Have a tricky pipe abandonment challenge? Don’t want to dig holes down the middle of a road every 100 feet to dump flowable fill into a pipe? We specialize in long run pipe abandonments. Whether it’s a 4″ conduit or a 96″ sanitary sewer, cellular concrete is an economical, reliable pipe abandonment material. CJGeo has abandoned up to 3500LF of pipe in a single stretch with no intermediate access points.
25PCF wet cast density cellular concrete is the most common pipe abandonment mix. This yields an average compressive strength of 70psi at 28 days. Higher densities can be used to achieve higher break strengths if required by project conditions. However, density & cost are positively correlated; 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, so in place material is entirely homogenous, so high factors of safety aren’t required to ensure adequate bearing capacity and/or long term stability.
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 relies on gravity to ensure complete fill, so is rarely used. Cellular concrete can easily be pumped 3000+ feet through abandoned pipes. Therefore, cellular concrete requires far fewer injection points than traditional flowable or pumpable fill.
Cellular concrete is economical for pipe abandonment because the majority of the mix is air bubbles. This decreases the material cost significantly.
Another cost savings benefit of cellular concrete is that it’s highly pumpable. We have done single access point abandonments in excess of 3500LF on pipes as small as 8″. This significantly reduces the number of access points which are required compared to traditional flowable fill installation. The installation pressure of cellular concrete is also much lower than flowable fill, which helps to ensure safer jobsites.
The lightweight mixes used for pipe abandonment generally have expansion ratios of greater than 3 times. This significantly reduces the number of trucks onsite. This reduces job site congestion and allows other trades to work uninterrupted. For applications adjacent to roadways, it can significantly reduce traffic control expenses.
Flows Through Collapses
Cellular concrete easily abandons partially collapsed pipes. If water can pass through a collapsed area, cellular concrete can as well. Cellular concrete’s high flowability eliminates the need to drill or excavate down to intercept trapped sections pipe between collapses. Cellular concrete also fills all voids outside of collapsed pipes.
Cost of Pipe Abandonment Using Cellular Concrete
In most applications, the material and placement costs of cellular concrete and flowable fill are relatively close. The big savings are recognized by minimizing the amount of traffic control and excavation to access the pipe as frequently as flowable fill requires. For example, a 12″ gravity sewer abandonment with flowable fill may require an access point every 200LF. In urban environments this frequency can cause major problems and complications, such as adjacent utility strikes, traffic control and deep excavations in congested environments.
For many abandonment placements, CJGeo can hook one end of 2000LF or longer run of pipe and pump all day until grout comes out the other end.