Lightweight Plaza Fill
The Job
Lightweight plaza fill for a private age restricted high rise new build in Tysons Corner, Virginia. Tysons Corner was historically an office heavy area of Fairfax County, but this project, along with many others, is increasing the amount of residential real estate in the area.
The Challenge
To manage dead loads over the four story parking deck, while achieving a landscape design requiring up to five feet of fill, the designer specified 20lb/cuft CJFill-High Permeability cellular concrete for the plaza fill material. The material had to be permeable, and placed up to 600′ from the closest access point for a plant. The deck elevation is about 30′ above the laydown area.
The total square footage of placement needed to be around 17,000 square feet. EPS foam blocks were an alternative fill material. However, EPS would have been exceptionally time consuming and expensive to install.
The Solution
CJGeo mobilized a 200CY/hour dry batch plant and crew, who generated up to 500CY/day for placement via hoses and a boom pump to successfully fill the plaza areas. Total project volume for this lightweight plaza fill was approximately 2200CY.
All material is onsite from dry bulk cement, with zero exposure to the hit or miss ready mix concrete market. An onsite cement storage pig allows overnight raw material delivery and staging, to eliminate traffic disruption.
The 20lb/cuft CJFill-High Permeability Low Density Controlled Low Strength Material placement was formed by the site concrete contractor. After the CJFill-HP had set, the site concrete contractor poured exposed aggregate sidewalks directly on top of the CJFill-HP. Other areas of the deck were backfilled with engineered lightweight soil, and then planted with extensive landscaping.
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Hollow Abutment Filling
The Job
This hollow abutment filling project is located in Buckland, Massachusetts. Buckland is a small town on the east end of the Berkshires. The bridge conveys a rural highway over a drinking water impoundment. As part of a bridge rehabilitation for MassDOT, two hollow abutments were specified for filling. This would turn the structural approach/departure slabs into slab on grade. The alternative would have been to completely replace the structures. Filling them with traditional weight backfill would have caused significant settlement.
The Challenge
It was up to 30′ from the bottom of slab to the underlying soil which had originally been installed to backfill the abutments. The lightest possible material capable of providing sufficient support to the pavement was required. This would reduce the loads applied to the bridge from the backfill. Due to the very constrained access (a few cored holes through the deck, and a few square foot port cut into each abutment face), the lightweight material had to be self-consolidating (placed as a fluid).
Due to integrated beams for the structural slabs, there were 12 different individual pockets which were up to 2′ tall. Each had to be vent independently during the final lift. Four of were under live traffic because the road had to have one lane open at all times.
The Solution
CJGeo worked with the general contractor to formulate a plan to vent the individual pockets from outside of the open lanes. This helps to ensure a complete fill without requiring a complete road closure. Over the course of two mobilizations, CJGeo placed 2,840CY of 25lb/cuft CJFill-Ultra Lightweight to fill the abutments.
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8″ Pipe Abandonment
The Job
This 8″ pipe abandonment project is located outside of Washington, DC. As part of continuing waterline replacements, a utility contractor in Fort Washington, Maryland, needed to abandon 10,600LF of 8″ water main. The utility and DOT both require grouting of all utilities 6″ and larger taken out of service.
The Challenge
In order to minimize the number of placement points, the grout needed to be exceptionally mobile.
The Solution
CJGeo proposed a 30lb/cuft CJFill-Ultra Lightweight (CJFill-UL) cellular grout, and worked with the client to design a grouting plan that would allow grouting all 10,600LF of pipe from just three access points. CJGeo performed the grouting over a period of two days, with no additional excavation required from the customer other than their original tie ins/disconnects.
By cutting the pipe at three locations, it was split into roughly equal segments. Each of around two thousand six hundred feet. 30lb/cuft CJFill-Ultra Lightweight is easily pumpable this distance without yield loss.
To do this same work with flowable fill would have required approximately thirty five access points. This would be to split the pipe into roughly thirty six segments around three hundred feet, each. Even then, pumping flowable fill three hundred feet through eight inch pipe is very difficult. By using CJFill-Ultra Lightweight for this pipe abandonment project, the general contractor saved about two weeks off of their schedule, and tens of thousands of dollars.
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Union County Annular Space Grouting
The Job
This Union County annular space grouting project is located in North Carolina, near Charlotte. Due to a rapidly increasing population, Union County, North Carolina installed a new raw water intake. It required a nearly 11 mile long raw water line to supply a water treatment plant.
The Challenge
There are dozens of road crossings along the alignment. 17 crossings are jack & bore, and require annular space grouting per NCDOT requirements. Given the length of the project, there weren’t any ready mix providers who could cover this entire annular space grouting in North Carolina project.
The Solution
CJGeo has multiple NCDOT approved mix designs, for CJFill-UL. CJGeo sourced material from two different ready mix providers. Each annular space on all crossings was grouted per NCDOT requirements. CJGeo has approved mix designs with the North Carolina Department of Transportation that cover the entire state. From the Outer Banks to Asheville, Raleigh/Durham, Wilmington & Charlotte, CJGeo has you covered.
The density for this work was 30lb/cuft CJFill-Ultra Lightweight. 30lb/cuft CJFill-Ultra Lightweight breaks above NCDOT’s minimum 125psi at 28 day unconfined compressive strength requirement for annular space grout. Because the project volume on this job is relatively low per crossing, CJGeo used ready mix for the raw slurry. Ready mix typically isn’t best for large placements. But for small, spread out placements like this project, is a great fit.
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24″ Water Main Abandonment
The Job
This 24″ water main abandonment project is located in Fairfax, Virginia. Fairfax County is part of the rapidly expanding Northern Virginia region. As part of a large transportation project, 2000 linear feet of 24″ water main were being relocated out of a highway right-of-way.
The Challenge
Due to phasing, the old water main was located under the existing roadway and could not be accessed, except for at one point near the center of the run. So, the abandonment grout had to meet VDOT’s minimum strength requirements for flowable fill, and be pumpable up to 1100LF at low pressure. VDOT’s minimum 28 day unconfined compressive strength requirement is 30psi.
The Solution
CJGeo grouted each run of pipe using 30lb/cuft CJFill-Ultra Lightweight low density controlled low strength material. Each CJFill-UL placement took fewer than two hours, and required no additional traffic control, disruptions to other construction activities, or help from the utility contractor after they installed the bulkheads.
The 28 day compressive strength of 30lb/cuft CJFill-Ultra Lightweight cellular grout is 150psi. This significantly exceeds VDOT’s minimum compressive strength for controlled low strength material (flowable fill).
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Facing a similar challenge to this 24″ water main abandonment project that CJGeo completed using CJFill-Ultra Lightweight cellular concrete? 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.
Grain Silo Tunnel Backfilling
The Job
This grain silo tunnel backfilling project is located in Tampa, Florida. As part of a redevelopment project in downtown Tampa, Florida, a large grain milling facility was moving operations from the downtown port to a new facility further down Tampa Bay.
The Challenge
The facility is immediately adjacent to Tampa Bay. To minimize flood risks, the the entire structure is above grade. This includes the 8′ tall unloading conveyor tunnels. The structure was bears on a mat slab cast over thousands of auger cast piles. The unloading tunnels were only about 10% of each silos footprint. So, the areas long side of the tunnels needed to be filled.
Due to the slipform construction, there was very limited access. So the backfill material around the tunnels needed to be pumpable. Flowable fill was an option, but is very heavy. The design build contractor identified cellular concrete as a potential backfill material. This could save nearly 1ksf of dead load off of the mat foundation.
The Solution
CJGeo worked with the design builder to create a mix design that would minimize the amount of dead load on the foundation, while providing adequate support for the bin floor when fully loaded with grain. Over the course of a few weeks, CJGeo crews placed nearly 7200CY of 25lb/cuft CJFill-Ultra Lightweight cellular concrete. Rodbusters were able to start setting steel the day after completion of the final lift in each of the silos.
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Neuse River Annular Grouting
The Job
This annular grouting project is located in North Carolina. The City of Raleigh’s Neuse River East Parallel Interceptor project involves the installation of miles of large diameter gravity sewer. Two road crossings required 120″ tunnels for installation of the 96″ HOBAS pipe.
The Challenge
While neither tunnel was very long, due to the 10′ diameter tunnels, grouting needed to be performed in two lifts. This allowed buoyancy control of the HOBAS carrier pipes to be maintained with partial water filling, and eliminated the need to perform hold down blocking during the carrier pipe installation.
The Solution
CJGeo proposed an NCDOT approved 40lb/cuft CJFill-Standard cellular grout mix due to passage through an NCDOT right of way, and then grouted the two tunnels each in two lifts. Fill was confirmed with uniform grout vented out the 12 o’clock vent position at the far end of each tunnel.
By using cellular grout instead of a traditional high unit weight grout, CJGeo designed three lifts out of the placement. This is because carrier pipe buoyancy is a function of the displaced mass. When the grout is less than 1/3 the density of traditional grout, deeper lifts are possible without floating the new carrier.
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Dairy Branch Annular Space Grouting
The Job
CJGeo’s Dairy Branch annular space grouting project is located in North Carolina. Charlotte Water’s Dairy Branch Tributary Sewer project is an approximately $30mm capacity improvement project to address increasing population density.
The Challenge
As part of the project, the tunneling contractor mined a 430LF tunnel ranging from 58″ bore to a four foot arch. The carrier pipe was 36″ ductile iron, and required annular space grouting using a mix which wouldn’t float the carrier pipe, and would be able to entirely fill the tunnel at low pressure.
The Solution
CJGeo proposed an NCDOT approved cellular grout mix due to passage through an NCDOT right of way. This annular space mix design is weighs around 30lb/cuft, so falls withing CJGeo’s CJFill-Ultra Lightweight range. The tunnel was completely dry, so displacing water was not a concern. It took less than two hours to place all 275 cubic yards of grout into the annulus.
Peak pumping pressure was less than five psi. Complete water filling of the carrier pipe provided more than a two time factor of safety for buoyancy control. CJFill-Ultra Lightweight cellular grout is sometimes called foamed concrete fill.
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New York Annular Space Grouting
The Job
This New York annular space grouting work is part of the Bay Park Conveyance Project. The Bay Park Conveyance Project is using a combination of microtunneling and slip-lining. This is to redirect effluent discharge from Western Bay to an existing ocean outfall several miles away.
The Challenge
Approximately 7 miles of the discharge pipe is being sliplined into an existing 72″ riveted iron pipe. The pipe runs underneath the Sunset Highway. Access pits are between 700LF & 3000LF apart, requiring annular space grouting placements ranging from 200CY to 850CY.
Due to maintenance of traffic concerns, all grouting is night work. There is nowhere to stage materials onsite.
The Solution
Working with the design and construction teams, CJGeo designed a 30lb/cuft, 150psi at 28 day compressive strength CJFill-Ultra Lightweight cellular grout for the annular space grouting. By using dry batch mixing onsite, CJGeo is able to achieve the compressive strength required, and place the distances required in the very short nightly placement windows.
Pipe jacking is the installation method for the carrier pipe, so there are no casing spacers. Because there are no casing spacers, water filling is the buoyancy control method. With water fill and a grout density significantly lower than water, the carrier uplift factor of safety is approximately 2.5 times.
To address material logistics, each night’s cement consumption is staged locally during the day. The cement is then brought to each placement location during the pours.
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9.5kCY MSE wall backfill
The Job
This MSE wall backfill project is located on Interstate 95 north of Baltimore, Maryland. The Express Toll Lanes will add extra capacity up the center of the existing roadway. This project is adjacent to a previous CJGeo project, where we placed 2,000 CY of CJFill-Ultra Lightweight cellular concrete as part of the Clayton Road Overpass reconstruction.
The Challenge
A 96″ diameter PCCP raw water supply line runs parallel to Interstate 95 along most of the project length. Originally, there was quite a bit of room between the roadway and the water line. However, as lanes are added, it’s gotten closer and closer to the PCCP water line. As part of this project, there are extensive ramp and embankment sections. They are immediately adjacent to the waterline, which is not in a condition to see any increase in loading.
To address this, designers specified lightweight material for the MSE wall backfill material.
The CJFill MSE Wall Backfill Solution
Originally designed for backfilling with Lightweight Expanded Shale Aggregate (LESA). CJGeo worked with the contractor to develop a hybrid MSE wall backfill material of 30lb/cuft cellular concrete and traditional weight 57 stone.
The relative depths of the two materials was selected so that the average density of the mass was equal to that of an entirely LESA backfill. This resulted in only needing roughly 2/3 the volume of lightweight backfill material.
Lightweight backfill is rarely less expensive as soil or traditional aggregates. However, by leveraging the very low unit weight of cellular concrete, a blended solution was possible that saved significant amounts of money.
CJGeo generated as much 500CY per day of CJFill-Ultra Lightweight to backfill the wall. The 30lb/cuft wet cast density provides adequate pull out resistance, and 140psi of unconfined compressive strength at 28 days.
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