Maryland Concrete Lifting
The Job
This Maryland concrete lifting project is located in Frederick, Maryland. The project is for the MARC system, on tracks also used by CSX.
The Challenge
MARC’s Brunswick Line includes a spur to Frederick, which utilizes a freight track that also serves multiple industrial sites, including quarries and concrete plants. As it winds through an industrial area towards the Frederick station, the line crosses multiple arterial roadways. As Frederick grows, traffic is increasing significantly with both cars and industrial truck traffic.
At two crossings, bellies have developed in the precast modular grade crossings. Water collects at the low spots, which then reduces bearing capacity of the base, causing deterioration of the adjacent asphalt pavement. This deterioration causes spalling of the panels, and ride quality problems for motorists.
The Solution
CJGeo’s rail grouting experience includes dozens of precast modular grade crossing stabilization projects. Working with the rail system’s on-call MOW contractor, a CJGeo polyurethane grouting crew grouted each of the two crossings in a day, each.
CJGeo uses CJGrout 48NHL, which is specifically formulated for high dynamic load applications. 48NHL provides multiple factors of safety from a compressive strength perspective, but is slightly elastomeric, which makes it much more durable than mudjacking or traditional cementitious pressure grouting grouts sometimes used to stabilize modular grade crossings on a temporary basis.
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New Jersey polyurethane grouting
The Job
This New Jersey polyurethane grouting project is located in Creskill, New Jersey. As part of a full gut renovation of the library, the architect specified lifting settled areas of the floor. The floor settlement was affecting approximately 3200 square feet, with settlement up to two inches.
The Challenge
The library building is a slab on grade, with relatively light design loads. The floor is approximately four inches thick, and reinforced with welded wire mesh. The original design to correct settlement was to use mud jacking. Mud jacking works well, but is rather slow, and tends to be very messy. Mud jacking uses cement-based grout pumped under high pressure below concrete to fill voids and push the concrete back up. A downside is that the grout is quite heavy, and the additional weight it adds to already compromised soils can cause additional future settlement.
The Solution
CJGeo proposed using CJGrout 28FDL geotechnical polyurethane grout as an alternative to the specified mud jacking process. CJGeo’s value engineer proposal was based on the following benefits of polyurethane grouting over traditional cementitious grouting:
- speed – polyurethane grouting tends to be significantly faster than cementitious grouting
- cleanliness – polyurethane grouting is a very clean process, including dustless drilling, mechanical connections to the slab, and material that scrapes off with a putty knife if it leaks from below a slab
- density – traditional mud jacking grout is approximately 50 times heavier than in place CJGrout 28FDL. This reduces the likelihood of future resettlement by minimizing the additional load that grout places on the underlying soils.
The architect and structural engineer accepted CJGeo’s value engineering proposal for this New Jersey polyurethane grouting repair. A crew of three CJGeo polyurethane grouting experts completed the repair in less than a day. Because polyurethane cures within a few minutes, the general contractor was able to move on to the next steps in the project very quickly.
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Bridge Approach Ground Improvement
The Job
This bridge approach ground improvement project by CJGeo is located in Richmond, Virginia. With multiple S curves and merges, I-195 in Richmond, Virginia is one of the most accident prone sections of interstate in Central Virginia. Significant settlement of multiple approach and departure slabs at various bridges didn’t make things any better. Improving the ride quality by addressing up to 6 inches of settlement was a critical part of a 2022 safety improvement plan.
The Challenge
Extensive settlement over the years had caused the pavement to become distressed. This was addressed over time with extensive patching of the pavement slabs. With no reasonable detour routes, shutting down traffic to facilitate repairs was not an option.
The Solution
While the original project designed required lifting all of the settled pavement, this would have been nearly impossible, given the extensive patching (including full depth filling of expansion joints with repair mortar).
CJGeo worked with the general contractor and VDOT to revise the repair plan to a combination of compaction grouting of the underlying soils, coupled with an asphalt overlay of the approach and departure slabs to restore the ride.
Polyurethane compaction grouting was performed to a depth of up to 25′ below the pavement surface. This was to consolidate poorly controlled backfill material, at two approaches (9 lanes total) and three departures (9 lanes total). Cutoff criteria was 0.05 inches of lift at each point/stage.
Milling and paving for a 30′ taper to provides a smooth transition and ride.
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Dollar Store Floor Void Filling
The Job
This floor void filling project is located about three hours west of Richmond, Virginia. A commercial contractor was performing a full gut renovation of a dollar store in a strip center. The building was approximately 30 years ago, and there were no signs of floor slab failure or settlement.
The Challenge
While cutting through the floor to install utilities, a 3″ void was discovered below the floor. Exploratory coring determined that voids ranged from 0.5 to 4″ throughout approximately 11,000 square feet of the space. The front of the building is at grade, but the rear of the building has an approximately 7′ tall CMU stem wall, which was backfilled with common borrow during original construction.
The Solution
The general contractor reached out to the structural engineer to notify them of the problem. The structural engineer then reached out to the geotechnical engineering, who recommended polyurethane grouting as the best way to fill voids below a floor. The geotechnical engineering is familiar with polyurethane grouting from working with CJGeo on similar repairs in the past. They know that polyurethane grouting:
- is very clean and fast, so is unlikely to slow progress
- is very lightweight, so is least likely of all grouts to cause additional settlement
- effectively cures instantly, allowing immediate resumption of activities in the area
CJGeo mobilized two geotechnical polyurethane grouting crews to the site and filled the voids over a period of two days. It took about 7,000 pounds of CJGrout 20SDB through approximately 500, 5/8″ holes to completely fill the voids. Cut-off criteria was cross-hole communication. The work was performed without disruption to the renovation activities.
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Fire Station Floor Lifting
The Job
This fire station floor lifting project is located about an hour east of Richmond, Virginia. The concrete slab on the grade floor inside of a fire station on the North Neck of Virginia settled up to two inches. As part of the investigation into the cause, an engineer discovered voids up to 8″ below the slab and multiple broken sanitary sewer pipes below the floor.
The affected areas needing slab foundation repair included a dayroom, kitchen & meeting hall.
The Challenge
In order to minimize disruption to the fire station’s operations, the proposed repair had to be quick, clean, and minimize uncertainty associated with the plumbing repair slab cuts.
The Solution
CJGeo performed ground improvement grouting of the underlying soils to 5′ below-grade utilizing plural component polyurethane compaction grouting, with CJGrout 35NHV. During the compaction grouting process (sometimes called structural polymer grouting), the CJGrout 35NHV lifted the floor back into place.
Because polyurethane grouts cure very quickly, the floor was repaired the day before the plumbing work was scheduled. This allowed the plumbers a stable work surface and eliminated the risk of stuck saws or sudden collapse of the floor during floor sawing for plumbing access.
Grouting sufficiency was verified by using pre & post-grouting DCP tests.
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Florida Grade Crossing Repair
THE JOB
Settlement and deflection of precast grade crossing were 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.
THE CHALLENGE
This Florida grade crossing repair had to quickly and thoroughly address the voids and settlement of the panels. Additionally, the material used for void filling and lifting needed to be resilient under dynamic loading from the train and vehicular traffic, and capable of performing well in saturated environments.
THE SOLUTION
High-density 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.
CJGeo modular grade crossing repair crew filled the voids and corrected settlement in fewer than four hours with CJGrout 48NHL. Milling and paving of the adjacent roadway were done the following day. The roadway and rail opened up immediately afterward.
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Railway Grade Crossing Repair
THE JOB
112 track feet of crossing panels settled, and needed grade crossing repair. 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 already been replaced twice. 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.
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.
THE CHALLENGE
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 the repair was designed around high service loads for heavy haul rail traffic.
THE SOLUTION
High-density polyurethane grouting using CJGrout 48NHL for this grade crossing repair. CJGrout 48NHL is designed specifically for rail and airfield grouting work.
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 took less than one day. The roadway and rail opened up immediately after the repair.
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Industrial Facility Floor Repair
THE JOB
The slab floor inside of a manufacturing facility in Hagerstown, Maryland settled. This caused equipment that was installed on the slab to become misaligned, requiring industrial facility floor repair.
A geotechnical investigation revealed voids below the slab due to the 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.
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.
THE 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, using CJGrout 20SDB. 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. A movement of 0.02 inches was used to determine the completeness of fill. This was confirmed by extensive extrusion of polyurethane through the adjacent saw cut control joints in the floor.
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Urban Grade Crossing
THE JOB
32 track feet of grade 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 a 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.
THE CHALLENGE
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 as a sand mine, so the settlement correction repair was designed around high service loads for heavy haul rail traffic.
Due to the scheduling constraints of the railroad, the repair method had to tolerate the potential for rail traffic during the repair.
THE SOLUTION
High-density polyurethane grouting to stabilize and lift the affected modular grade crossing panels, using CJGrout 48NHL.
Epoxy-augmented patching of the spalled areas to restore a smooth walkway for pedestrians.
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 took 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.
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Alley Settlement Correction
THE JOB
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, it could not be shut down. Due to the unpredictability of deliveries, the alley settlement correction work 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.
THE CHALLENGE
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. This reduces the likelihood of future consolidation of underlying soils.
Polyurethane grouting uses very 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. Hoses are lightweight, and easy to move out of the way if needed.
THE SOLUTION
A CJGeo polyurethane grouting crew spent two days performing this alley settlement correction project using CJGrout 30NHL. Multiple trash pickups and material deliveries happened during the grouting work.
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