Bridge Approach Grouting
The Job
This bridge approach grouting project is located near Lexington, Virginia. It is on Interstate 81, which has some of the highest truck traffic in Virginia. The Virginia Department of Transportation maintains this section of Interstate 81.
The Challenge
Settlement over time caused voids under three lanes of approach slab at an overpass structure. During precipitation events, the voids became saturated, and then act as diaphragm pumps. The high dynamic loads from the heavy truck traffic effectively pump the fines out of the saturated base materail.
Over time, this resulted in extensive deterioration of the adjacent asphalt pavement, along with distress of the concrete approach slabs.
The Solution
Working with the local bridge maintenance group and their on-call maintenance contractor, CJGeo proposed a polyurethane bridge approach grouting program to restore stability to the slabs. Previous repair attempts had used flowable fill to attempt to fill the voids below the pavement. This generally doesn’t work very well, and proved to not be suitable in this case, either.
Primarily constrained by maintenance of traffic concerns, CJGeo undersealed all three lanes of the approach over two nights. Grouting was done using CJGrout 40NHL, which is optimized for heavy loads, wet environments, and is capable of lifting settled pavements.
Because 40NHL cures to 95% within a few minutes, by the time the injection holes are patched, treated slabs and soils are ready for traffic as usual.
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Virginia Polyurethane Grouting
The Job
This Virginia polyurethane grouting project is located in Blacksburg, Virginia, at Virginia Tech. The work was done to support continued occupancy of the structure, after voids as deep as two feet were located below the floor slab.
The Challenge
A small area of the ground floor slab on grade settled, primarily adjacent to the basement, which is only under about 20% of the building footprint. The basement contains mechanical equipment, and ties to a large crawlspace used as a ventilation duct.
Upon initial discovery, the university’s on-call geotechnical and building envelope consultant performed exploratory drilling to determine the extent of voids. Several auger bores for exploration of the backfill material identified poor control during installation as the most probable cause of settlement.
The Solution
CJGeo was the most responsive bidder on the owner’s solicitation, which called for filling the voids below the floor with CJGrout 20SDB geotechnical polyurethane. 20SDB is specifically formulated for maximum expansion, high mobility, and very low exotherm.
One particular challenge was the amount of glass gravity drain piping below the floor. Because much of the building is lab space, when it was built, the most chemical-tolerant pipe available was glass. So, it was very important that the polyurethane grouting work not damage the relatively fragile pipes.
CJGeo timed its work around spring break to avoid any disruption to classes, research, and offices. The work took six days onsite, and a total of just under 10,000 pounds of CJGrout 20SDB.
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Apartment Floor Lifting
The Job
This apartment floor lifting project is on a military facility in Washington, DC. During turnover of a unit, the property management company discovered signs of significant settlement affecting the interior floor. There was a significant crack showing through vinyl flooring, and up to 1.5 inch gaps below the baseboard in a carpeted room.
The Challenge
The primary challenge for the general contractor on this project was repairing the floor as quickly as possible. The unit was only going to be unoccupied for about two weeks between tenants. The contractor not only had to repaint, install all new floors, but also had to address this settlement.
The Solution
The general contractor reached out to CJGeo to assess the feasibility of raising the floor using polyurethane grouting. Having worked together in the past, the general contractor knew that CJGeo’s polyurethane grouting process is significantly faster than traditional mud jacking or concrete replacement.
A single CJGeo polyurethane grouting crew took less than a day to complete this apartment floor lifting repair. The total area grouted was around 750 square feet. Using CJGrout 28FDL, the grouting process corrected all of the settlement. Because polyurethane grouts are about 95% lighter than traditional grout and backfill materials, the likelihood of the grout material inducing future settlement is virtually eliminated.
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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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