Secaucus Lightweight Fill
The Job
This Secaucus lightweight fill project is located just across the Hudson River from Manhattan. It’s part of a completely gut of an existing 100,000 square foot distribution and logistics building. While the ground in Secaucus is terrible, the real estate is valuable because of its close proximity to New York City, and also at the core of the dense, urban North Jersey market.
The Challenge
Since original construction in the 1970s, the floor of the building has settled nearly two feet. This is due to underlying compressible, organic soils. As the underlying soils consolidated, and the floor settled, two subsequent floors were poured on top of the existing floor. Varying thicknesses of recycled concrete and other base materials were used to level over the differentially settled previous floors in preparation for the new floor pours.
The goal of the full gut was to build a food grade space. This is to bring the building into a more profitable sector. To do this, minimizing the amount of future settlement was important. Reports from multiple consulting geotechs in the past recommended undercutting and lightweight fill placement as a viable option for achieving this goal. The CMAR reached out to CJGeo about designing and implementing an undercut and lightweight fill program. This was based on our experience on similar projects in the Secaucus area.
The Solution
CJGeo’s inhouse geotechnical engineer worked with the CMAR’s geotechnical consultant. We used RocScience’s Settle 3 program to design an undercut program that would bring anticipated settlement to no more than 1.5 inches. Given the global subsidence of the area, along with rising ground water levels and increasing flood chances, buoyancy was also a design consideration. The total system (floor, base stone & lightweight fill) had to have a minimum 1.1 factor of safety against uplift in fully inundated condition. As an added measure of safety, given the very large footprint of the fill, limited permeability soils immediately below the lightweight fill, and disruptions associated with any buoyancy, CJGeo recommended not factoring infiltration into reduced buoyancy.
The final design includes a 42 inch undercut, followed by placement of 32 inches of CJFill-Ultra Lightweight foamed concrete fill. CJGeo mobilized a single dry batch plant to the site, and placed approximately 8,500 cubic yards of CJFill-Ultra Lightweight material. Production was as high as 1100 cubic yards per day.
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Wet Well Lightweight Fill
The Job
This wet well lightweight fill project is located at HRSD’s Nansemond Treatment Plant, in Suffolk, Virginia. As part of an extensive capital improvement project, the Nansemond Treatment Plant is being upgraded to accept increased flows. The additional flow will be coming via the Hampton Roads Sanitation District’s Hampton Roads Crossing (HRX) project.
As part of the upgrades, a large wet well requires abandonment filling. The structure bears on deep foundation piles, and underlying soils are extremely poor. Therefore, the structure requires low density, self-consolidating fill instead of traditional flowable fill.
The Challenge
The Construction Manager At Risk evaluated multiple lightweight fill materials. Geofoam would provide the least additional load, but due to safety concerns from access into the structure, would not be practical. Foamed glass aggregate fell below maximum allowable densities, but would be difficult to place and compact in the tight space. Expanded shale would be too heavy, and very difficult to place and compact.
The Solution
CJGeo worked with the CMAR, along with the geotechnical and structural engineers to design a fill program which would minimize density, maximize safety, and be optimal for cost and schedule.
CJGeo mobilized a 200cy/hour cellular grout plant to the site, and placed 430 cubic yards of 25lb/cuft CJFill-Ultra Lightweight foamed concrete fill. To manage lateral loads on the walls during placement, two ten foot deep lifts brought the fill to finish elevation.
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NYC Cellular Concrete
The Job
This NYC cellular concrete project is located at the William McCray Playground in Manhattan. The existing playground had experienced significant subsidence, which damaged the already outdated equipment.
The entire playground was demolished, in order to install a new updated facility, including play equipment, basketball court and spray equipment.
The Challenge
Design documents called for three feet of 25lb/cuft lightweight fill material over roughly 4,000 square feet of the site. Two options were given to contractors; 25lb/cuft cellular concrete or foamed glass aggregate.
Logistics for any work in Manhattan are tricky. Challenges include truck traffic limitations, constraints on work time and noise, and the narrow, congested streets. There was no room on the site for any stockpiles.
The Solution
The customer determined using 25lb/cuft CJFill-Ultra Lightweight fill by CJGeo would be the lowest risk, most economical, and fastest method allowable by specification. Because the equipment for generating foamed concrete fill is mobile and compact, the tight site wasn’t a problem.
CJGeo brought in just four loads of cement in order to generate the approximately 550 cubic yards of foamed concrete material. Cold temperatures didn’t affect the operation; it froze the night between the two pours, and also the night afterwards. No tenting or protection is required.
The day following the second pour, the customer was able to start placing pavement base on top of the cellular concrete.
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Lightweight Fill Over Waterline
The Job
This lightweight fill over waterline project is located north of Baltimore, Maryland, in Edgewood. It is part of a modernization and widening of I-95. This includes replacement of multiple bridges crossing I-95, including Clayton Road. Clayton Road is a rural, two lane roadway. However, I-95 in this area is a very heavily traveled, critical piece of the east coast megalopolis infrastructure.
About half of the City of Baltimore’s raw water supply parallels I-95 in this area. It runs through a 108″ PCCP raw water main that originates at the Susquehanna River, a few miles north of the project site.
The Challenge
As part of replacing the Clayton Road bridge over I-95, the bridge clearance was increased. To facilitate this, the approach/departure embankments had to come up a few feet. On the west end, this was not a problem; there are no underlying utilities or compressible soils.
On the east end of the bridge, however, the 108″ PCCP raw water main passes under the roadway embankment, in an area where grades needed to come up by an average of three feet. The pipe cannot see any additional load.
The Solution
Two potential solutions for this challenge are using lightweight fill to balance loads, or install a pile-supported load transfer slab bridging over the pipe. Lightweight fill was the fastest and most economical option.
CJGeo mobilized a single dry batch plant to the site. Over the course of six days onsite CJGeo poured 2,000 cubic yards of CJFill-Ultra Lightweight load reducing fill. The fill mass is roughly 10 feet thick at the deepest. At 25lb/cuft, this balances the loads within the zone of influence of the pipe. The pipe sees no increase in loads despite up to 4 feet of additional elevation over it.
Due to CJGeo’s exclusive use of high shear mixing, the contractor was able to place aggregate base on top of the CJFill-UL the following day.
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T Wall Lightweight Backfill
The Job
This T wall lightweight backfill project is located in Boston, Massachusetts. The bridge is located on the Lowell Line, within the MBTA‘s Commuter Rail Maintenance Facility.
The Challenge
CJGeo has been involved in this alternative delivery project since 2020, helping to optimize the use of CJFill-Ultra Lightweight fill to facilitate constructing a new embankment over underlying compressible soils.
In this specific location on the project, curved T walls were installed along the curved alignment (different radius) of the existing embankment. A sheet pile SOE retains the existing embankment. Due to highly irregular spaces, limited access, lightweight aggregate, such as foamed glass, would be exceptionally difficult to install and ensure adequate compaction.
The Solution
CJGeo proposed 26lb/cuft CJFill-Ultra Lightweight as the optimal material for the T wall lightweight backfill. The lowest 4′ is CJFill-High Permeability. Because CJFill is a self consolidating fill, there’s no compaction required. This practically eliminates chances of backfill consolidation. On a curved, relatively high speed commuter rail alignment, settlement could be quite risky if it were to occur.
For the first phase, CJGeo mobilized a single dry batch cellular grout plant. The work took a total of five days to place the foamed concrete.
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Hobas Pipe Backfilling
The Job
This Hobas pipe backfilling project is located in Baltimore, Maryland. It is one of the last steps in an emergency storm drain collapse project.
The Challenge
The original design for this project was to slip line a roughly 100 linear foot length of 108″ brick sewer that had collapsed. There was a massive void above the pipe, which was going to be filled with CJFill-Ultra Lightweight after the new pipe was slid in. However, the soil collapsed and the repair turned into an open cut repair.
The pipe is more than 100 years old, and was installed in a rock trench, the walls of which were uneven and unstable. Extensive rock bolting and stabilization was installed to facilitate the installation of the pipe. In order to ensure uniform bedding and stability of the new pipe, Hobas and the EOR recommended backfilling the pipe to at least 1′ above the crown with self-consolidating fill.
150lb/cuft flowable fill would have resulted in tremendous uplift forces on the pipe, unless installed in impracticably thin layers.
The Solution
CJGeo proposed cellular grout as an alternative, in order to reduce the uplift while decreasing the number of lifts.
Due to water infiltration near the invert, the first lift was done using 65lb/cuft CJFill-Under Water. Once the first lift was in place, the placement was switched to CJFill-Standard.
All material was generated onsite from bulk cement using CJGeo’s colloidal dry batch generation process.
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Underground Storage Tank Fill
The Job
This underground storage tank fill project by CJGeo is located at a food manufacturing facility near Harrisonburg, Virginia. The tank is 30 thousand gallons, and designed to store diesel to feed backup power generation for the facility. As part of an equipment upgrade, the tank is no longer in use, and had to be filled.
The Challenge
The best way to address unused underground storage tanks that aren’t removable is to fill them. If left empty and out of mind, abandoned empty tanks can cause serious problems, such as sudden collapse, which can significantly affect operations. Unfilled, out of use tanks can also accumulate groundwater, leading to potential environmental liabilities.
The Solution
CJGeo proposed 30lb/cuft CJFill-Ultra Lightweight (CJFill-UL) to fill the tank. CJFill-Ultra Lightweight is easily hand and machine excavatable to ensure that when the tank is removed in a few years that it’s not difficult.
While easily hand excavatable, CJFill-Ultra Lightweight still provides more than adequate compressive strength. In this case, total loads were just a few hundred pounds per square foot, whereas the CJFill material provides more than 17ksf of unconfined compressive strength. The American Concrete Institute publishes a removability modulus calculation which helps to quantify the ease of removal of controlled low strength materials, read more about it and how it relates to cellular concrete here.
It took CJGeo less than an hour to completely fill this tank. Confirmation of complete fill was uniform material venting from the tank vent ports.
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Tunnel Adit Fill
The Job
This tunnel adit fill project is part of the Purple Line project outside of Washington, DC. Specifically, the adit is located at the pedestrian connection between the Purple Line project and WMATA’s Bethesda station on the Red Line.
The Challenge
Plans call to connect the Purple Line to the Red Line using an adit constructed during the original construction of the Red Line. The adit is approximately 30 feet wide by a 35 foot tall arch. During preparation to blast from a shaft dropped adjacent to the station, a fault was identified passing through the adit.
The construction and design teams were concerned about stability of the adit during blasting operations as the Purple Line access tunnel was excavated towards it. The team determined that filling the adit to plug and stabilize it during blasting would be the most risk appropriate move.
Filling the adit would fulfill the design challenge of stabilizing the rock during blasting. However, it created the following challenges:
- the tunnel adit fill material would need to be removed after blasting was completed
- the adit is approximately 100 feet below grade
- there is very limited space up top
- material couldn’t segregate, and had to be pumped approximately 250 feet in addition to the 100 foot drop
The Solution
The tunnel engineer of record recommended CJGeo to the contractor. The EOR is familiar with CJGeo’s cellular grout generation and placement expertise, and thought that foamed concrete would be the lowest risk way to fill the adit, while facilitating excavation and removal afterwards.
CJGeo took five days onsite to fill the adit, in lifts up to eight vertical feet. Due to the potential dead load from the rock cover, 400psi CJFill-Standard was the material of choice. By using our colloidal mixing dry batch process, the material set off quickly, ensuring that it would not consolidate during cure as lower energy mixing methods can suffer from.
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Virginia Lightweight Fill
The Job
This Virginia lightweight fill installation is located Norfolk, Virginia. The placement is part of a low income housing development in an area subject to flooding. The site is located a few blocks from downtown Norfolk.
The Challenge
Like many coastal cities, much of the ground in Norfolk is infill. On this site, fill material was entirely uncontrolled. It included construction debris, organics, and silty sands. In order to bring the finish floor elevations above flood elevation, the site needed to come up by nearly eight feet in some areas.
The Solution
CJGeo worked with the structural engineer to design a lightweight backfill program that would help reduce anticipated settlements. After stone columns were installed across the site, the CMU building walls were built on poured footings. After the walls were in place, CJGeo filled the entire building pads with Ultra Lightweight CJFill, with an average density of 25lb/cuft.
CJGeo batched CJFill-Ultra Lightweight with a 80psi at 28 day minimum compressive strength using the dry batch process onsite, and placed at times more than 1,000 cubic yards per day.
Once the CJFill-Ultra Lightweight was in place, plumbers trenched in plumbing, and placed twelve inches of sand on top of the CJFill-Ultra Lightweight. The work took around two weeks, using the dry batch generation method.
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Basement Wall Load Reducing Fill
The Job
This basement wall load reducing fill project is located in Lexington, Virginia, on a campus of Washington & Lee University. The scope is part of a new academic building construction project. The building will house the Williams School of Commerce, Economics & Politics.
The Challenge
The building is on a sloping site. The front of the building will be slab on grade, and the back half of the building will be a walk-out basement level. The transition between the two floors is an approximately fifteen foot tall wall with two 90’s.
The basement wall is designed to be braced by the floors and building. However, the floors & building couldn’t be built until the wall backfill was in place. In order to backfill the wall, it would need load reducing fill, or it would need temporary bracing.
The Solution
A structural engineer recommended the general contractor reach out to CJGeo about backfilling the wall with CJFill-Ultra Lightweight low density fill. Working with the structural EOR, geotech EOR & general contractor, CJGeo developed a backfilling plan that would allow backfilling the wall over three days while eliminating the need for temporary bracing.
CJGeo poured three lifts, each about 4.5′ deep. A dry batch process plant running at up to 200 cubic yards per hour and using preformed foam from Aerix Industries backfilled the wall in three days.
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