Richmond 195 Slide

Settlement Correction

Millions of pounds and counting.

polyurethane featured

CJGeo got its start in 2008 as Concrete Jack, a residential mudjacking company. Since then, more than our name has changed. CJGeo has grouted for settlement correction on more than 5,000,000 square feet of structures and infrastructure ranging from office and data center floors to runways and interstates.

Void Filling

Most settlement is accompanied by voids. Whether immediately below a slab or structure, or within the underlying or adjacent soils, the first step to settlement correction is void filling.

For voids greater than a few inches deep, a high mobility void filling grout, like CJGrout 20SDB, is usually most appropriate. CJGrout 20SDB can fill voids up to a feet feet deep in a single pass. Because it weights less than 3lb/cuft, is highly unlikely to cause additional settlement. 20SDB is exceptionally mobile, so can also be used for undersealing very small voids associated with slab curl.

For slabs with higher loads, or in wet environments, a higher density geotechnical polyurethane, such as CJGrout 35NHV, may be most appropriate.

If voids are just a few inches, and lifting is required, the lifting grout is usually used for void filling at the same time as lifting.

Concrete Lifting

Once voids are filled, the expansion of the polyurethane grout can be used to raise the slab or structure. There are two ways to lift slabs or structures with geotechnical polyurethane. Either shallow injection immediately below the structure, or injection into the underlying soils. Shallow injection works the same as mudjacking, and is most appropriate when the cause of settlement has resolved. Soil injection works the same as compaction grouting, and is detailed below, and is used when the underlying soils still have the potential to consolidate.

These criteria are used to determine the most appropriate CJGrout system for a particular application:

  • amount of differential settlement (differential settlement requires lower mobility)
  • size of the slab (smaller slabs require lower mobility)
  • slab thickness & loads (higher loads require denser grout)
  • presence of standing water (some grouts are better for water displacement)

The concrete lifting process is relatively straightforward. The expansion of the geotechnical polyurethane injected below the slab or structure displaces it upwards. Movement is slow and precise. Elevation measuring is generally done using rotary lasers, and is measured in hundredths of an inch.

Ground Improvement

If settlement is ongoing and due to consolidation or deterioration of the underlying soils, injecting grout into the soil is the most appropriate repair. Some typical applications of compaction grouting using geotechnical polyurethane include:

  • grouting poorly controlled fills in bridge approach & departures
  • reducing the permeability and densifying WOH organic soils
  • correcting global settlement

CJGrout 40NHL is the most common geotechnical polyurethane grout used for compaction grouting.

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