A sewer trunkline expansion in Richmond, Virginia required five bored road crossings ranging from 60″ to 72″.
Tunnel lengths ranged from 200LF to nearly 600LF, and were mined through rock using slurry microtunneling.
The design engineer required cellular concrete for annular space grouting due to run length, and buoyancy control of the carrier during grouting.
Not many; the longest run on this project, 600LF is a relatively short distance to push cellular concrete.
CJGeo proposed 38lb/cuft non-permeable cellular concrete to meet the designer’s 200psi 28 day compressive strength requirement.
Over four different mobilizations, CJGeo successfully placed approximately 900CY of annular space grout.
Cellular concrete generation was performed using wet batch continuous generation. Wet batch generation was chosen due to the relatively small daily volume of material placement and very constrained sites.
A stone arch bridge constructed in the 1800s was experiencing significant scour at the bases of the arch. This caused differential settlement of the structure, and deterioration of the wing walls.
The bridge, which was adjacent to an historic mill structure, could not be removed and replaced with a modern structure, it had to be rehabilitated in a fashion which preserved its historic nature.
The bridge was constructed on shallow stone foundations.
As part of rehabilitating the structure, structural engineers designed two new mass footings in the stream bed to underpin the edges of the stone arch. Then, to strengthen the arch, designed a 12″ thick reinforced concrete arch overlay on top of the stone arch for the full length/width of the bridge.
In order to compensate for this additional weight, designers determined that a lightweight fill material was needed to reduce the chances of inducing settlement.
Designers also evaluated remedial deep foundations, but determined that lightweight fill was the fastest and most economical solution.
After the structure had been rehabilitated, CJGeo installed 325CY of 30lb/cuft cellular concrete to backfill the structure. Placed in lifts up to 4 feet thick, the work was completed over a period of three days.
By using 30lb/cuft non-permeable cellular concrete, the dead load on the underlying soil decreased by up to 935lbs/sqft relative to compacted soil backfill.
Because cellular concrete is self-consolidating and can easily be pumped hundreds of feet, single side access was not a problem, and no compaction equipment was necessary.
A crew of two workers completed the pour using continuous wet batch generation. Wet batch generation was chosen due to the relatively small daily volume of material placement.
During widening of Interstate 66 year the interchange with US-15, nine new culverts were installed by jack and bore, and one via direct jacking. The carrier pipes were a mix of spiral metal, precast concrete, and corrugated HDPE, and ranged in length from 150 to 350 feet.
The boring contractor, who was responsible for grouting, was concerned about carrier pipe buoyancy during grouting, and also run length. All work had to be done from one side of the interstate highway (three lanes in each direction, plus full width shoulders and a median strip), as there was no access on the far side.
CJGeo proposed 30lb/cuft cellular concrete for the annular space grouting. Cellular concrete is the preferred material for annular space grouting because it is highly flowable, and reduces the chances of damage to carrier pipes in long placements. Its low unit weight also reduces carrier pipe buoyancy. CJGeo placed 350CY of cellular concrete to successfully complete the jack and bore annular space grouting over three different mobilizations.
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 slipline, 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 jobsite. 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.
CJGeo successfully completed this Newport News, Virginia annular space grouting project. 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 site 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 afterwards.
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 snow. The cellular concrete was generated using Aerlite preformed foam, by Aerix Industries, and continuous generation wet batching.
CSX crews were surfacing 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 water line, 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 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 the 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 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 waterline 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.
CJGeo mobilized an experience crew to the site. 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 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.