Atlanta cellular concrete
The Job
This Atlanta cellular concrete installation is part of Atlanta Watershed Management’s Niles Avenue Sewer Improvements project. The project took approximately 2500LF of microtunneling to install a new 18″ sewer main.
The Challenge
A 72″ microtunnel was chosen, which required approximately 1200CY of annular space grouting. Operations were challenged by the pandemic hitting in the middle of the project.
The Solution
CJGeo proposed 30lb/cuft CJFill-UL cellular grout for the annular space grout. This allowed the contractor to avoid mechanical buoyancy control during grouting operations during single lift grouting. Buoyancy control of the carrier was one of the driving factors for using CJFill-Ultra Lightweight for this Atlanta cellular concrete project. Because the tunnels had a good amount of slope on them, grouting in multiple stages would have been impractical. Flowable fill would have floated the carrier pipe, even if it was full of water.
Over two mobilizations, CJGeo generated the cellular concrete grout onsite using preformed foam from Aerix Industries and placed it via shafts which were up to 40 feet deep. CJGeo chose wet batch generation due to the project volumes.
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Garden State Parkway grouting
The Job
This Garden State Parkway grouting project is located near Middletown, New Jersey. As part of ongoing large diameter culvert rehabilitations and replacements, four new bored stormwater crossings and the original culvert they replaced needed to be grouted. The tunnels ranged from 120″ down to 74″, for a total of 312CY, and the abandonment required 405CY.
The Challenge
Grout needed to meet the minimum strength requirements of the owner, and ideally needed to be light enough to facilitate single lift annular space grouting.
The Solution
CJGeo’s preconstruction team worked with the general contractor to design a grouting program which facilitated single lift abandonment of the original culvert, and single lift grouting of the four various annular space runs. CJGeo utilized onsite dry batching to generate 30lb/cuft CJFill Ultra Lightweight cellular concrete.
CJFill is a type of Low Density Controlled Low Strength Material, or LD-CLSM. The “low density” comes from using preformed foam, in this case Aerlite-iX, as a substitute for aggregate. This significantly reduces the unit weight, which exponentially increases pumpability. In this case, all 405 cubic yards of abandonment grout were placeable at once.
Because CJFill LD-CLSM is significantly lighter than water, each annular space grouting run was doable in a single lift. Filling each carrier pipe partially with water was all it took to facilitate this.
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Union County Annular Space Grouting
The Job
This Union County annular space grouting project is located in North Carolina, near Charlotte. Due to a rapidly increasing population, Union County, North Carolina installed a new raw water intake. It required a nearly 11 mile long raw water line to supply a water treatment plant.
The Challenge
There are dozens of road crossings along the alignment. 17 crossings are jack & bore, and require annular space grouting per NCDOT requirements. Given the length of the project, there weren’t any ready mix providers who could cover this entire annular space grouting in North Carolina project.
The Solution
CJGeo has multiple NCDOT approved mix designs, for CJFill-UL. CJGeo sourced material from two different ready mix providers. Each annular space on all crossings was grouted per NCDOT requirements. CJGeo has approved mix designs with the North Carolina Department of Transportation that cover the entire state. From the Outer Banks to Asheville, Raleigh/Durham, Wilmington & Charlotte, CJGeo has you covered.
The density for this work was 30lb/cuft CJFill-Ultra Lightweight. 30lb/cuft CJFill-Ultra Lightweight breaks above NCDOT’s minimum 125psi at 28 day unconfined compressive strength requirement for annular space grout. Because the project volume on this job is relatively low per crossing, CJGeo used ready mix for the raw slurry. Ready mix typically isn’t best for large placements. But for small, spread out placements like this project, is a great fit.
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Neuse River Annular Grouting
The Job
This annular grouting project is located in North Carolina. The City of Raleigh’s Neuse River East Parallel Interceptor project involves the installation of miles of large diameter gravity sewer. Two road crossings required 120″ tunnels for installation of the 96″ HOBAS pipe.
The Challenge
While neither tunnel was very long, due to the 10′ diameter tunnels, grouting needed to be performed in two lifts. This allowed buoyancy control of the HOBAS carrier pipes to be maintained with partial water filling, and eliminated the need to perform hold down blocking during the carrier pipe installation.
The Solution
CJGeo proposed an NCDOT approved 40lb/cuft CJFill-Standard cellular grout mix due to passage through an NCDOT right of way, and then grouted the two tunnels each in two lifts. Fill was confirmed with uniform grout vented out the 12 o’clock vent position at the far end of each tunnel.
By using cellular grout instead of a traditional high unit weight grout, CJGeo designed three lifts out of the placement. This is because carrier pipe buoyancy is a function of the displaced mass. When the grout is less than 1/3 the density of traditional grout, deeper lifts are possible without floating the new carrier.
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Dairy Branch Annular Space Grouting
The Job
CJGeo’s Dairy Branch annular space grouting project is located in North Carolina. Charlotte Water’s Dairy Branch Tributary Sewer project is an approximately $30mm capacity improvement project to address increasing population density.
The Challenge
As part of the project, the tunneling contractor mined a 430LF tunnel ranging from 58″ bore to a four foot arch. The carrier pipe was 36″ ductile iron, and required annular space grouting using a mix which wouldn’t float the carrier pipe, and would be able to entirely fill the tunnel at low pressure.
The Solution
CJGeo proposed an NCDOT approved cellular grout mix due to passage through an NCDOT right of way. This annular space mix design is weighs around 30lb/cuft, so falls withing CJGeo’s CJFill-Ultra Lightweight range. The tunnel was completely dry, so displacing water was not a concern. It took less than two hours to place all 275 cubic yards of grout into the annulus.
Peak pumping pressure was less than five psi. Complete water filling of the carrier pipe provided more than a two time factor of safety for buoyancy control. CJFill-Ultra Lightweight cellular grout is sometimes called foamed concrete fill.
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New York Annular Space Grouting
The Job
This New York annular space grouting work is part of the Bay Park Conveyance Project. The Bay Park Conveyance Project is using a combination of microtunneling and slip-lining. This is to redirect effluent discharge from Western Bay to an existing ocean outfall several miles away.
The Challenge
Approximately 7 miles of the discharge pipe is being sliplined into an existing 72″ riveted iron pipe. The pipe runs underneath the Sunset Highway. Access pits are between 700LF & 3000LF apart, requiring annular space grouting placements ranging from 200CY to 850CY.
Due to maintenance of traffic concerns, all grouting is night work. There is nowhere to stage materials onsite.
The Solution
Working with the design and construction teams, CJGeo designed a 30lb/cuft, 150psi at 28 day compressive strength CJFill-Ultra Lightweight cellular grout for the annular space grouting. By using dry batch mixing onsite, CJGeo is able to achieve the compressive strength required, and place the distances required in the very short nightly placement windows.
Pipe jacking is the installation method for the carrier pipe, so there are no casing spacers. Because there are no casing spacers, water filling is the buoyancy control method. With water fill and a grout density significantly lower than water, the carrier uplift factor of safety is approximately 2.5 times.
To address material logistics, each night’s cement consumption is staged locally during the day. The cement is then brought to each placement location during the foamed concrete pours.
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SW Florida Annular Space Grouting
The Job
This Florida annular space grouting project by CJGeo is located in For Myers, Florida. The work is part of the City of Fort Myers’s South AWWTF Reclaimed Water Transmission Main. The goal of the project is to facilitate the beneficial reuse of treated wastewater, primarily for uses such as irrigation which historically utilized drinking water.
The Challenge
The majority of this pipeline uses open cut installation. However at two road crossings with extensive existing buried utilities, trenchless installation is most appropriate. The first crossing is 170 linear feet. The second crossing is 607 linear feet. Each tunnel is 52 inches in diameter steel. The reclaimed water line is 32 inch diameter ductile iron pipe.
The Solution
The tunneling contractor for this project was under contract to provide turn key installation, including annular grouting. The tunneling contractor reached out to CJGeo, knowing that CJGeo’s CJFill cellular grout could:
- fill each annulus in a single lift
- not over-pressurize or damage the brand new carrier pipe
- not float the brand new carrier pipe
CJGeo took two days onsite to grout both tunnels (one day per tunnel). The final design for the grout on this Florida annular space grouting project was 38lb/cuft CJFill-Standard, with a 250psi unconfined compressive strength at 28 days. While the Florida DOT’s minimum strength for cellular grout is only 80psi at 28 days, the designer wanted a higher strength grout than the minimum acceptable by the DOT.
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Tennessee Annular Space Grouting
The Job
This Tennessee annular space grouting project is located in Brentwood. Brentwood is part of the Nashville metro area, which is rapidly expanding. As part of large water main installation, a 970′ tunnel, ranging from 60 to 78 inch diameter was mined through a small mountain. To ensure long term service improvements, a 42″ DIP water line occupies the tunnel.
The Challenge
The tunnel support is wood lagging, which is not permanent. Therefore, the annular space requires grouting to ensure long term stability of the new water line and adjacent ground.
Because the Nashville market is so hot, it’s really hard to get any concrete deliveries, let alone specialty mixes. The tunneling contractor knew that they would be hard pressed to self-perform the grouting using flowable fill. This was if they could even get material. So, they reached out to CJGeo about performing the annular space grouting with cellular grout made onsite with one of CJGeo’s custom mobile cellular batch plants.
The Solution
CJGeo proposed and installed 25lb/cuft CJFill-Ultra Lightweight cellular grout for the annular space grouting. By generating material onsite directly from bulk cement, using a dry batch plant, the 425CY annular space grouting took fewer than five hours.
Buoyancy control on this project was very easy. Because CJFill-Ultra Lightweight cellular grout is so much lighter than water, filling the carrier with water was sufficient to ballast the pipe against uplift during grouting. No casing spacers or top blocking needed. The American Concrete Institute classifies CJFill-Ultra Lightweight as low density controlled low strength material.
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Georgia Annular Space Grouting
The Job
This Georgia annular space grouting project is located in Athens, Georgia. The project involves three tunnels connecting four shafts. Tunnel lengths range from 116LF of 700LF, with diameters between 58.5″ ID to 9×9 arch segments.
The Challenge
In order to keep the carrier pipe from floating during grouting, the maximum allowable grout density was 70lb/cuft, and the minimum compressive strength was 200psi. Material had to be highly mobile, to facilitate placement through the 700LF of tunnel.
The Solution
CJGeo proposed 38lb/cuft cellular grout to the tunneling contractor. Over a period of three days, CJGeo batched and placed 1320CY of CJFill-Standard. Batching was performed utilizing an onsite dry mix plant, which was fed directly by bulk cement trailers. The minimizes the required laydown area on a very tight site.
Because of the very low grout density, the carrier pipe buoyancy control was simply water filling.
To address the transition from a round tunnel to an arch tunnel, CJGeo worked with tunneling contractor to design a sacrificial pipe venting system.
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NY Thruway HDD Annular Space Grouting
The Job
This HDD annular space grouting project is east of Buffalo, New York, under the New York Thruway. As part of distribution improvements, National Grid’s contractor bored 830LF through rock using HDD. The bore was 30″, with a 16″ HDPE casing, carrying three, 4″ HDPE conduits.
As part of the installation, the NY Thruway Authority call for casing back grouting, and the casing pipe’s annular space grout filling.
The Challenge
The proposed back-grout had to be:
- pumpable 830LF at very low pressure,
- dense enough to displace the 10 pound per gallon drilling mud, and
- provide sufficient strength to meet Thruway requirements.
The proposed annular space grout had to be:
- pumpable 830LF at very low pressure,
- light enough to not apply excessive pressure on the conduit pipes, and
- also provide sufficient strength to meet Thruway requirements.
The Solution
CJGeo proposed two different grout mixes to meet the project requirements. 85lb/cuft CJFill-Under Water casing backgrout for the displacement of the 10PPG (75lb/cuft) drilling mud. And 25lb/cuft CJFill-Ultra Lightweight annular space grout within the casing.
CJGeo’s crew mobilized to the site, and successfully performed the back-grouting and annular space grouting in a single day. A tremie pipe strapped to the HDD casing was used for the back grouting. By pumping the 85lb/cuft (11 pound per gallon) CJFill-Under Water to the low point, the drilling mud was floated out of the reamed hole annulus.
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