Jet grouting is an erosion based grouting method that mixes cementitious grout with soil at high pressure. Jet grouting is economical at scale, but with relatively high mobilization costs, a generally messy operation, and large equipment, several jet grouting alternatives can work better, particularly on smaller sites or in sensitive locations.
The Basics of Jet Grouting
Jet grouting pumps very high mobility cementitious grout into the soil at high pressure. Typically, a rotating head ensures uniform mixing of the grout material and existing soils. The process generates spoils. Spoils volume is typically the volume of material displaced by the grout, minus material consumption by voids.
Jet grouting equipment is typically quite large. Track-mounted drills, grout pumps, and spoils handling equipment all have a relatively large footprint.
Jet Grouting Alternatives
Permeation grouting is the most common alternative to erosion-based grouting methods. It uses lower pressure & placement rates, but generally achieves the same end result of binding treated soils to reduce permeability and increase strength. Permeation grouting relies on the permeability of treated soils, so is less appropriate for clays and impermeable soils.
Permeation grouting with acrylic grouts is an excellent alternative to jet grouting, particularly on sensitive, tight sites. At shallow depths, permeation grouting typically uses sacrificial tubing installed from the surface. When performed at depth, Tube-a-Manchette (TAM) grouting uses special casing and packers to precisely deliver grout to targeted treatment areas.
Acrylic Grouting
Acrylic grouts are exceptionally low viscosity–they can be difficult to distinguish from water. Because of this, acrylic grouts are know for their ability to very uniformly permeate fine grained soils, such as silty sands and silty clays. Similar to prepolymers, acrylic grout set times are easily controllable by varying the catalyst dosage.
In place, acrylic grouts range from the consistency of a cooked egg white to a hard silicone rubber. Cured acrylic grout is highly elastic. Above the water table, outside of temporary support, acrylics are usually not the best choice.
Advantages of Permeation Grouting
Permeation grouting is an excellent alternative to deep foundation repairs in the case of unconsolidated granular soils below concrete slabs and foundations. In case of settlement, chemical grouting soil stabilization is generally paired with a shallow foundation repair such as polyurethane grouting. Compared to deep foundation repairs, chemical grout soil stabilization is:
Cleaner
Permeation grouting equipment is compact & electrically-powered. Dustless drilling is easily accomplished for interior applications. Mechanical connections in all components of the injection equipment ensure no loose material. At depth with TAM tubing, the drilling process for TAM tubing installation is significantly less disruptive than the jet grouting process.
Less Disruptive
Compared to erosion based grouting, permeation grouting is phenomenally less disruptive. Jet grouting is an incredibly equipment & mess-intensive process. For open sites, that’s often not a problem. For work adjacent to water, occupied structures, or other sensitive applications, jet grouting is usually best avoided unless it’s the only way to achieve project requirements.
Faster
Permeation grouting is generally faster than underpinning repairs or other deep grout injection processes due to its compact equipment and ease of installation. Because of its compact equipment, fast reaction times and minimal surface disruption, work can easily be scheduled and planned to accommodate an area’s or structure’s normal use.
Other Permeation Grouts
Alternative permeation grout materials include sodium silicate and microfine cement. Microfine cement can be more economical at scale, but is not as clean as resin or acrylic grout. Sodium silicate is exceptionally effective in sands, and similar in price to acrylic grouting. Neither is dependent on moisture exposure for long term dimensional stability.
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