Detroit Michigan Annular Space Grouting
The Job
This Detroit Michigan annular space grouting project is located near Van Dyke Avenue & 8 Mile Road. The project owner is Great Lakes Water Authority, and the project is part of the PCI-4 rehabilitation.
The Challenge
As part of the rehabilitation of this large diameter sewer, three different liner systems had to be installed. The longest section of single liner type is approximately 800 linear feet. The concrete sewer’s inner diameter is approximately 17.5 feet. The outer diameter of the liner that the installer subcontracted the annular space grouting to CJGeo on is approximately 16.5 feet.
Based on the theoretical average inside diameter of the existing sewer, the annulus is almost exactly one cubic yard per linear foot.
The Solution
The pipe runs at full charge at least once per day, so there was a high likelihood of accumulated water in the annulus. To displace this water and ensure consistent bearing of the pipe, CJGeo proposed 75lb/cuft CJFill-Under Water. While this density of CJFill cellular grout significantly exceeds the 300psi at 28 day compressive strength requirement, it facilitates displacing solids from the annulus.
To help manage buoyancy, once the first lift was in place, the wet cast density of the cellular concrete on this Detroit Michigan annular space grouting project was reduced to 45lb/cuft CJFill-Standard. Reducing the wet cast density significantly reduces uplift, which allows taller lifts.
CJGeo used an onsite dry mix batch plant to generate the cellular concrete and pump it up to five hundred feet in the sewer line.
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Texas Annular Space Grouting
The Job
This Texas annular space grouting project is located in Lockhart, Texas. It is a 42″ water pipeline for the Alliance Regional Water Authority.
The Challenge
The annular space grouting for this tunnel was specified for cellular concrete (sometimes called low density controlled low strength material). The minimum allowable compressive strength was 300psi at 28 days, when tested according to ASTM C495. The 42″ treated water pipeline was installed inside of a 60″ casing pipe.
The tunnel was approximately 460LF, and crossed under a frontage road and Texas State Highway 130, about 20 miles south of Austin.
The Solution
CJGeo proposed using onsite dry batch generation to make the cellular grout onsite. This has a few advantages over using ready mix (wet batch generation):
- purchasing cement directly from a cement plant bypasses ready mix plant’s cement allocation limits
- bulk material doesn’t go bad onsite
CJGeo used a relatively high water:cement ratio to account for temperatures of 105 degrees during the placement and generation. This helped to ensure that material did not prematurely set during placement, and allowed CJGeo to generate and place all of the 40lb/cuft CJFill-Standard cellular grout material in just three hours.
Confirmation of fill for this Texas annular space grouting project was material venting from the 12 o’clock vent on the far end of the tunnel. Pumping pressures were less than 15psi for the duration of the grouting process.
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Microtunnel Contact Grouting
The Job
This microtunnel contact grouting project is located in Clarksville, Tennessee. It is part of a new water intake structure along the Cumberland River to improve the reliability of the city’s municipal water source.
The Challenge
Based on the overcut of about an inch, and length of the 450 foot long tunnel, the contact grouting volume was approximately 50CY. In order to efficiently place the grout against the roughly 40′ of head from the river that that the tunnel terminates in, high volume, high quality mixing was required.
The tunneling contractor reached out to CJGeo to use onsite colloidal batching to generate grout quickly, safely, and without the risks of using ready mix.
The Solution
CJGeo proposed using a 0.55 water : cement ratio slurry generated onsite with colloidal mixing for the contact grout. While there were nearby ready mix plants that could have supplied the job, mixing neat grouts in transit mixer trucks typically does not uniformly wet out the cement. This can make it very difficult to pump, and typically results in highly variable mixes. Because the grout is the same as the cement slurry used for making CJFill cellular concrete, CJGeo used a cellular concrete batch plant with the foam generator turned off.
CJGeo batched and placed 50CY of slurry over about 2.5 hours to complete the microtunnel contact grouting. Placement of the grout was through 2″ ports, and the grout displaced both the lubricating bentonite slurry, and significant amounts of water. Due to the exceptionally high mobility of colloidally mixed neat cement grout, CJGeo’s crew was able to grout the entire length of the tunnel from two ports located just in from the launch shaft.
Grout communication was confirmed through lubricating ports, visual confirmation from the casing pipe drying due to heat of hydration, and divers in the river witnessing grout at the tremied bulkhead.
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Nashville Annular Space Grouting
The Job
This Nashville annular space grouting project is located at Nashville’s Central WWTP, which is undergoing extensive improvements to provide service to a growing population.
The Challenge
As part of an upgrade, 400LF of 66″ pipe was slip lined. Once the carrier pipe was selected, the space around its 57.1″ OD needed to be filled.
The Solution
CJGeo proposed using CJFill-ST at 45lb/cuft for this Nashville annular space grouting project. CJFill-ST is batched onsite directly from bulk cement, eliminating supply chain issues with ready mix.
Because the selected CJFill-ST only weigh 45lb/cuft, buoyancy control of the new carrier is simple. By filling it with water, it won’t float during grouting. This allowed CJGeo to grout the entire annulus in a single lift. Single lift grouting significantly reduces the likelihood of partial fills, fouled injection tubing, or trapped voids.
A CJGeo crew placed the 87CY of CJFill-ST in less than an hour to perform this Nashville annular space grouting project. CJFill-ST can be made two ways; wet batch or dry batch. With wet batch, a ready mix truck brings the base slurry to the site, and the foam is either added to the truck, or injected downstream of a pump. For dry batch generation, which was used here, a mobile batch plant mixes the cement and water onsite. The mixing quality using dry batch is significantly better than wet batch.
This project had a relatively high compressive strength requirement due to new foundation installation adjacent to the slip lined pipe. With cellular concrete, there are two ways to increase compressive strength–increase the cement content by increasing the density, or increasing the quality of the mix. Since annular space grouting projects are very sensitive to carrier pipe buoyancy control, increasing mix quality is a better option than increasing density. CJGeo’s three mobile batch plants all use high shear colloidal mixing. Colloidally generated material can have 28 day strengths up to two times ready mix batched material at the same density & cement content.
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Parsippany Annular Space Grouting
The Job
This Parsippany annular space grouting project is part of a microtunneled installation of 48″ sanitary line in two runs under an interstate. Each tunnel is 60″ diameter, one was 725LF, the other 530LF. They shared a shaft. The project’s goal is to replace an aging stretch of large diameter gravity sewer that runs parallel to the interstate.
The Challenge
The owner specified a grouted annular space for the tunnels. The long pumping distance and relatively tight annulus drove the need for a highly mobile, lightweight grout.
Cellular grout is advantageous for annular space grouting because:
- it’s primarily air, so takes little energy (pressure) to pump, which virtually eliminates risk of damaging the carrier pipe(s) during grouting
- it’s significantly lower density than traditional grouts, which reduces the buoyancy of carrier pipe(s)
- cellular grout is made onsite, reducing risk exposures from the ready mix supply chain when mosts placements are “you only get once chance to do this right” type of jobs
The Solution
CJGeo placed 270CY of 35lb/cuft CJFill-ST (36ksf unconfined compressive strength) cellular grout to fill the annulus on both tunnels. Because the shared shaft wasn’t easily accessible, grouting was performed from each end towards the shared shaft over two back to back days.
CJGeo used onsite dry batching to generate the cellular grout for this Parsippany annular space grouting project. Dry batch generation uses bulk cement, eliminating risks associated with the ready mix supply chain. Cellular grout made using the dry batch process is also much higher quality, which allows CJGeo to get higher strengths with lower densities. This lowers pumping pressure, buoyancy, and costs.
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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 grout onsite 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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