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Mass Lightweight Fill

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Massachusetts Lightweight Fill

The Job

This Massachusetts lightweight fill project is located at Boston’s Logan International Airport. It is part of Logan Forward continuing improvements to the airport.

The Challenge

As part of this project, the general contractor installed two cast-in-place barrier walls. The space between the barrier walls is between four and nine feet. The walls are curving, have non-vertical faces, and bear on a curving, non-horizontal existing podium slab. The gap between the walls needed to be filled in order to pour a housekeeping slab spanning between the walls.

This work is all on an existing podium structure. So, the fill density between the two walls had to be as low as possible.

The Solution

CJGeo proposed filling between the two walls with CJGrout 20SDB. 20SDB has a similar density and compressive strength to typical expanded polystyrene (EPS, or Geofoam) blocks. However, unlike geofoam blocks, 20SDB:

  • is pumped, so doesn’t require trimming, and fits to any shape
  • expanded onsite, so logistics are significantly simpler
  • cures within a few minutes, so is still quick
  • not affected by petroleum products

A CJGeo polyurethane grouting crew took a single shift onsite to install the 64 cubic yards of CJGrout 20SDB. The general contractor began installing the topping slab the next day.

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Facing a similar challenge to this Massachusetts lightweight fill project? Give us a call or send us an email by clicking on the state marker to locate the Preconstruction Manager that services your area.

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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Facing a similar challenge? Give us a shout or shoot us a text. Click the state marker for the location of your project for contact info for the appropriate rep.

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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Facing a similar challenge? Give us a shout or shoot us a text. Click the state marker for the location of your project for contact info for the appropriate rep.

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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Facing a similar challenge? Give us a shout or shoot us a text. Click the state marker for the location of your project for contact info for the appropriate rep.

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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Facing a similar challenge? Give us a shout or shoot us a text. Click the state marker for the location of your project for contact info for the appropriate rep.

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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Facing a similar challenge? Give us a shout or shoot us a text. Click the state marker for the location of your project for contact info for the appropriate rep.

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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Facing a similar challenge? Give us a shout or shoot us a text. Click the state marker for the location of your project for contact info for the appropriate rep.

I-64 Soundwall Backfill

The Job

VDOT’s I-64 widening project is a multi-phase widening of Interstate 64 between Richmond & Newport News. This soundwall backfill work occurred as part of Segment 2, near the Queen’s Creek bridge.

The Challenge

Approximately 150LF of a combination sound & retaining wall needed to retain more than 10′ of backfill. In order to keep the drilled foundation size consistent along the alignment, the backfill material needed to be significantly lighter than the soil backfill used in other segments, where there was minimal retained depth.

The material needed to be freely-draining and less than 40lb/cuft. To ensure proper drainage, the lightweight fill material couldn’t impact the function of the combination drain waterproofing system applied to the wall.

The Solution

CJGeo proposed backfilling the affected wall segments with 30lb/cuft CJFill-UL. Used extensively by VDOT for backfilling the retained zones of MSE walls, CJFill-UL provides significantly better bearing capacity than soils or aggregates, and once cured does not apply lateral loads to the structures it is placed against.

During installation, lateral pressure from the cellular concrete is simply the hydraulic head. Hydraulic head is calculated by multiplying the pour thickness, in this case 5′, by the wet cast density, here 30lb/cuft, so 150PSF. Because CJFill-Ultra Lightweight cellular concrete does not contain any aggregate, there is no internal friction to contribute towards lowering pressures.

CJGeo placed approximately 200CY of CJFill-UL for the soundwall backfill the wall in two pours, each approximately 5′ thick. The contractor was able to place the pavement base on top of the material the following day.

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Facing a similar challenge? Give us a shout or shoot us a text. Click the state marker for the location of your project for contact info for the appropriate rep.

Savannah Tunnel Abandonment

The Job

This Savannah tunnel abandonment job is part of the JW Marriott Plant Riverside conversion. It’s an adaptive reuse hotel project of a decommissioned power plant in Savannah, Georgia. As a thermal generation facility, there are extensive water tunnels below the structure. The cast in place tunnels are part of the piled foundation.

The Challenge

As part of the conversion from thermal power generation to luxury hotel, the tunnels posed a maintenance concern. Due to concerns about inducing settlement with traditional flowable fill, the designer specified EPS Geofoam blocks. These would have effectively eliminated loads, but were deemed impossible to install.

The Solution

Someone onsite had heard of cellular concrete, so reached out to CJGeo. CJGeo evaluated the layout of the tunnels, isolation methods from the river, and designed a mix which would ensure both complete filling of the structures without adding any additional load.

CJGeo placed approximately 930CY of 20lb/cuft CJFill-UL cellular concrete over a period of three days to complete the Savannah tunnel abandonment. Because CJFill-UL is highly mobile, demo debris from the access holes for building bulkheads was left in the tunnels, and encapsulated with the CJFill-UL.

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Facing a similar challenge? Give us a shout or shoot us a text. Click the state marker for the location of your project for contact info for the appropriate rep.

Nashville Basement Backfill

The Job

Nashville Yards is a block-wide new build project in downtown Nashville, Tennessee. With multiple underground levels of parking, this Nashville basement backfill excavation is more than 30′ below grade in spots. The excavation walls are a combination of blasted rock and soil nail walls.

The Challenge

The designer wanted to reduce lateral loading on the basement walls as much as possible. Due to the irregular face of the blasted rock & soil nail walls, lightweight aggregate would have been very difficult to install and compact, and would have applied lateral loads for the life of the structure. Flowable fill would have been easy to install, but applied too much lateral loading during installation if done in practical pour volumes.

The structural engineer determined that 25lb/cuft cellular concrete would be the best backfill material. The project volume was approximately 1500CY, and the maximum fill depth was 30′.

The Solution

CJGeo mobilized a mobile batch plant which uses colloidal mixing to the site. Due to the extremely high quality mixing, the crew placed CJFill-Ultra Lightweight up to 10′ deep per pour. This included three pours 10′ deep and 250CY each to complete this Nashville basement backfill project on time.

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Facing a similar challenge? Give us a shout or shoot us a text. Click the state marker for the location of your project for contact info for the appropriate rep.

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