Structural Polymer Grouting

CJGrout Geotechnical Polyurethanes

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CJGeo performs structural polymer grouting using plural component polyurethane grouts and prepolymer chemical grouts. Plural component polyurethane grouts are rigid, hydrophobic grouts which are not susceptible to dimensional instability due to changes in environmental moisture levels. CJGeo performs permeation grouting of soils using prepolymer chemical grouts, which can be hydrophobic or hydrophilic, depending on desired characteristics of the treated soil mass.

Structural polymer grouts are great for filling voids immediately adjacent to structures. This includes voids below pavement, footings or other walls.  Ground improvement works by injecting polymer directly into soils.  Grouting with polymers in this fashion can be designed to perform similarly to permeation grouting or compaction grouting, depending on the polymer selected.

Types of Structural Polymers

Plural component polymers and prepolymers are the two types of structural polymer grouts.

Plural component polyurethanes are classified by ASTM  as rigid cellular plastics. They are generated onsite by processing through two part systems at a 1:1 by weight mix ratio.  Specialized equipment pumps & places plural component polyurethanes. It is typically contained in self-sufficient box trucks.  Expansion of plural component polyurethanes starts within a few seconds of injection. Depending on the application, set times range from less than 10 seconds to nearly five minutes.  Typical physical characteristics are densities between 2lb/cuft and 8lb/cuft, and associated bearing capacities of 3.5ksf to 23ksf, respectively.  

There are two broad categories of single component prepolymers. Hydrophilic, and hydrophobic, and usually referred to as chemical grouts.  Hydrophilic prepolymers react with and entrain moisture. Hydrophilics are well suited for saturated environments.  If the environment dries, the grout dries as well and can shrink.  Hydrophobic prepolymers react with, but do not entrain moisture. Therefore, dry environments usually call for hydrophobic grouts.  Environmental moisture levels do not impact dimensional stability of hydrophobic polyurethanes.  One advantage of hydrophilic polyurethanes is their ability to stretch and deform more than most hydrophobics.

Polymer Grouting Applications

Structural polymers can correct a number of geotechnical, structural and nuisance/use problems.

Geotechnical applications for structural polymer grouting include:

  • permeation and compaction grouting to improve the bearing capacity of soils,
  • controlling ground water movement through soils,  
  • Bulk void filling to address geologic and utility-caused sinkholes

Both plural component and prepolymer grouts are appropriate for geotechnical applications. Plural component grouts generally most appropriate for compaction grouting and bulk void filling applications. Prepolymer and acrylic grouts for permeation grouting of soils.

Structural applications for polymer grouts include:

  • correcting settlement of building elements such as slab on grade floors, and
  • stabilizing soil below, and lifting, spread footings and other load bearing elements.  

Plural component polyurethanes are most commonly used for settlement correction.  Applications include lifting highly loaded pavements, such as railroad grade crossings, to lifting footings which have settled.

Nuisance and Use applications of polymers typically involve:

  • stopping water intrusion into structures,
  • correcting non-critical settlements such as tripping hazards in non-structural concrete slabs,
  • and correcting slight movement of slabs caused by slab curl,

These often have effectively no impact on the integrity of a structure. However, they can pose significant operational hazards for material handlers in distribution centers.

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Structural Polymer Grouting Project Profiles