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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Pennsylvania Pipe Abandonment
The Job
This Pennsylvania pipe abandonment project is located at a drinking water reservoir near York, Pennsylvania. As part of a dam reconstruction, the existing outfall pipe was specified for grouted abandonment.
The Challenge
The existing outfall pipe is 48″ cast iron pipe, and approximately 200 feet long. The pipe passes approximately 45 feet below the crest of the earthen embankment, concrete core dam structure. To ensure that the pipe would not serve as a conduit for water after abandonment, the specification calls for cellular grout with a maximum permeability of 1×10-6 centimeters per second.
During design, there were concerns about leaks in the pipe draining out some of the cellular concrete after placement stopped, but before it reached initial set. To address this, a secondary grouting program using chemical grout was designed to top off any void volume in the outfall pipe after the cellular grout set.
The Solution
CJGeo proposed using 60lb/cuft CJFill-Standard cellular grout for the abandonment. 60lb/cuft CJFill-ST exceeds the minimum compressive strength requirement, and has less than 1×10-6 cm/sec permeability.
CJGeo mobilized a dry batch cellular grout plant to the site to complete this Pennsylvania pipe abandonment project. The crew performed the grouting in fewer than two hours. The dry batch plant generates the 60lb/cuft cellular grout onsite directly from bulk cement powder.
Placement was through sacrificial grout pipes installed by the general contractor. The GC also constructed masonry bulkheads on both ends of the structure.
Exploratory holes drilled in the bulkheads the following day confirmed uniform fill, and no need for the secondary grouting work.
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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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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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Michigan Water Main Abandonment
The Job
This Michigan water main abandonment project is located in Saginaw, Michigan. It is a 2900LF of 8″ grouted abandonment for the local municipality.
The Challenge
The utility contractor who installed the replacement water main was required to fill the old pipe with grout after tying in the new pipe. Because of the relatively small diameter, they were going to have to dig approximately 15 access holes if they used traditional flowable fill. The contractor really didn’t want to have to do that. So, they sought a highly mobile grout that would eliminate the need for digging access points.
The Solution
CJGeo proposed using CJFill-Ultra Lightweight cellular grout for this Michigan water main abandonment. Because the project volume is approximately 40 cubic yards. CJGeo proposed using wet batch generation, with a local ready mix provider supplying the raw slurry.
Wet batch generation is well suited for projects like this because the volume of slurry required is much less than a full load of cement. The equipment for wet batch generation is very portable–typically just two pickup trucks, one pulling a 20′ trailer with equipment.
Confirmation of fill for this Michigan water main abandonment project was material venting a fire hydrant at the far end of the placement. Pumping pressures were less than 20psi for the duration of the grouting process.
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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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Sheet Pile Joint Sealing
The Job
This sheet pile joint sealing work is part of the Thimble Shoals parallel tunnel project. The project is located between Islands 1 and 2 of the Chesapeake Bay Bridge Tunnel. The Chesapeake Bay Bridge Tunnel crosses the opening of the Chesapeake Bay, connecting Norfolk/Virginia Beach and the Eastern Shore.
The Challenge
Water was leaking out of a joint in the precast splash wall adjacent to the TBM slurry separation pit. Any time it rained, precipitation landing in the slurry pit would flow out of gaps in the sheet pile wall. It then passed through the roughly 3′ of soil between the sheet pile wall and splash wall, and then out through joints in the splash wall.
The Solution
CJGeo proposed using a single component, hydrophilic chemical grout to seal the joints. Hydrophilic grout is best for this particularly repair because:
- the area is rather dynamic, so hydrophilic’s ability to flex and stretch without tearing helped to ensure longevity
- the area is constantly exposed to moisture, so dimensional stability is not a concern.
A CJGeo chemical grouting crew of three people completed the sheet pile joint sealing repairs in less than a day. Some chemical grout extruded out through the joint in the splash wall. It was broken off flush with the surface and disposed of offsite.
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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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NY Grade Crossing Repair
The Job
10 panels of StarTrack modular grade crossing tubs settled in an urban street crossing owned by a short line. As a result of the settlement multiple clips broke. This caused the panels to pump.
The Challenge
The crossing tubs settled, and when crossed by trucks, pumped water containing the sub-ballast up between the tubs and adjacent pavement. The adjacent track also settled significantly.
The Solution
CJGeo proposed grouting immediately below the panels, and also into the underlying disturbed subballast using CJGrout 48NHL geotechnical polyurethane grout.
The CJGrout 48NHL was injected through 5/8″ holes drilled through the panels. The settlement pattern of each panel determines the specific hole spacing. It takes about five minutes for the grout to cure to 95% of its ultimate strength. After grouting, it’s important to tamp the approaches. Because the rails are clipped, lifting the panels lifts the rails & ties in the approaches. If the approaches aren’t tamped, the crossing can teeter totter, which is bad. Tamping is done immediately after grouting, and preferably before any rail traffic resumption.
CJGeo performed the StarTrack modular grade crossing repair without impacting rail traffic. The facility was able to function normally throughout the repair, which took less than a day.
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