Recycling of the Shore Pac^® Slurry

After the slurry testing has been completed and the rebar has been placed, a suction line should be dropped just inside the excavation for recycling of the slurry. While the concrete is being tremied it will displace the slurry forcing it upward. A holding tank large enough to hold the volume of slurry contained within the excavation is required to recycle the Shore Pac slurry. When concrete is tremie pumped into the bottom of the hole, the displaced Shore Pac slurry is pumped from the top of the excavation into the holding tank using a centrifugal pump. Disregard concerns about shearing the polymer and destroying it, this is the only pump that will pump a large enough volume to keep-up with the concreted pump truck.

Avoid pumping the last three feet of slurry above the concrete interface, this slurry will be contaminated from contact with the concrete. The impacted slurry looks like oatmeal and only occurs at the contact with the concrete. The last three feet of impacted slurry can be pumped off to a waste tank are allowed to spill over the top can onto the ground to be mixed into the spoil pile by the loader.

The recycled Shore Pac slurry is tested for viscosity and pH. While adding water to restore the original volume additional soda ash is added to adjust the pH. Next the Shore Pac is added to restore the slurry to full strength. Usually it requires about ¼ of the amount of Shore Pac added to the water filling up the holding tank to restore the slurry to its original strength for reuse on the next hole.

When adding fresh dry polymer to recycled fluid directly in the exaction, special care must be taken to assure good dispersion of the polymer grains to avoid forming lumps.  This is because the polymer wets-out and disperses more slowly in thickened fluid than in plain water.  Fanning the recycled fluid across an auger or other object to provide a point of wide and rapid flow facilitates the adding of fresh dry polymer.

Circulation
The polymer slurry shall be circulated from the hole to a holding tank or to the next open hole when pouring concrete.  A centrifugal trash pump will used for this purpose to keep up with the volume of concrete from the concrete pumping truck.   The polymer is circulated within the excavation using the drilling tool.   Recycled slurry will be delivered to the excavation using a double air diaphragm pump (wilden).   Fire hoses will be utilized to pump the slurry from the holding tank to the excavation.

Desanding
The de-sanding operation is eliminated when using polymer slurry, as is necessary with bentonite mineral slurry.  Bentonite slurry suspends sand and polymer slurry does not suspend sand.  During the excavation of the shaft under a head of polymer slurry, all the sand drops to the bottom of the shaft as drilling proceeds

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