New York Tub Crossing Lifting
The Job
Eight panels of StarTrack modular grade crossing tubs settled. As a result of the settlement multiple clips broke. This tub crossing lifting project was for a short line serving an industrial facility in Geneva, New York.
The Challenge
The crossing tubs settled, and when crossed by trucks, pumped water containing the subballast up between the tubs and adjacent pavement. The crossing was the only entrance into an industrial facility that took two trains per day. Because of limited onsite storage, rail service couldn’t be disrupted at all.
The Solution
CJGeo proposed grouting immediately below the panels, and also into the underlying disturbed subballast using CJGrout 48NHL geotechnical polyurethane grout. CJGeo performed the tub crossing lifting work without impacting rail traffic, and the facility was able to function normally throughout the repair, which took less than a day.
Polyurethane grouting with CJGrout is an excellent alternative to cement based grouting, because:
- CJGrout cures within a few minutes, so there are no limitations on rail traffic
- CJGrout is not brittle, so does not break down in dynamic environments like thin layers of cement-based grout tend to do
- CJGrout application is not weather dependent; in this case, it was snowing during installation
- CJGeo controls the entire CJGrout logistics process, so there’s no need to wait on ready mix trucks or coordinate deliveries of material that goes bad within a few hours of offsite mixing
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Pit Fill With Lightweight Flowable Fill
The Job
An abandoned water treatment plant at a federal facility was being rehabilitated and brought back into service. As part of the project, lightweight flowable fill was needed to fill a 12′ deep tank below the building floor needed to be filled before installing a new floor and equipment.
The Challenge
The majority of the pit is below ground water level. The original foundation design used a 62PCF fill density for the pits, presuming they would only ever hold water.
The backfill material also needed to completely encase a number of new micropiles installed for machine bases.
The designer had two competing interests–given the closeness of the water table to finish floor, avoid any buoyancy of the fill material, while using the lightest possible material to avoid inducing any settlement.
The Solution
CJGeo proposed filling the pit with CJFill-UW, at 70lbs/cuft. At 70lb/cuft, there are no uplift concerns, and the material is just barely denser than water, which helps minimize the amount of anticipated settlement. To help ensure future excavatability, CJGeo used a sanded base slurry (as opposed to the usual neat mix slurry) to generate 830CY of lightweight flowable fill material. The 28 day design strength was 150psi. The average 28 day tested compressive strength was 200psi. The removability modulus of the material is 0.75, which means the material is readily excavatable.
Traditional “lightweight” flowable fill is closer to 95lb/cuft. At 150psi, 95lb/cuft material has a removability modulus of 1.18. This is above ACI’s benchmark value of 1 for ease of excavatability.
For this project the CJFill-UW was generated by adding preformed foam to ready mix truck drums. The drum blends the slurry & foam as it rotates. The blended CJFill-UW discharges via the chute directly into the placement area.
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Lightweight Temporary Dam Foundation
The Job
This lightweight temporary dam foundation installation was part of flood proofing project a nuclear power plant. The temporary dam can be quickly installed between two large structures in the case of anticipated storm surge. This is to keep flood waters from inundating a sensitive area.
The Challenge
The cooling water pipes for a reactor pass under where the dam goes in the case of a predicted flood. If placed, the dam exceeds the design load of the underlying cooling pipes.
The Solution
The designer elected to excavate 3′ of fill from above the pipes and replace it with 25lb/cuft CJFill-UL . Removing 3′ of 120lb/cuft material and replacing it with 3′ of 25lb/cuft, reduces dead load by roughly 275lb/sqft. The 25lb/cuft material can float, however. So, to address buoyancy, given the minimal cover (2″ of asphalt), geogrid cast into surrounding high density flowable fill acts as a hold down.
CJGeo poured the lightweight temporary dam foundation in two lifts. To void being in a cold joint, the geogrid was placed on sewer bricks. This ensures at least 6″ of embedment in the top layer of CJFill. To assess the readiness of the CJFill-Ultra Lightweight for paving, CJGeo cast a test slab for the customer to run heavy equipment over prior to loading the production area.
This was the first project where CJGeo utilized geogrid for buoyancy control of cellular concrete.
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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 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.
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Nashville Basement Abandonment
The Job
This Nashville basement abandonment project is located along Church Street, in downtown Nashville, Tennessee. A privately owned building was constructed inside of the basement of a previous building, but with a smaller footprint. Structural slabs spanning between 4′ and 20′ from the original basement walls to the new basement walls served as a parking lot and public sidewalk.
The Challenge
As the structural slabs over the unused basement deteriorated, there were concerns about stability. Uses included a public sidewalk and parking/driveway area. The wall isolating the occupied space of the new building and the unoccupied area of basement was constructed of hollow clay block, metal studs & drywall. The maximum lateral load of any backfill material could only be 50PSF.
The Solution
CJGeo successfully completed this Nashville basement abandonment with 775CY of 25lb/cuft CJFill-Ultra Lightweight cellular concrete. CJGeoGeo used 2′ lifts to meet the maximum 50PSF liquid head limit on the containing wall.
To address the unreliability of ready mix availability, CJGeo used the dry batch generation process to make the CJFill-UL onsite. Dry batch generation blends dry bulk cement and water onsite using a custom batch plant, which also generates the preformed foam. The cement slurry and preformed foam pass through a static mixer to ensure a homogenous mixture.
Because the roof slab was close to 18″ thick, and had multiple cast in place beams, CJGeo worked with the customer to design a sacrificial vent pipe system. This minimized the number of holes to core through the slab, while ensuring continuous bearing of the vault roof on the cellular concrete fill material.
Prior to placement of the CJFill-UL, a shotcrete contractor coated the hollow clay block wall to make it grout tight.
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Valve Vault Infiltration Grouting
The Job
This valve vault infiltration grouting project is part of the Purple Line project in Maryland. A large diameter water line was relocated, with the tie-in done inside a 10′ diameter vault that was about 20′ deep. The vault structure, which is precast, and set inside a line plate shaft, was leaking at multiple joints and at a poured in place pipe penetration closure.
The Challenge
The vault structure wasn’t concentric in the shaft. This left little room to pour the closure around the pipe penetrations. One of the penetrations leaked, causing the structure to completely fill with water. Per specifications, it needed to be dry.
Most of the shaft was backfilled with 57 stone. Highly permeable backfill material can make water control grouting particularly difficult. When grouting to seal relatively tight leaks in a structure, the less permeable the adjacent soils the better. All grouts want to take the path of least resistance, and with highly permeable backfills, that often means traveling out into, and permeating, the backfill material instead of into tight cracks and water passageways.
The Solution
CJGeo proposed grouting the infiltration points with CJGrout-35NHV61. 35NHV61 is a hydroinsensitive, plural component geotechnical polyurethane, certified for potable water contact. 35NHV61 is a moderately mobile grout, selected to minimize mobility into the 57 stone backfill and reduce material loss during grouting.
CJGeo mobilized a three person crew to the site, and performed the valve vault infiltration grouting over a few hours.
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Steam Tunnel Lightweight Backfill
The Job
This steam tunnel lightweight backfill project is located at Western Carolina University, in Cullowhee, North Carolina. As part of the expansion and renovation of the steam plant, a section of existing steam tunnel needed to be uncovered to install a new wall. The wall needed to be backfilled, and due to the condition of the tunnel, the lighter the backfill the better.
The Challenge
The site was exceptionally tight, and the location was more than 30 minutes from the closest ready mix plant. The backfill depth was nearly 15 feet, but the project was only about 1200CY. So, doing 2′ lifts would have been slow and expensive.
To effectively eliminate axial loads from the tunnel, the structural engineer designed a cardboard void form system to temporarily support precast planks on top of the tunnel, which was approximately 5′ wide and 5′ tall. The planks extended about 18 inches beyond the sides of the tunnel. The void forms were wrapped in plastic. This ensured they wouldn’t be fouled by the CJFill-Ultra Lightweight cellular concrete during the pour. After the CJFill-UL was in place, the ends of the beams were encapsulated in, and bearing on, the cellular concrete, while spanning over the tunnel, and transferring the load of the backfill above the tunnel away from it.
The Solution
CJGeo proposed a CJFill-UL as a value improvement over the organic foaming agent cellular concrete that was specified. The architect and structural engineer approved the proposed change.
CJGeo mobilized a four person crew and a 200CY/hour mobile batch plant, and completed the steam tunnel lightweight backfill work in three pours over two days. The CJFill-UL was generated using a synthetic foaming agent. It can be placed up to 20 thick at a time, and is generated onsite directly from bulk cement, so isn’t dependent on ready mix plant locations.
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