Sewer Pipe Decommissioning using Cement-Bentonite Grout

Case description

As part of the remediation of the Sydney Tarponds and Coke Ovens site, two large-diameter concrete drainage pipes were to be decommissioned by filling with low-strength cement grout.


A general contractor contacted Peter White for engineering assistance to develop a grouting plan and to prepare a list of required equipment and bill of materials for decommissioning of two drainage pipes.

Peter recommended a low-strength cement-bentonite grout mixture for this application to complement existing grouting equipment owned by the contractor.

Bentonite slurry was prepared in advance and hydrated overnight using a series of portable plastic tote tanks.  Decommissioning operations were accomplished under Peter’s supervision using diaphragm pumps to transfer bentonite slurry to the grouting plant where dry cement was mixed and the resulting cement-bentonite mixture pumped to fill the respective concrete drainage pipes.

The general contractor’s crews successfully completed cement-bentonite work within each pipe at a high rate of production, completely filling each pipe within a few hours.  The cement-bentonite grout produced a stable, thixotropic and cohesive mixture.

Photo Gallery