below 10 centipoise), whose reaction profiles can be controlled onsite, and which do not expand. Acrylic grouts are hydrophilic. Cured acrylic grout is up to 75% water. Therefore, acrylic grouting is best suited for use in damp or wet environments.
There are two general classes of acrylic grouts; acrylamide, and acrylate. CJGeo primarily performs acrylic grouting with acrylate.
Composition
The following components make up acrylic grouts:
- resin
- water
- salts, to control set time
The ratio of resin to water controls the consistency of the finished product. There are also different polymer contents depending on manufacturer and product. Generally, higher polymer contents yield stiffer cured grout consistencies.
Straight resin pumped 1:1 with water will yield a stiff gummy bear/silicone consistency finished product. Resin cut 1:1 with water and then pumped 1:1 with water will yield a cooked egg white consistency finished product. Non-cohesive soils treated with acrylate grout are friable, non-permeable, and will typically stand on their own, but still be hand-excavatable.
Placement
Acrylic grouts are pumped separately up to the injection point. Similarly to our CJGrout geotechnical polyurethanes. A mixing head designed to ensure through mixing between the two sides then mechanically hooks to injection tubing or ports to place the material.
Acrylic grouts do not expand, and are barely more viscous than water. Their low viscosity allows them to be pumped relatively quickly, without fracturing the treatment zone.
CJGeo uses PLC-controlled pneumatic pumps and splitters to place acrylic grout at up to 10 individual points simultaneously. Knowledge during grouting is critical; the equipment logs and reports pressures and volumes per injection stage. This facilitates CJGeo providing detailed logs, and evaluating the response of soils to the grouting process.
Most acrylic grouting is done via the Tube-a-Manchette method, commonly called “manchette” or “TAM” grouting. TAM pipes are PVC pipes with grout holes protected by rubber sleeves every 1.25 feet. Drill casing is installed using sonic drilling, the TAM pipes are dropped down the casing, then the casing is retracted. This leaves the TAM pipe in the ground, where it’s then grouted around using a benonite & cement mix. After this annular grout sets, a straddle packer is dropped down the TAM, aligned with a particular stage, inflated, then grouted through. After a stage is grouted, the straddle packer is moved up or down to the next grout stage.
Typical Acrylic Grouting Repairs
Acrylic grouts are excellent for permeating fine grained soils, binding them together, and significantly reducing their permeability. Unlike soils treated with single component polyurethane resins, soils grouted with acrylics are generally easily hand excavatable.
Acrylic grouts are generally chosen because of their very low viscosity. Viscosities similar to water allow acrylics to penetrate very tight cracks, and also to follow very fine water flow channels. Acrylate’s exceptionally low viscosity also allows it to permeate soils very uniformly, unlike resins, which tend to fracture soils, resulting in non-uniform permeation.
Alternatives to Acrylic Grouts
Colloidal silica and sodium silicate are two common alternatives to acrylic grout. Both are mineral grouts, so do not generate heat as they cure. Colloidal silica is lower viscosity than most acrylates, and similar in price. However, colloidal silica results in friable soils, whereas soils treated with acrylate will elongate in tension.
Sodium silicate is less expensive, but higher viscosity than acrylics. Therefore, sodium silicate is better for courser grained soils. Soils treated with sodium silicate will have higher compressive strengths than can be achieved with acrylic or colloidal silica grouts.
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Facing a challenge that may be addressable with acrylic grouting? Give us a shout or shoot us a text. Click the state marker for the location of the project for contact info for the appropriate rep.
