Have a tricky abandonment grouting challenge? Don’t want to dig holes down the middle of a road every 100 feet to dump flowable fill into a pipe? CJGeo specializes in long run pipe abandonments. Whether it’s a 4″ conduit or a 96″ sanitary sewer, our project experience of thousands of miles of abandonment helps you reduce risk, reduce cost, and complete projects faster. CJGeo has abandoned up to 5600LF of pipe in a single stretch with no intermediate access points.
The Mechanics
Mix Design
25PCF wet cast density CJFill is the most common abandonment grouting mix. This yields an average compressive strength of 70psi at 28 days. Higher densities can achieve higher break strengths if required by project conditions. Density drives cost. The lower the density, the longer runs are achievable per placement point. And, the lower the cost per cubic yard in place. Unlike sanded flowable fill mixes, cellular concrete does not segregate. Therefore, high factors of safety aren’t required to ensure adequate bearing capacity and/or long term stability.
Placement Method for Pipe Abandonment
Depending on pipe diameter, slope, and existing access points, cellular concrete for pipe abandonment can be placed by dumping into manholes using a tremmie tube, or can be pumped. Tremmie placement into manholes is the most economical method. However, it relies on gravity to ensure complete fill, so is rarely used. Cellular concrete can easily be pumped up to 5000 feet through abandoned pipes. Therefore, cellular concrete requires far fewer injection points than traditional flowable or pumpable fill.
The Advantages
Risk Reduction
Two typical risks associated with traditional methods of pipe abandonment are:
- incomplete fills due to the physical limitations of flowable fill, and
- those associated with access point excavation, such as utility strikes.
The risk from incomplete fills is primarily related to the difficulty of pumping flowable fill. Since flowable fill relies heavily upon water content to ensure flowability, it is particularly prone to segregation. Aggregate segregation can block a pipe and effectively creating a plug. If the pump can’t overcome the plug, grouting has to stop.
Most utilities being abandoned are typically colocated with other utilities. Therefore, reducing excavation is almost always advantageous. Using cellular concrete virtually eliminates access point excavations due to very long pumping distances.
Cost Reduction
Because cellular concrete reduces the need for digging access points and the time it takes to perform abandonment grouting work, it tends to be significantly less expensive than traditional methods.
We perform turnkey abandonments; there’s no need for our customers to coordinate pump services, ready mix companies, etc.
Increase Speed
Our customers are almost always amazed by how quickly abandonments happen compared to self-performing with flowable fill. That 3000LF of 8″ that the owner said needed an access point every 200LF? It’s just 18 minutes of pumping with 25lb/cuft cellular concrete from a single point.
CJGeo’s dry batch generation plants are the size of ready mix trucks, but make up to 200 cubic yards per hour of grout. The plants have integrated pumps, so batch and place all at once. For smaller projects, CJGeo’s wet batch generation rigs can utilize ready mix to economically perform low volume placements.
Speak With An Expert
Facing an abandonment grouting challenge? Give us a shout or shoot us a text. Click the state marker for the location of the project for contact info for the appropriate rep.
