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Project Profile N20DN003

Terefil® Used to Fill Redundant Stormwater Pipe Underneath Home

Pipe Decommissioning
Void Filling

The problem

When a local council on the NSW North Coast was upgrading its ageing stormwater network, a reinforced concrete pipe was found to be running directly underneath a residential property.

The council was looking to re-route the stormwater pipe outside the perimeter of the property as part of their stormwater upgrade works.

The section of pipe beneath the home was 40m long x 375mm wide. As it was impossible to remove the pipe without demolishing the home, the pipe needed to be filled with a structural fill material before being abandoned to prevent future issues from occurring. Should the underground pipe deteriorate and collapse, the soil surrounding the pipe would shift, potentially leading to the formation of underground voids, in turn putting the home’s foundations at risk of subsidence.

The council had arranged CCTV cameras to inspect the conditions inside the pipe before work commencing. The footage revealed that a pipe junction had been installed to the main stormwater pipe located directly underneath the home, with a second pipe intersecting the old stormwater pipe. Tree roots and debris had also infiltrated the cavity. The council approached Mainmark to help fill the stormwater pipe using an appropriate grout fill solution.

The solution

Mainmark was required to safely decommission the reinforced concrete stormwater pipe with a structurally sound and environmentally inert pipe fill solution.

The Result

Mainmark’s proprietary Teretek resin injection solution was identified as an ideal option to help improve the lifespan of the pavement slabs.

Mainmark commenced the project, working closely with council to arrange the necessary preliminary requirements such as securing the pipe end plates and installing breathers and injection fittings, before decommissioning the 40m stormwater pipe. The
council also needed to create a pipe bypass around the old section of pipe to ensure the stormwater would be diverted.
Mainmark injected approximately 5m3 of Terefil®, a proprietary lightweight cementitious grout, into the section of pipe that was to be abandoned. The grout was mixed to a specific density to ensure the pipe remained firmly in place.
Terefil is a highly flowable polymer modified cementitious grout that can be easily pumped over very long distances, making it an ideal solution for this site. The grout is a structural fill containing a uniformly distributed matrix of air bubbles generated by mixing the cement slurry with stable, pre-formed hydrocarbon foam. The cementitious product encapsulates the air bubbles, leaving a lightweight yet strong concrete mix that is far more stable than alternative concrete void fill materials.
The use of Terefil allowed the council to complete the pipe abandonment work without the need for
expensive excavation or creating any disruption to the homeowner. The project was successfully completed in a single day and within budget, to the council’s complete satisfaction.

Project Resources & Downloads

Terefil® Used to Fill Redundant Stormwater Pipe Underneath Home
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