1100 feet of pile-supported 34″ PCCP water line over a drinking water reservoir needed to be relined. 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 which had to be addressed prior to grouting. Work was complicated by a seasonal light display, which limited access hours to the job site. All work had to be performed over the drinking water reservoir.
The designer specified 55PCF wet cast density 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. The carrier pipe was completely filled with water during the grouting work.
Newport News, Virginia Due to failure of the PCCP internal concrete layer, grout injection had to be performed from the bulkheaded ends and also through the pipe wall, over water. All venting was performed over water. CJGeo completed the 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.
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.
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.
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 cellular concrete. The peak pressure at the pump did not exceed 5PSI throughout the project.
The pavement of a rural road outside of Williamsburg, Virginia collapsed suddenly. The pavement was adjacent to a golf cart tunnel, but there was nothing apparently wrong with the cart tunnel. VDOT closed the road to perform exploratory excavation. The exploratory excavation revealed a partially-collapsed RCP culvert pipe running adjacent to the golf cart tunnel. This required emergency pipe abandonment.
CJGeo had to mobilize with very little notice. The proposed grout had to have the ability to flow through the unknown obstructions in the collapsed RCP, and also out into any voids outside of the collapsed pipe.
CJGeo proposed cellular concrete due to its highly flowable characteristics. Cellular concrete is excellent for ensuring complete fills of collapsed or compromised pipes.
CJGeo mobilized to the site within one day and completed the emergency pipe abandonment in less than two hours. The road was opened back up to traffic immediately afterward.
A utility contractor in Rochester, New York, was tasked with abandoning nearly 30,000LF of 8″ oil-filled steel power conduit. After pulling the electrical lines and removing the oil, the contractor had to completely fill the lines with grout.
There are very few access points for high voltage power conduits. There were multiple runs over 3,500LF on this project, and it was neither safe nor practical to excavate down to the line at the frequent intervals required to fill the conduit with flowable fill.
CJGeo proposed abandoning the conduit with cellular concrete. Cellular concrete is an exceptionally high mobility grout, and can easily be pumped thousands of feet at a time, at low pressure. Through careful planning with the client, CJGeo broke down the placement into 9 different runs, ranging from 200LF to 3800LF. Each placement utilized existing access points, such as vaults & terminations.
CJGeo successfully abandoned each run of conduit. Pumping pressures never exceeded 30psi, and uniform grout showed at the vent end of each run to confirm complete fill. The work was performed over the winter, including multiple placements below freezing, and during the snow. The cellular concrete was generated using Aerlite preformed foam, by Aerix Industries, and continuous generation wet batching.
CSX crews were surfacing the mainline track in Baltimore when the tamping equipment struck an object immediately below the ties. Investigation revealed that it was a manhole associated with nearly 6000LF of 36″ water main primarily running immediately below the tracks. The municipality relocated the waterline but was faced with the challenge of abandoning the pipe from just two intermediate points. There were three sections of pipe; 1200LF, 1600LF & 2900LF. Various solutions were floated, including threading sacrificial tubing and grouting on the way out, but none were economical or could guarantee a pipe abandonment below the railroad.
The project designer, OBG, identified cellular concrete as a potential solution to the problem and reached out to CJGeo to determine its feasibility. CJGeo confirmed the appropriateness of cellular concrete and set out to create a grouting plan. Coordination between the utility contractor and slurry provider (the site was too small to set up a batch plant) was crucial to ensure that the runs of pipe were all successfully filled in a single shot each. With train frequencies of 3-4 per hour, if the operation didn’t work and the pipes were only partially filled, there was no opportunity to create intermediate access points to finish grouting a section of pipe.
Based on the required bearing capacity and production requirements, CJGeo proposed 22lb/cuft cellular concrete for abandonment. With a 25psi break strength at 28 days, the mix provided the required strength, met the CSX utility occupancy standard for abandonment, and maximized expansion in order to ensure the longest run, which required nearly 1000CY of the finished product, could be grouting in a single shot.
CJGeo mobilized a 150CY/hour cellular concrete crew to the site and performed the two shorter runs the first week. The project was broken into two different weeks due to the criticality of ensuring the longest run was filled completely without issue. The first two runs allowed CJGeo, the GC, railway flaggers, railway operations, and the slurry provider the opportunity to work out any kinks in operations during the lower risk placements.
The following Tuesday, starting at 0600, Chaney Enterprises delivered the first of 24 loads of slurry. Completeness of fill was confirmed by uniform cellular concrete venting out the far end of each placement. Overall, the work was completed in three days. CJGeo generated & pumped a total of 1710 cubic yards of cellular concrete to successfully complete the abandonment.
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.
Due to the relatively long run and delicate PVC carrier pipes, CJGeo proposed using cellular concrete for the annular space grouting. 45lb/cuft non-pervious cellular concrete generated using Aerlite preformed foam was proposed to achieve the owner’s requirement of 250psi at 28 days.
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, and uniform cellular concrete was vented at the far end of the casing, confirming a complete fill.
28 day breaks confirmed that CJGeo exceeded the break strength requirement.
As part of the construction of a pedestrian underpass at the Medical Center WMATA station, an open cut tunnel was installed. The tunnel crossed under MD-355, but over the underlying Metro Red Line tunnel. To maintain vehicular traffic during construction, a temporary bridge was constructed spanning the H-pile & lagging open cut walls.
After the tunnel was completed, the 7′ of space between the top of the new pedestrian tunnel and the bottom of the temporary bridge had to be filled. Numerous utilities, including gas transmission mains, a power vault & duct bank, municipal water, gravity sewer, and numerous communication duct banks and lines all passed through the fill area. The tunnel designers had planned on lightweight fill material being used for the majority of the backfill in order to reduce loads on the new pedestrian tunnel.
The extensive utilities and limited working space made other lightweight fill materials such as EPS blocks and lightweight aggregate impractical to place. The Clark Foundations project team reached out to CJGeo to come up with a pumpable lightweight fill solution.
CJGeo proposed using cellular concrete for the lightweight backfill. Cellular concrete had a few distinct advantages:
- Unit weight: the 30lb/cuft density met the designer’s requirement for unit weight, and also reduced buoyancy of to-be-embedded utilities
- Strength: the 125psi at 28 days strength far exceeded the requirement, and allowed for nearly immediate final backfill & paving
- Safety: since cellular concrete is pumped into place, just a few hours of labor were required in the tunnel to set the grout placement pipes
- Constructibility: aside from being lightweight, the primary concern was ensuring that all utilities were fully encapsulated and that there were no voids left. Since the fill had to go to within 12″ of the bottom of the temporary bridge beams, this would have been exceptionally difficult with any type of non-pumped lightweight fill.
CJGeo mobilized a single cellular concrete crew to the site, capable of producing up to 150CY/hour of cellular concrete. Over the course of three days, CJGeo placed 990CY of 30lb/cuft non-pervious cellular concrete, using Aerlite preformed foam. The placement schedule was primarily driven by DOT-imposed maximum lift thicknesses. Placement into the tunnel was done via sacrificial tubes suspended from the bridge decking, in addition to hose discharge into the tunnel ends.
7 day breaks on the cellular concrete exceeded the minimum strength for backfilling. This allowed the customer to stay on their targeted schedule.
The Sandston area, just outside of Richmond, Virginia, is at the crossroads of major north/south data transmission lines, and transoceanic data transmission lines. As a result, a number of large data centers are in the area or being planned & constructed.
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.
CJGeo mobilized a cellular grouting crew to the site and grouted 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 cellular concrete was used to achieve the design strength of 200psi at 28 days.
As 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 backfill grouting.
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, which helps to ensure proper alignment and minimize any chances of damage during grouting.
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, indicating that the cellular concrete had exfiltrated through the liner plate joints and was flowing outside of the liner plate.
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.
CJGeo confined that cellular concrete would be an excellent alternative to the problematic grout that was originally planned. To meet the 1,000psi requirement at 28 days, CJGeo proposed a 60lb/cuft neat mix cellular concrete, 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 easily pumped at low pressure for long distances
- economics–the 400CY project volume could be placed in two days instead of eight
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. Up to 400LF of 3″ sacrificial grouting pipe had been run in from each end. These sacrificial pipes were used for both venting and placement during grouting operations.