Structural polymer grouting to fill a sinkhole under mainline railroad after jack & bore lost face under tracks.
CJGeo perform 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 grouting can be used to fill voids immediately adjacent to structures, such as voids below pavement, footings or other walls. It can also be used to improve soils 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
There are two broad types of polymer grouts used for structural polymer grouting: plural component polyurethanes and prepolymers.
Plural component polyurethanes are classified by ASTM as rigid cellular plastics; and are generated onsite by processing through two part systems at a 1:1 by weight mix ratio. Specialized equipment is required to transport, pump & place plural component polyurethanes, and is typically contained in self-sufficient box trucks. Expansion of plural component polyurethanes starts within a few seconds of injection, and 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.
Single component prepolymers are typically broken down into two broad categories; hydrophilic and hydrophobic, and usually referred to as chemical grouts. Hydrophilic prepolymers react with and entrain moisture, so are well suited for environments which are continuously saturated. If the environment dries, the grout dries as well and can shrink. Hydrophobic prepolymers react with, but do not entrain moisture, so are well suited for both continuously saturated and also dry environments. Environmental moisture levels do not impact dimensional stability of hydrophobic polyurethanes. An advantage of hydrophilic polyurethanes is their ability to stretch and deform, which is advantageous in dynamic environments so long as they’re continuously wet.
Polymer Grouting Applications
Structural polymers may be used to 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 to controlling ground water movement.
Chemical grouting with structural polymer to address water intrusion and slab curl in produce processing facility.
through soils. Bulk void filling to address geologic and utility-caused sinkholes is widely performed using polymer grouts. Both plural component and prepolymer grouts may be used in geotechnical applications; plural component grouts generally being used for compaction grouting and bulk void filling applications, and prepolymer grouts for permeation grouting of soils.
Structural applications for polymer grouts include correcting settlement of building elements such as slab on grade floors, and even 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 typical revolve around stopping water intrusion into structures and correcting non-critical settlements such as tripping hazards in non-structural concrete slabs, and correcting slight movement of slabs caused by slab curl, which have effectively no impact on the integrity of a structure but pose significant operational hazards for material handlers in distribution centers.
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Kirk Roberts | (757) 592-0452