The sectional pre cast concrete digestate storage tank on our clients anaerobic digestion site had been severely attacked by hydrogen sulphide and biogenic sulphuric acid.
We proposed the repair of the concrete using Natcem concrete repair materials prior to the application of a proven crack bridging tank lining.
Preparing the concrete
Initially all surfaces were prepared by method of water entrained abrasive blasting to remove loose and degraded concrete. Water entrained blasting was selected to minimise the release of free silica which is a respiratory hazard.
Following preparation the eroded concrete was repaired using Natcem repair materials. These were selected as they continue to harden indefinitely, eventually reaching a compressive strength closer to the 60Nm of the original pre cast concrete panels.
Lining the tank
For the tank lining were proposed the application of Remmers Epoxy Universal. We have used this crack bridging epoxy coating to line and reline over 50 anaerobic digestion related tanks. The key benefit of this tank lining material is that as well as excellent chemical resistance, this tank lining material can crack bridge to 0.2mm – the design width of this concrete.
Following testing of the moisture content of the concrete and ensuring the correct climatic conditions for coating application Remmers Epoxy Universal was applied in three coats by method of airless spray, at a practical consumption of 0.4Kg/m2 per coat.
As part of our standard quality assurance the new tank lining was checked for pin holing and where found marked with chalk, prior to touching in using the same material.
A spark test is an essential part of the tank relining process, as a single pin hole is point of failure that will allow aggressive chemicals to attack the concrete beneath.
The works were provided with our standard 10 year warranty, giving the client peace of mind in their investment.