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Concrete Lifting Projects

By applying unique solutions to increase the safety and longevity of our environment.

Florida Grade Crossing Repair

Crossing

Heavy haul freight, mainline highway

Problem:

Settlement and deflection of precast grade crossing was causing highway pavements to deteriorate.  The crossing is owned and maintained by the large business park it serves, is used by CSX, and crosses a major highway maintained by FDOT.  Exploratory geotechnical investigations determined that the soil under the crossing had sufficient bearing capacity.  However, a void had developed under the crossing, which allowed water to pool under the slabs.  The slabs deflected under vehicle & rail traffic, which pumped the sandy backfill material out from under the slabs.  

The adjacent asphalt had failed, which channeled water into the void below the panels, causing the problem to worsen.

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Constraints:

This Florida grade crossing repair had to quickly and thoroughly address the voids and settlement of the panels.  Additionally, the material use for void filling and lifting needed to be resilient under dynamic loading from train and vehicular traffic, and capable of performing well in saturated environments.  

Solution:

High density polyurethane polyurethane grouting to stabilize and lift the affected precast grade crossing panels.  Polyurethane grouting is far superior to mudjacking, because it allows for rail traffic during the repair, and immediate resumption of road traffic.  Because the adjacent asphalt had significantly deteriorated, the immediate return to service allowed full size paving equipment to traverse the crossing immediately after the polyurethane grouting was done.

Result:

CJGeo modular grade crossing repair crew filled the voids and corrected settlement in fewer than four hours.  Milling and paving of the adjacent roadway was done the following day.  The roadway and rail opened up immediately afterwards.

Vineland, NJ Grade Crossing

Railway Grade Crossing Repair–Vineland, New Jersey

Crossing Use:

Heavy haul freight (silica mine), rural highway by short line

Problem:

112 track feet of crossing panels settled. This caused the adjacent asphalt pavement to fail. The crossing ran diagonally across the highway. The road was graded so that the crossing was the primary flow path for surface water. The crossing had been replaced twice in the past. The last replacement used flowable fill as the base material. The crossing panels experienced approximately 1 inch of deflection with highway traffic. There were also 4 inch voids below the panels.

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Lifting modular grade crossing using polyurethane grouting.

With highway traffic from heavily-loaded vehicles, the crossing deflected enough to squirt water three to four feet in the air. This water pumping action actively pumped the subbase material from under the crossing.

Constraints:

The repair had to allow immediate vehicular traffic to facilitate a single lane closure that was flipped halfway through the repair. The repair also had to allow for immediate resumption of rail traffic. The crossing served a sand mine, so repair was designed around high service loads for heavy haul rail traffic.

Solution:

High density polyurethane polyurethane grouting to stabilize and lift the affected modular grade crossing panels.  

Supplemental anchor bolting was also used to ensure longterm integrity of the repair.

Result:

CJGeo modular grade crossing repair crew filled the voids and corrected settlement in less than a day.  Asphalt patching was done concurrently with polyurethane injection.  The entire repair was completed in less than one day.  The roadway and rail opened up immediately after the repair.

Industrial Facility Floor Repair

The Job:

The slab floor inside of a manufacturing facility in Hagerstown, Maryland settled. This caused equipment which was installed on the slab to become misaligned, requiring industrial facility floor repair.

A geotechnical investigation revealed voids below the slab due to settlement of the underlying soil. The affected area was built over approximately 10 feet of fill during construction. Engineering analysis showed that the soil was likely poorly compacted, but had consolidated with time.

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Polyurethane grouting

The Challenge

Due to the sensitive electronic equipment within the work area, the repair had to be very clean and dust free. Though analysis determined that the underlying soils had most likely completed consolidating, the owner’s geotechnical consultant recommended limiting additional weight placed on the fill material.

The repair area was also more than 100 feet from the nearest exterior access. The floor had started to settle before the equipment was installed. It was very important that the slab not be lifted during the void filling process.

CJGeo’s Solution:

Geotechnical polyurethane grouting to fill the voids below the slab floor.  Polyurethane grouting is superior to mudjacking in situations like this because it is considerably cleaner, much faster, and allows for immediate reuse.  

The material used in polyurethane grouting is much lower weight than mudjacking grout.  This reduces the weight applied to the underlying soil.  Lower weight materials reduce the chance of resettlement.

A single CJGeo polyurethane grouting crew completed the industrial facility floor repair in less than a day.  Due to the extreme sensitivity of the equipment to lifting, a specially-formulated plural component polyurethane grout was selected for undersealing without lifting.  

Precision equipment was used to monitor the floor during undersealing.  Movement of 0.02 inches was used to determine completeness of fill.  This was confirmed by extensive extrusion of polyurethane through the adjacent saw cut control joints in the floor.

Urban Grade Crossing, Cumberland, NJ

Urban modular grade crossing repair–Cumberland, New Jersey

Crossing Use:

Heavy haul freight (silica mine), urban main road by short line

Problem:

32 track feet of crossing panels settled. This caused the adjacent asphalt pavement to fail, and caused tripping hazards at the adjacent pedestrian sidewalk. The grading in the area was relatively good, however the adjacent ballast was fouled, which caused water to accumulate under the crossing panels and wash out the sandy subbase material. The crossing had been replaced recently. Due to the urban, primarily passenger automobile traffic, there was little deflection of the crossing panels from highway traffic. However, there were up to four inches of deflection from rail traffic loading.

The deflection from rail traffic loading caused the top edges of adjacent panels to be in compression with each other. This caused extensive spalling of the surface, which affected two of the panels. While not a functional problem for panel integrity, the spalled areas were within the sidewalk portion of the crossings, and therefore posed tripping hazards.

Constraints:

The repair had to allow immediate vehicular traffic to facilitate a single lane closure. The repair also had to allow for immediate resumption of rail traffic. The crossing served a sand mine, so repair was designed around high service loads for heavy haul rail traffic.

Due to scheduling constraints of the railroad, the repair method had to tolerate the potential for rail traffic during the repair.

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Polyurethane grouting, asphalt patching and panel patching.

Solution:

High density polyurethane polyurethane grouting to stabilize and lift the affected modular grade crossing panels.

Supplemental anchor bolting was also used to ensure longterm integrity of the repair.

Epoxy-augmented patching of the spalled areas to restore a smooth walkway for pedestrians.

Result:

CJGeo modular grade crossing repair crew filled the voids and corrected settlement in less than a day.  Asphalt patching was done concurrently with polyurethane injection.  The entire repair was completed in less than two hours. The roadway and rail opened up immediately after the repair.  Traffic control was done to accommodate pedestrians and roadway traffic.

Two trains passed through the crossing over the panels being repaired during the repair. This did not affect the integrity of the repair.

Alley Settlement Correction

Challenge:

Dewatering associated with a basement excavation caused settlement of an adjacent alley’s pavement. The alley pavement consisted of 4″ concrete base, 2″ course of asphalt, and 3″ thick pavers. The alley served as the sole service and parking entrance to an adjacent residential tower, so could not be shut down. Due to the unpredictability of deliveries, the repair also had to allow for intermittent traffic during work.

The pavement had settled up to 3 inches, with nearly 3,000 square feet affected. In addition to being adjacent to two 50+ feet deep basements, one end of the work area was bound by the Navy Yard metro station.

Solution:

While the customer was familiar with, and inquired about cementitious pressure grouting, CJGeo proposed polyurethane grouting. Polyurethane grouting allows for immediate traffic after repairs, and also for intermittent traffic during repairs. With in-place unit weights of around 4 PCF, polyurethane grouts are significantly lighter than cementitious grouts, which reduces the propensity of future consolidation of underlying soils.

Polyurethane grouting is done using compact equipment, as well. Instead of large pumps, mixing equipment and hard to maneuver hoses, polyurethane grouting is all down out of a box truck, with lightweight, small hoses that are easy to move out of the way if needed.

Result:

A CJGeo polyurethane grouting crew spent two days raising the alley. Sawing was done prior to lifting in order to facilitate differential movement between the settled slabs & the adjacent paved areas. Multiple trash pickups and material deliveries were made to the adjacent property during the grouting work, without disruption to either party.

Grain Bin Floor Repair in MD

Challenge:

The floor of a 105′ diameter grain bin settled. The floor had a bin sweep installed, that was mounted on the top of the unloading tunnel, which ran down the center of the structure. Where the slab floor butted up to the tunnel walls, the floor had settled 2″ on one half, and 3.5″ on the other half. This caused issues with operating the bin sweep, because it was designed for a smooth, level floor.

The owner’s alternative was to remove the entire floor and pour a new floor. This would have been incredibly expensive, and take a very long time. The only access into the bin was two 2′ wide by 4′ tall doors, located 5′ above exterior finish grade, and 2′ above the bin floor elevation.

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Limits:

Due to the nature of the commodity business, mobilization and completion of the grain bin floor repair had to be fast. Additionally, the repair had to return the floor to its original profile, along with the turned down ventilation trenches in the floor. The extensive turned down ventilation troughs made this floor very susceptible to cracking. The floor was 6″ thick, but then went to 24″ thick at the ventilation troughs. Slabs with non-uniform thickness require extreme care and attention to avoid differential lifting.

The design loads for the floor are approximately 3500psf, so the material used for lifting the floor had to be relatively high strength.

The Solution:

CJGeo proposed polyurethane grouting for filling the voids below the floor and lifting it back into place.  The minimum bearing capacity of the proposed materials was 5500PSF, ensuring adequate bearing capacity even under full load.

Result:

CJGeo mobilized two polyurethane grouting crews to the site. The work was completed over a period of two days, during which more than 7,000 pounds of polyurethane grout were installed using three reactors running simultaneously. Multiple reactors (pumps) helped to ensure thorough lifting of the slab and the ventilation troughs. The crews that completed this job have collectively performed millions of pounds of polyurethane grouting, ensuring successful completion of this grain bin floor repair job.

Blower Slab Stabilization

Challenge:

During a routine inspection, extensive voids were discovered under the slab supporting a ventilation blower at a wastewater treatment plant.  Staff were concerned that the lack of support under the slab would cause it to settle.  As visible in the pictures, this would easily cause extensive damage to this critical equipment.

Constraints:

The repair had to address the voids under the entire area of the slab, including the areas where the slab surface was unaccessible.

The Solution:

CJGeo proposed polyurethane grouting for filling the voids below the blower slab.  The minimum bearing capacity of the proposed materials was 3700PSF, ensuring adequate bearing capacity and long term stability.

Result:

A CJGeo polyurethane grouting crew filled the voids below the blower base and adjacent sidewalk in less than two hours.  Operations were not affected; the equipment stayed in service during the entire repair. 

Warehouse Floor With Embedded Rail

Challenge:

25,000 square feet of industrial floor at a military facility settled up to 4 inches and was affected by sub-slab voids.  The affected area also included 250 track feet of embedded rail, which was set in an independent, thickened slab section.  The building had been used for warehousing, but was being transitioned to light manufacturing/maintenance.  

Plans called for an 4” thick overlay slab being installed, with a vapor barrier, over the existing floor.  Geotechnical investigation work determined there were extensive voids below the floor throughout the area affected by settlement. 

Limits:

The proposed repair method had to provide adequate bearing capacity for manufacturing, and ensure complete void filling and stabilization.

The Solution:

Polyurethane grouting to fill voids under the floor to stabilize against future settlement.  Additionally, in areas which had settled, polyurethane grouting was proposed for correcting settlement.  

Due to extensive compressive soil layers below the floor, polyurethane grouting was proposed as an alternative to the specified cementitious grout.  The specified grout had an in-place density exceeding 115 pounds per cubic foot.  The proposed polyurethane grout had a constrained density of 5.5PCF, yet a bearing capacity exceeding 12KSF.

Result:

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CJGeo mobilized three polyurethane grouting crews to the facility, with a combined pumping capacity exceeding 5,000 pounds per hour.  Nearly 2,000 dime-size injection holes were drilled through the slab, and 5,000 cubic feet of polyurethane grout was installed under the floor & section of embedded rail.  Void filling was confirmed by visual inspection (material showing at adjacent drilled holes to injection locations), and slab lift. 

In areas which had not settled, 1/8 inches of lift was used as the benchmark change in elevation to confirm complete void filling.  Areas which had settled, including the embedded rail sections, were lifted up to 3 inches above the original elevations.

Runway Slabjacking

Challenge:

The hinge slab of a runway at an overpass settled.  This caused up to a 1.5″ difference in elevation across the joint between slabs.  The slabs had previously been repaired with pressure grouting.  The previous runway slabjacking was done using a cement-based grout.   The previous slabjacking required drilling 3″ holes on 4′ centers over the entire area.  They had to be core drilled due through the 26″ deep slab.

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Limits:

The proposed repair had to work despite previous repair attempts with cement grout.  The repair had to be completed in fewer than 48 hours, with the ability for air traffic at any time during the repair with as few as 10 minutes’ notice.  The settled slab was nearly twice as thick as the adjacent slab, which was 14″ thick.

The Solution:

CJGeo proposed polyurethane grouting to raise the settled slabs.  Polyurethane grouting allows for immediate resumption of traffic, and is much more efficient to install than cement-based grout.

Because the previous repair had left hundreds of 3″ core holes through the slab, polyurethane grouting was idea due to its 5/8″ hole diameter.   CJGeo proposed a 6 pound foam for this project, which was originally specified for cement-based grout. 6 pound foam provides adequate bearing capacity and has excellent lifting capacity.

Polyurethane grouting can also be performed in the rain without affecting the material. Due to the extremely short runway shutdown period, speed of execution despite any bad weather was critical.

Result:

CJGeo mobilized three polyurethane grouting rigs to the site.  The joint was saw cut full depth using a 48″ walk-behind saw prior to lifting. Lifting was done using up to four polyurethane reactors running simultaneously. Drilling was completed using a combination of pneumatic rock drills & electric hammer drills.

The runway slabjacking project was completed in less than the allotted time. CJGeo subcontracted to TST for this project. The project also include restriping and asphalt pavement restoration on the runway shoulders.

Boston 9″ Floor Lift

The floating slab floor of a flex space building in Boston, Massachusetts settled up to 9 inches.  The tenant was approaching renewal, and had mentioned that the floor settlement was affecting the usability of their space.  To avoid losing his long term tenant, 

Limits:

The tenant was an environmental testing company for ships entering the Port of Boston.  Daytime staffing levels were high, but there were also continuous nighttime operations to service incoming cargo shipments.  The tenant made it clear to the building owner that operations could not be affected at all by any floor repairs.

The Solution:

CJGeo proposed polyurethane grouting using plural component TerraThane to fill voids below the floor and then raise it back to flat.  The floor slab settlement resulted from backfill consolidation after building pad preparation.  The finished floor elevation was roughly 5′ above the adjacent parking lot, which was at original grade.  

Since polyurethane grout is significantly lighter than cement based grouts (4lb/cuft vs 130lb/cuft), using polyurethane grout helps reduce chances of resettlement from applying additional burden on top of the backfill material.

Polyurethane grouting is also exceptionally clean; injection holes are just 5/8″ diameter, dustless drilling is used, and the process is very quiet.  This facilitates work in occupied facilities with minimal disruption.  All raw material is contained in CJGeo’s trucks, with no concrete truck deliveries, which also allows for easy scheduling of night work or other special schedules around tenant needs.

Result:

CJGeo mobilized a two pump polyurethane grouting truck to the site. The first shift was daytime work, and corrected the worst areas of settlement in the warehouse area.  The following night, the second and final shift of work was done to correct settlement in the office areas which were unoccupied at night.

The repair was successfully completed with no disruption to the tenant, and the slab was restored to level.

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