Virginia Annular Space Grouting
THE JOB
1100 feet of pile-supported 34″ PCCP water line over a drinking water reservoir was being slip-lined. This Newport News, Virginia annular space grouting project was specified by the designer to use cellular concrete. The relining contractor used 30″ welded HDPE for the slip line, which then required annular space grouting.
There were multiple leaks at the joints between the PCCP sticks. Work was complicated by a seasonal light display, which limited access hours to the job site.
THE CHALLENGE
The designer specified 55PCF wet cast density CJFill-Standard cellular concrete for the annular space grouting. Cellular concrete is highly flowable. High flowability ensures low installation pressure, reduces flotation of lightweight carrier pipes, and ensures complete void filling outside of the host pipe. Using cellular concrete for annular space grouting was specified by the HDPE slip lining pipe manufacturer. Buoyancy control was by water fill of the carrier pipe.
Nearly every joint on the pipe was leaking. Each joint had to be grout tight prior to starting the grouting process.
THE SOLUTION
All venting was over water. CJGeo completed this Virginia annular space grouting project without introducing any contaminants to the drinking water reservoir.
The 55PCF cellular concrete provided a break strength of approximately 700psi at 28 days. Peak installation pressure was 18psi.
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Maryland Annular Space Grouting
THE JOB
A jack & bore contractor performed a 200LF, 54″ bore under an arterial highway. After sliding in a 48″ RCP carrier pipe (stormwater), the annular space required grouting. This Maryland annular space grouting project is located in Jessup.
THE CHALLENGE
Due to size limitations, only one end of the pipe was accessible for grouting. The length of the placement was approximately 200LF, so grout had to travel 200LF at low pressure while ensuring a complete fill.
THE SOLUTION
CJGeo proposed cellular concrete for the annular space grouting. Cellular concrete is highly flowable. High flowability ensures low installation pressure, reduces flotation of lightweight carrier pipes, and ensures complete void filling outside of the host pipe.
CJGeo successfully performed this Maryland annular space grouting project in a single day using CJFill-Ultra Lightweight cellular concrete. The peak pressure at the pump did not exceed 5PSI throughout the project.
Due to the relatively low volume, CJGeo used continuous wet batch generation for making the cellular concrete. With continuous wet batch generation, a ready mix company delivers the slurry. The ready mix truck discharges into a grout pump, and CJGeo injects the preformed foam continuously in line downstream of the pump.
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Fullerton Reservoir Annular Space Grouting
THE JOB
This reservoir annular space grouting project is located in Baltimore, Maryland. As part of the construction of a new drinking water reservoir for Baltimore County, Maryland, 140LF of 30″ jack & bore with a 12″ DIP water line and two 4″ PVC conduits required annular space grouting.
THE CHALLENGE
Due to the relatively long run and delicate PVC carrier pipes, CJGeo proposed using cellular concrete for the annular space grouting. 45lb/cuft CJFill-Standard cellular concrete generated using Aerlite preformed foam was proposed to achieve the owner’s requirement of 250psi at 28 days.
Carrier pipe buoyancy control is one of the most difficult elements of small diameter annular space grouting. In very large diameter placements, multiple lifts are practical, but in small diameter pipes, generally aren’t possible. When multi-lift grouting isn’t practical, having a grout density less than water (about 60 pounds per cubic foot) facilitates single lift grouting as long as the carrier pipes are full of water.
THE SOLUTION
In a short morning, they generated and placed 31 cubic yards of cellular concrete to successfully grout the annulus. Peak pumping pressure was less than 5psi. Confirmation of a complete fill was uniform material discharging from the 12 o’clock vent at the opposite end from placement.
Because the grout density was significantly less than the density of water, filling the carrier pipes with water controlled all buoyancy.
28 day breaks confirmed that CJGeo exceeded the break strength requirement.
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Communication Jack & Bore Grouting
The Job
The Sandston area, just outside of Richmond, Virginia, is at the crossroads of major north/south data transmission lines, and transoceanic data transmission lines. This jack & bore grouting was done to support a road crossing connecting two new data centers.
The Challenge
As part of the construction of a new, multi-billion dollar data center, a utility contractor bored two, 48″ steel casings under a roadway & adjacent wet utilities for a road crossing. Each of the casings had up to 20 different PVC conduits held in place using casing spacers. The contractor needed a grout that could be placed at minimal pressure while ensuring complete fill without damaging the conduits.
To avoid carrier pipe buoyancy, the maximum allowable grout density for the annular space grouting was 45lb/cuft.
The Solution
CJGeo mobilized a cellular grouting crew to the site and did the jack & bore grouting on both pipes in a single day. The peak grouting pressure was 5psi, and confirmation of fill was achieved when uniform cellular concrete was vented from the 12 o’clock position on the opposite end of each bore. 38PCF CJFill-ST was used to achieve the design strength of 200psi at 28 days.
CJFill-ST is heavier than CJFill-Ultra Lightweight, which is the most common cellular grout that CJGeo uses for annular space grouting. However, in the case, the municipality specified a higher compressive strength due to the proximity of multiple other critical utilities.
CJGeo used wet batch on this project due to the low volume and proximity of a ready mix plant. Wet batch typically has lower peak heat of hydration, which is helpful when grouting around PVC.
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Microtunnel Annular Space Grouting
The Job
This microtunnel annular space grouting project is part of a massive interstate expansion project in Charlotte, North Carolina. Seven micro tunnels were mined under I-77 to convey various utilities below the highway. Microtunneling was used, with casing diameters of 60″, along with a hand-mined tunnel lined with an 84″ tunnel liner plate.
Due to the length of runs, volumes required and strict NCDOT mix design requirements, the tunneling contractor reached out to CJGeo to explore cellular concrete as an option for the microtunnel annular space grouting.
The Challenge
CJGeo proposed performing the annular space grouting using 30lb/cuft cellular concrete. CJGeo has approved NCDOT mix designs for cellular concrete, which helped facilitate expedited submittal processing.
Cellular concrete was also advantageous from a carrier buoyancy perspective. The carrier pipes installed in each of the tunnels were all negatively buoyant in the grout. This helps to ensure proper alignment and minimize any chances of damage during grouting.
The Microtunnel Annular Space Grouting Solution
During the first mobilization, CJGeo placed 630CY of cellular concrete to grout the two tunnels over a period of three days. The 60″ tunnel was grouted in a single lift, the 84″ tunnel was grouted in two lifts.
Confirmation of complete fill was through venting of uniform cellular concrete at the far ends of each tunnel. Additionally, the 84″ tunnel liner plate structure had cellular concrete weeping out of the bulkhead on the exterior of the plate. This indicates that the cellular concrete had exfiltrated through the liner plate joints and was flowing outside of the liner plate.
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Tampa Microtunnel
THE JOB
As part of a large design-build utility rehabilitation and capacity improvement project, a 60″ micro tunnel was dug under an interstate. The tunnel was approximately 40 feet below grade, and 1050LF. Due to the length of the tunnel, traditional grouts were unlikely to be successfully placed for the annular space grouting. Concerns with traditional grouts included flowability, carrier pipe buoyancy, and high pumping pressures, compounded by a local shortage of flash, which was a critical component of the planned grout.
The tunneling contractor reached out to CJGeo to see if cellular concrete would be a feasible product for the annular space grouting. The project was located near Tampa, Florida.
THE CHALLENGE
CJGeo proposed cellular grout to avoid the challenges associated with fine aggregate based grouts. To meet the 1,000psi requirement at 28 days, CJGeo proposed a 60lb/cuft CJFill-Standard, generated using Aerlite preformed foam, and continuous generation.
Cellular concrete provided a few key benefits for this project:
- material supply–cellular concrete does not require fly ash in order to be highly mobile and pumpable
- low unit weight–by being less dense than water, cellular concrete does not cause the water-filled carrier to be buoyant
- flowability–cellular concrete is very highly mobile
- economics–the 400CY project volume would take two days
THE SOLUTION
CJGeo mobilized a cellular concrete crew to the site. Using continuous generation and slurry from a local ready-mix supplier, CJGeo grouted the annulus completely. Completeness of fill was verified by uniform material venting from each of the vent and placement pipes at both ends of the tunnel.
Peak pumping pressure during grouting was approximately 8psi when grouted through the annulus.
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