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

Stormwater Sinkhole Repair

The Job

This stormwater sinkhole repair project is located at a data center near Dulles, Virginia. Within a few months of construction, a depression started over a utility intersection within a street intersection inside the fence. Time showed that asphalt patching wasn’t going to solve the problem, so a geotechnical engineering firm was brought into investigate the sinkhole.

The Challenge

The first step taken was video inspection of all the gravity utilities in the area. None of them were showing any signs of leaks of water or soil. Utilities within the zone of influence of the sinkhole include:

  • stormwater (deepest & largest)
  • fire protection
  • two fiber duct banks
  • three electrical duct banks

Given the shear number and crossing alignments of utilities, and lack of leaks, the presumption was that backfill consolidation over the underlying stormwater structure was the most likely cause of the settlement.

The Solution

Due to the presumed cause of inadequate compaction, the geotechnical engineer recommended polyurethane compaction grouting to the owner. Compaction grouting with polyurethane grout is significantly faster, less disruptive, and less likely to displace adjacent structures than cementitious compaction grouting.

CJGeo proposed using CJGrout 20SDB for this stormwater sinkhole repair project. 20SDB is well suited for filling bulk voids, and has very little expansive pressure, so minimizes the chances of fouling or damaging the adjacent critical utilities.

A CJGeo polyurethane grouting crew was able to complete the repairs over two days onsite.

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Maryland compaction grouting

The Job

This Maryland compaction grouting project is located on East West Highway, in Chevy Chase. A few years after finishing construction of a new mixed use building with underground parking, the public sidewalks began to settle.

The Challenge

A local consulting geotechnical engineer was the first call by the building owner. After reviewing the construction drawings, and visiting the site, the geotech recommended performing a few hand augers. The hand augers were to:

  • confirm the sidewalk construction matched the plans
  • check for bulk voids below the sidewalk
  • confirm the backfill material
  • see just how loose the backfill material was.

The hand augers confirmed that the sidewalk was indeed pavers over asphalt, over a thin concrete mud slab. There were sporadic voids below the mud slab, up to six inches deep. The backfill material was poorly controlled soil, and was relatively loose.

The Solution

Due to the backfill material being relatively loose, and the building being new enough that the soils hadn’t consolidated on their own, the geotechnical engineer recommended polyurethane compaction grouting to the owner. Compaction grouting with polyurethane grout is significantly faster, less disruptive, and less likely to displace adjacent structures than cementitious compaction grouting.

CJGeo proposed using CJGrout 20SDB for this Maryland compaction grouting project. 20SDB is well suited for filling bulk voids, and has very little expansive pressure, so minimizes the chances of fouling or damaging drainage board.

A CJGeo polyurethane grouting crew was able to complete the repairs over two days onsite.

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Facing a similar challenge to this Maryland compaction grouting project? Give us a shout or shoot us a text. Click the state marker for the location of your project for contact info for the appropriate rep.

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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Facing a similar challenge? Give us a shout or shoot us a text. Click the state marker for the location of your project for contact info for the appropriate rep.

New Jersey Lightweight Fill

The Job

This New Jersey lightweight fill project is located in Secaucus, New Jersey. It’s part of a two building, wood framed multifamily structure over a concrete podium. The site is located very close to the Hudson River, so the underlying soils are poor, and there is a high likelihood of future flooding. As a result, the ground was improved using rammed aggregate piers, but then needed to be brought up approximately 2′ above existing grade.

The Challenge

Rammed aggregate piers were only able to improve the site soils so much. To avoid the costs of rigid inclusions or piles, the design team had to reduce the load applied by the backfill needed to elevate the site. The maximum unit weight was 30lb/cuft, and because of potential flooding, the material had to be permeable, in order to reduce uplift potential.

The Solution

CJGeo proposed using 25lb/cuft CJFill-High Permeability to backfill the stem walls, to bring the building pad up approximately two feet. 25lb/cuft CJFill-HP is provides excellent bearing capacity, but is hand excavatable.

Hand excavatability was important on this project. There was extensive under slab plumbing required, and the lightweight fill couldn’t impede on its installation. A great advantage of 25lb/cuft CJFill-HP is that it provides a clean, stable working surface that easily supports mini and mid-size excavators.

CJGeo mobilized a wet batch cellular concrete plant crew to the site. The crew used silt fence to break the roughly 80 thousand square foot pour into roughly 150CY placements. Each individual pour on this New Jersey lightweight fill project allowed the plumbing contractor to drive their mini excavators on it the following day. The plumbers enjoyed the clean, dry working surface.

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Facing a similar challenge? Give us a shout or shoot us a text. Click the state marker for the location of your project for contact info for the appropriate rep.

North Carolina Compaction Grouting

The Job

This North Carolina compaction grouting project is located at a military facility in eastern North Carolina. To facilitate the renovation of an adjacent office building, the owner installed eight mobile office buildings. Before the mobile offices were put into use, they settled up to three inches. As a result, the owner had to stabilize the structures before moving any equipment and people into the structure.

The Challenge

The site comprises of sand backfill over native loose sands. The eight mobile buildings bear on masonry piers resting on plastic load distribution pads. The piers and pads are on approximately 6′ centers, spread uniformly throughout the structure. The crawlspace is too shallow to safely enter.

The Solution

CJGeo proposed using CJGrout 35NHV to perform compaction grouting below the piers to stabilize the loose soils. 35NHV is a 3.5lb/cuft rigid polyurethane foam. It performs well for void filling and compaction grouting in wet environments.

Special polyurethane grouting rigs generate CJGrout 35NHV onsite. The rigs have hoses up to 400 feet long, which convey the material from the grouting rigs to the placement area. For this project the 35NHV was injected using sacrificial tubing. The tubing passes through holes in the floor through the crawlspace, to roughly 3′ below the pads.

One of CJGeo’s polyurethane grouting crews was onsite for three days to complete this North Carolina compaction grouting project. CJGeo used rotary lasers to monitor the floor elevation over each pier during grouting. The cutoff criteria was movement of approximately 0.25 inches. Then, a carpentry crew jacked and shimmed the beams after the grouting. Finally, a flooring crew restored the flooring afterwards.

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Facing a similar challenge? Give us a shout or shoot us a text. Click the state marker for the location of your project for contact info for the appropriate rep.

Coke Gas Pipe Fill

The Job

This coke gas pipe fill project is located in Middletown, Ohio, at Cleveland Cliff’s Middletown Works facility. Middletown Works determined that the coke plant would be more costly to repair than to replace, so elected to demolish the plant.

The Challenge

A demolition contractor working to dismantle parts of the onsite coking plant had to remove approximately 350LF of coke gas pipe. The work area is located in the basement of the coking plant.

Coke gas residuals will spontaneously combust when exposed to the air, but the pipe had to be cut into roughly 3′ pieces to remove it. The pipe fill grout had to:

  • completely fill the pipe
  • coat the residuals to minimize air exposure
  • cut easily
  • add as little weight as possible to the pipe sections

The Solution

CJGeo proposed using CJGrout-20SDB to fill the pipes. 20SDB is a 2lb/cuft rigid polyurethane foam, specifically formulated to flow long distances before setting.

CJGrout 20SDB is generated onsite by special polyurethane grouting rigs. The rigs have hoses up to 400 feet long, which convey the material from the grouting rigs to the placement area. For this coke gas pipe fill project, the crew had to run hoses approximately 250 feet into the building, down multiple stair cases. The hoses are lightweight and about 2 inches in diameter, so this isn’t a problem.

One of CJGeo’s polyurethane grouting crews was onsite for two days to complete the project. Once the coke gas pipes were filled, the demolition contractor cut them into 3 foot long pieces with traditional band saws bagged the sections, and removed them from site.

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Facing a similar challenge? Give us a shout or shoot us a text. Click the state marker for the location of your project for contact info for the appropriate rep.

Pit Fill With Lightweight Flowable Fill

The Job

An abandoned water treatment plant at a federal facility was being rehabilitated and brought back into service. As part of the project, lightweight flowable fill was needed to fill a 12′ deep tank below the building floor needed to be filled before installing a new floor and equipment.

The Challenge

The majority of the pit is below ground water level. The original foundation design used a 62PCF fill density for the pits, presuming they would only ever hold water.

The backfill material also needed to completely encase a number of new micropiles installed for machine bases.

The designer had two competing interests–given the closeness of the water table to finish floor, avoid any buoyancy of the fill material, while using the lightest possible material to avoid inducing any settlement.

The Solution

CJGeo proposed filling the pit with CJFill-UW, at 70lbs/cuft. At 70lb/cuft, there are no uplift concerns, and the material is just barely denser than water, which helps minimize the amount of anticipated settlement. To help ensure future excavatability, CJGeo used a sanded base slurry (as opposed to the usual neat mix slurry) to generate 830CY of lightweight flowable fill material. The 28 day design strength was 150psi. The average 28 day tested compressive strength was 200psi. The removability modulus of the material is 0.75, which means the material is readily excavatable.

Traditional “lightweight” flowable fill is closer to 95lb/cuft. At 150psi, 95lb/cuft material has a removability modulus of 1.18. This is above ACI’s benchmark value of 1 for ease of excavatability.

For this project the CJFill-UW was generated by adding preformed foam to ready mix truck drums. The drum blends the slurry & foam as it rotates. The blended CJFill-UW discharges via the chute directly into the placement area.

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Facing a similar challenge? Give us a shout or shoot us a text. Click the state marker for the location of your project for contact info for the appropriate rep.

Nashville Basement Abandonment

The Job

This Nashville basement abandonment project is located along Church Street, in downtown Nashville, Tennessee. A privately owned building was constructed inside of the basement of a previous building, but with a smaller footprint. Structural slabs spanning between 4′ and 20′ from the original basement walls to the new basement walls served as a parking lot and public sidewalk.

The Challenge

As the structural slabs over the unused basement deteriorated, there were concerns about stability. Uses included a public sidewalk and parking/driveway area. The wall isolating the occupied space of the new building and the unoccupied area of basement was constructed of hollow clay block, metal studs & drywall. The maximum lateral load of any backfill material could only be 50PSF.

The Solution

CJGeo successfully completed this Nashville basement abandonment with 775CY of 25lb/cuft CJFill-Ultra Lightweight cellular concrete. CJGeoGeo used 2′ lifts to meet the maximum 50PSF liquid head limit on the containing wall.

To address the unreliability of ready mix availability, CJGeo used the dry batch generation process to make the CJFill-UL onsite. Dry batch generation blends dry bulk cement and water onsite using a custom batch plant, which also generates the preformed foam. The cement slurry and preformed foam pass through a static mixer to ensure a homogenous mixture.

Because the roof slab was close to 18″ thick, and had multiple cast in place beams, CJGeo worked with the customer to design a sacrificial vent pipe system. This minimized the number of holes to core through the slab, while ensuring continuous bearing of the vault roof on the cellular concrete fill material.

Prior to placement of the CJFill-UL, a shotcrete contractor coated the hollow clay block wall to make it grout tight.

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Facing a similar challenge? Give us a shout or shoot us a text. Click the state marker for the location of your project for contact info for the appropriate rep.

Steam Tunnel Lightweight Backfill

The Job

This steam tunnel lightweight backfill project is located at Western Carolina University, in Cullowhee, North Carolina. As part of the expansion and renovation of the steam plant, a section of existing steam tunnel needed to be uncovered to install a new wall. The wall needed to be backfilled, and due to the condition of the tunnel, the lighter the backfill the better.

The Challenge

The site was exceptionally tight, and the location was more than 30 minutes from the closest ready mix plant. The backfill depth was nearly 15 feet, but the project was only about 1200CY. So, doing 2′ lifts would have been slow and expensive.

To effectively eliminate axial loads from the tunnel, the structural engineer designed a cardboard void form system to temporarily support precast planks on top of the tunnel, which was approximately 5′ wide and 5′ tall. The planks extended about 18 inches beyond the sides of the tunnel. The void forms were wrapped in plastic. This ensured they wouldn’t be fouled by the CJFill-Ultra Lightweight cellular concrete during the pour. After the CJFill-UL was in place, the ends of the beams were encapsulated in, and bearing on, the cellular concrete, while spanning over the tunnel, and transferring the load of the backfill above the tunnel away from it.

The Solution

CJGeo proposed a CJFill-UL as a value improvement over the organic foaming agent cellular concrete that was specified. The architect and structural engineer approved the proposed change.

CJGeo mobilized a four person crew and a 200CY/hour mobile batch plant, and completed the steam tunnel lightweight backfill work in three pours over two days. The CJFill-UL was generated using a synthetic foaming agent. It can be placed up to 20 thick at a time, and is generated onsite directly from bulk cement, so isn’t dependent on ready mix plant locations.

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Facing a similar challenge? Give us a shout or shoot us a text. Click the state marker for the location of your project for contact info for the appropriate rep.

Savannah Tunnel Abandonment

The Job

This Savannah tunnel abandonment job is part of the JW Marriott Plant Riverside conversion. It’s an adaptive reuse hotel project of a decommissioned power plant in Savannah, Georgia. As a thermal generation facility, there are extensive water tunnels below the structure. The cast in place tunnels are part of the piled foundation.

The Challenge

As part of the conversion from thermal power generation to luxury hotel, the tunnels posed a maintenance concern. Due to concerns about inducing settlement with traditional flowable fill, the designer specified EPS Geofoam blocks. These would have effectively eliminated loads, but were deemed impossible to install.

The Solution

Someone onsite had heard of cellular concrete, so reached out to CJGeo. CJGeo evaluated the layout of the tunnels, isolation methods from the river, and designed a mix which would ensure both complete filling of the structures without adding any additional load.

CJGeo placed approximately 930CY of 20lb/cuft CJFill-UL cellular concrete over a period of three days to complete the Savannah tunnel abandonment. Because CJFill-UL is highly mobile, demo debris from the access holes for building bulkheads was left in the tunnels, and encapsulated with the CJFill-UL.

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Facing a similar challenge? Give us a shout or shoot us a text. Click the state marker for the location of your project for contact info for the appropriate rep.

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