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.
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.
During construction of a commercial development, 200LF of 16″ CPVC waterline was installed via jack and bore, through a 36″ casing.
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 without damaging the delicate carrier pipe material.
CJGeo successfully complete the project in a few hours. Uniform material vented at the far end confirming complete fill.
A utility contractor installing 500LF of 48″ HDPE reline pipe through a 63″ CMP culvert required annular space grouting done at very low installation pressure yet able to ensure complete filling of the washouts outside of the CMP. This HDPE reline annular space grouting project is located in Baltimore, Maryland.
Due to traffic control limitations, only one end of the pipe was accessible for grouting. Therefore, all grout installation was done with up to 200LF of pumping to get to the bulkhead and then up to 500 feet of travel through the annulus via sacrificial grout tubes. Bulkhead leaks usually result from extensive voids outside of the host pipe. This pipe’s invert corrosion posed unique challenges for containing the annular space grout.
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. Using cellular concrete for annular space grouting was specified by the HDPE slip lining pipe manufacturer.
CJGeo successfully performed this HDPE reline annular space grouting project over two days, in two lifts. Multiple lifts reduces heat of hydration and carrier buoyancy. The cellular concrete filled all of the voids outside of the host pipe. The peak pressure at the pump did not exceed 15PSI throughout the project. Therefore, the project was successfully completed without floating, deflecting, or damaging the HDPE slip line pipe.
CJGeo placed 30PCF wet cast density cellular concrete, with a 125psi compressive strength for this project. With a 24 hour penetration exceeding 50psi, 30PCF cellular concrete reduces buoyancy with its low unit weight, provides adequate strength, and rapid stability.
A 30″ brick sewer in New Jersey started to unravel during an open excavation point repair. The municipal engineer directed the utility contractor to use welded HDPE pipe to reline the sewer instead of finishing the open cut point repair. This North Jersey annular space grouting project is located in Paterson, New Jersey.
The HDPE slip lining contractor had four requirements for grouting.
- No more than 10psi grouting pressure, as measured at the bulkheads
- A mix which minimized carrier buoyancy
- Three day turnaround from notification to completion
- 200psi strength at 28 days
CJGeo proposed 38PCF wet cast density cellular concrete for the annular space grouting. Cellular concrete is highly flowable. High flowability ensures low installation pressure. 38PCF cellular concrete reduces exerts 60% less buoyancy force compared to traditional weight grout. 38PCF cellular concrete reaches approximately 250psi at 28 days.
CJGeo mobilized to the site with two days’ notice. The CJGeo cellular concrete crew used continuous generation to generate and place the 38PCF cellular concrete to complete this North Jersey annular space grouting project. Peak pressure at the bulkheads never exceeded 5psi. All 500LF of annulus was grouted in a single day, between four different manholes (three sections).
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.
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.
During construction of a data center in Richmond, Virginia, two bores were done under a roadway so that communication duct banks could cross into the facility. Each casing was 48″ in diameter, and approximately 100LF.
The jack & bore contractor was required to grout the annular space after sliding in the conduit bundles. The dense conduit bundles and relatively fragile pipes led them to doubt the ability of a traditional flowable fill grout to completely travel the length of the bores without damaging the conduits.
CJGeo proposed performing the annular space grouting using cellular concrete. CJGeo had perviously pumped cellular concrete on the same site more than 1600LF to abandon a run of 30″ sewer line, so the contractor knew that grouting 100 foot long runs wouldn’t be a problem for cellular concrete.
CJGeo mobilized a single cellular concrete crew to the site, and grouted two bores in less than a day. All of the grouting was completed at less than 5psi of grouting pressure. Both bores were confirmed full when uniform cellular concrete vented at the 12 o’clock position on the opposite side of the road.
38lb/cuft cellular concrete was used to meet the 28 day break strength requirement of 200psi. CJGeo used continuous generation to generate and place the cellular concrete; the whole project was completed using just two loads of ready mix slurry.
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 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.