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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Michigan Water Main Abandonment
The Job
This Michigan water main abandonment project is located in Saginaw, Michigan. It is a 2900LF of 8″ grout fill 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. Aerix Industries supplied the preformed foam.
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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BNA Culvert Abandonment
The Job
As part of a Nashville International Airport’s BNA Vision project, several hundred feet of culvert needed to be filled with grout. The culvert abandonment work is part of installing a new drainage system to accommodate a new terminal.
The Challenge
Due to long runs with no intermediate access, the engineer specified cellular concrete as the abandonment grout. Access to the site was across an active taxiway, so the fewest deliveries possible was very important. The minimum design requirements were:
- 28 day compressive strength minimum = 100psi
- maximum wet cast density = 35lb/cuft
The Solution
To address the need to limit the number of deliveries, CJGeo performed the culvert abandonment using CJFill-UL . CJFill-UL is batched onsite directly from bulk cement. By using bulk cement onsite, there were no concerns about hot loads of ready mix. A single semi was able to deliver all the raw material for the placement.
Each of the runs on this project is greater than 250LF. By using highly mobile grout, there are no questions about the pipes being completely full. CJFill-UL is so mobile it will flow by gravity up to a few hundred feet. The material is always pumped. This allows for placement from either the high or low end of individual runs. Because the density of the material is very low, it takes very little additional pressure to place from the low end.
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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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Dumfries Pipe Abandonment
The Job
This utility relocation included abandonment grouting as part of a VDOT roadway reconstruction and realignment of US Route 1 in Dumfries, Virginia. This Dumfries pipe abandonment job is located in a rapidly growing town in Northern Virginia. US Route 1 is a major local traffic corridor, as well as a bailout route for I-95 congestion.
The Challenge
1,575LF of pipe, a combination of 54″ & 60″ needed to be completely filled with grout. Due to sequencing, the pipe was underneath new roadway at the time of abandonment. So, the fewer the number of access points, the better.
The Solution
CJGeo placed 995CY of 25lb/cuft CJFill-Ultra Lightweight cellular grout to completely fill the pipe run. The material was placed in a single day, from a single access point near the center of the pipe run.
To facilitate such a large placement in a single day on this Dumfries pipe abandonment job, CJGeo used dry batch generation. Dry batch generation mixed water with bulk cement onsite, using a mobile batch plant. CJGeo’s mobile batch plants are designed specifically to generate cellular concrete. They generate preformed foam at the same time as making the cement slurry. The preformed foam and cement slurry pass through an in line mixer, at up to 200CY/hour.
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Lightweight Pipe Backfill
The Job
This lightweight pipe backfill is part of the City of Alexandria’s RiverRenew project, its largest in history. The project includes installation of new interceptors, and a large CSO/conveyance tunnel.
The Challenge
A pile-supported, concrete-encased interceptor needed to be backfilled. Due to the pile support capacity, the maximum allowable density of the load reducing backfill was 90lb/cuft.
The Solution
To bring the average backfill density to 90lb/cuft, CJGeo proposed filling between the SOE & concrete encasement with 30lb/cuft CJFill-High Permeability (HP). CJFill-HP has very high permeability, so reduces buoyancy when saturated when compared to other lightweight fill materials. CJGeo successfully filled between the concrete encasement and SOE with 145CY of CJFill-HP. The placements was done in a single, 6′ deep lift in less than an hour.
To facilitate the fast placement speed, CJGeo used a mobile batch plant to generate the CJFill-High Permeability cellular grout onsite. Onsite generation blends dry, bulk cement onsite with water, using custom batch plants which also make generate the preformed foam on site. The cement slurry is around 110lb/cuft, and the preformed foam is around 2.5lb/cuft. CJGeo’s batch plants utilize colloidal mixing, which ensures the highest quality cement paste, and therefore the highest quality finished product possible.
The use of very low density material then allowed the client to backfill on top of the structure with normal unit weight material while maintaining the average 90lb/cuft density through the full depth of the fill column. Aerix Industries supplied the preformed foam.
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