Banner

Mass Lightweight Fill

By applying unique solutions to increase the safety and longevity of our environment.

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.

The Challenge

As part of the project, all activities were being moved above grade. A 12′ deep tank below the building floor needed to be filled before installing a new floor. The pit had been designed for holding water, and the majority of the pit was below ground water levels.

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 material.

Lightweight Temporary Dam Foundation

The Job

As part of flood proofing project a nuclear power plant, a temporary dam was designed for installation as needed between two large structures.

The Challenge

The cooling water pipes for a reactor passed under where the dam would need to be constructed in the case of a predicted flood. If placed, the dam would add up more load to the underlying cooling pipes than they were designed for.

The Solution

To reduce the load on the underlying pipes in case the dam needed to be placed, the designer elected to excavate 3′ of fill from above the pipes and replace it with 25lb/cuft CJFill-UL . To address buoyancy, given the minimal cover (2″ of asphalt), geogrid was cast into adjacent high density flowable fill, and then cast into the CJFill-UL.

CJGeo placed the material in two lifts.

RiverRenew Lightweight Fill

The Job

The City of Alexandria’s RiverRenew project is 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-HP18. The placements was done in a single, 6′ deep lift in less than an hour.

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.

Nashville Basement Abandonment

The Job

This privately owned building was constructed inside of the basement of a previous building, but with a smaller footprint. Structural slabs were poured spanning between 4′ and 20′ from the original basement walls to the new basement walls.

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 filled the basement with 775CY of CJFill-UL7.5. The placements was done in 2′ lifts to meet the maximum 50PSF liquid head limit.

Steam Tunnel Lightweight Backfill

The Job

As part of the expansion and renovation of the steam plant at Western Carolina University, 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.

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 work in three pours over two days. The CJFill-UL was generated using a synthetic foaming agent that 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.

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 work occurred as part of Segment 2.

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.

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.

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

Savannah Tunnel Abandonment

The Job

The JW Marriott Plant Riverside is 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 tunnels were cast in place during original construction, and integrated into the pile supported foundation.

The Challenge

As part of the conversion from thermal power generation to luxury hotel, the tunnels needed to be filled. 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. 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.

Nashville Basement Backfill

The Job

Nashville Yards is a block-wide new build project in downtown Nashville, Tennessee. With multiple underground levels of parking, the basement 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.

Veranda St Bridge Infill

The Job

Maine DOT’s Veranda Street Bridge Replacement Project, in Portland, Maine. Using rapid bridge replacement, the project took a three span bridge and converted it to a single span bridge.

The Challenge

To manage settlement due to up to 80′ of underlying WOH material, lightweight fill had to be used to infill two spans, and backfill the new abutments. The absolute lowest unit weight possible requirement led to a hybrid cellular concrete/EPS fill design. The bulk of the infill was performed using EPS blocks. However, due to the irregular surfaces, piers, etc., and the need for a lightweight load distribution slab, cellular concrete was integral to the design.

The Solution

Over two mobilizations, through snow and freezing temperatures, CJGeo placed 3200CY of 25lb/cuft CJFill cellular concrete for abutment backfilling and existing pier infills. A 778CY 30lb/cuft topping slab was then poured over the EPS fill masses.

Industrial Basement Abandonment

The Job

As part of an adaptive reuse project of an abandoned industrial site, the former onsite power plant’s stacks were being rehabilitated. Multiple tunnels and basement rooms needed to be completely filled.

The Challenge

Due to safety concerns, nobody could enter the basement. No as-builts were available. Camera inspection through holes cored in the ceiling showed significant numbers of passageways and obstructions. The fill material had to be exceptionally mobile, able to be placed in deep lifts, and as light as possible.

Fill density was a concern because the basement was up to 15′ deep. The structural and geotechnical consultants were concerned about inducing settlement if flowable fill (typically around 150lb/cuft) was used.

The Solution

CJGeo proposed 25lb/cuft cellular concrete for the fill material. Using onsite colloidal batching, CJGeo can place material up to 20′ deep in a single lift, without consolidation. Because the material is so lightweight, the entire 15′ deep basement could be filled for the same dead load as just two feet of flowable fill.

CJGeo mobilized a 150CY/hour dry batch plant to the site after staging 300 tons of cement onsite using our in-house cement pig & trucking operation. Without being affected by trucking or cement supply chain disruptions, CJGeo started placing immediately. Over four days onsite, CJGeo place 2700CY of material.

Top