THE PROBLEM
The anaerobic digestion plants Digestate storage tank was leaking. This was a result of the unusual slab make up where one slab had been poured on top of the original cracked slab. Digestate was leaking between the sectional tank walls and the slab and entering the leak detection system.
SOLUTION – POLUREA, SPRAY APPLIED
We proposed the application of a seamless polyurea spray applied tanking/lining system to seal the slab. However careful consideration had to be given to the specification as the client did not want the existing glass enamel abrasive blasted due to the risk of damaging the surrounding panels of the sectional tank.
Preparing the tank floor using high pressure water jetting
Initially the tank floor was prepared by method of high pressure water jetting to remove softened concrete. The walls were also prepared by method of high pressure water jetting.
Once prepared and waste wash water pumped out the glass enamel tank panels were treated using an acid treatment to expose fresh silica in order to ensure excellent adhesion of the subsequent polyurea spray applied tank lining.
To lessen the profile of the badly eroded tank floor and epoxy scratch coat was applied by trowel using a damp tolerant epoxy primer mixed 1:1 with kin dried quartz.
A second primer coat of damp tolerant epoxy primer was then applied to the concrete tank base to ensure it was fully sealed prior to the application of the polyurea lining.
A mastic fillet was installed at the tank wall/floor interface to isolate this potential point of movement from the polyurea lining.
Spraying the Poluyrea
SPI HT100F UB pure polyurea was spray applied to a thickness of 2mm with the inclusion of their AE4 adhesion promoter. This additive acts as a bonding bridge allowing the polyurea to bond to the free silica in the glass enamel substrate.
The tank lining was tested for pin holing using a DC holiday spark tester and any defects touched in using the same material and application equipment.
Finally the top edge of the lining was protected using a polyurethane jointing compound.
