Project: Two sludge tanks and a digester tank, Winnipeg, Manitoba, Canada
Designer: Stantec Windsor, Ontario and Stantec Winnipeg, Manitoba, Canada
Contractor: GC – PCL, Winnipeg, subcontractor Penta Coatings Inc, Winnipeg, Manitoba
Gemite products: Cem-Kote Flex CR, Gem-Plast TC, Cem-Kote Flex Plus and the Reinforcing Fabric HD, Fibre-Patch OV
Objective: the repair, waterproofing, H2S protection of all tanks and also gas-proofing of the digester tank. The deep deterioration, up to ½ in, of the sludge tanks is shown in Figure 1 and the interior of the sludge tank is shown in Figure 2. A high pressure wash, 7,000 psi, was used to remove deteriorated concrete which further increased the depth of deterioration by approximately 1/8-1/4 in. Wall and ceiling surfaces were repaired and leveled off by wet process shotcrete applied Gem-Plast TC. The partially repaired wall of the sludge tank is shown in Figure 3. The digester wall was less severely deteriorated than the sludge tank walls but exhibited severe cracking due to accidental over-pressurizing of the tank especially in the ceiling slab of the tank. Figure 4 shows some large digester tank wall cracks that were epoxy injected but surface preparation had exposed a larger number of cracks and it would have been too expensive to inject all the cracks. Therefore the following repair procedure
The top (bottom?) 12 feet of the wall was first repaired by spraying and trowel application of Gem-Plast TC to achieve a smooth surface as well as to cover deep vertical form depressions. Note: proper application of the Reinforcing Fabric HD requires a smooth and even surface. After high pressure water cleaning of the Gem-Plast TC, the top 12 feet of the tank wall was treated with a layer of Cem-Kote Flex Plus, reinforced with the Reinforcing Fabric HD. In the area below that level all the remaining cracks which had not been epoxy injected were coated with a layer of Cem-Kote Flex Plus – but only over the cracks.