THE PROBLEM
Our client required the application of a Waterproofing bandage solution in order to accelerate the programme of works on site as the hydrophilic strip used in the assembly of the pre cast concrete tanks would take too long to swell sufficiently in order to pass the water leakage test.
SOLUTION
As requested by our client we quoted for the application of a waterproofing bandage solution. We selected Master Builders 930/933 bandage system.
How these Waterproofing Bandage systems work is by employing an elastomeric bandage which is adhered only at the perimeters, the joint area beneath is free to move without splitting the bandage. The Waterproofing Bandage can elongate in excess of 400% without splitting, ensuring that fluid tightness is maintained regardless of substrate movement.
When applying these Waterproofing Bandage systems good adhesion is essential as the stretching action imparts a lateral load on the bonded epoxy adhesive. Poor adhesion of this epoxy adhesive as a result of poor preparation would result in the Waterproofing Bandage debonding from the concrete substrate, causing loss of fluid tightness.
Preparing the concrete
To ensure the best possible adhesion the concrete was prepared by method of 500 bar High Pressure Water Jetting. As can be seen in the photos this removed the layer of surface laitance which is present on all new concrete as a result of fines within the material coming to the surface during production of the panels. The benefits of preparation by method of High Pressure Water Jetting are two fold. Firstly the preparation is completely dust free, preventing the exposure of operatives and other personnel to harmful Silica dust during the preparation works. The second benefit is that this method of surface preparation produces very low levels of hand arm vibration when compared to mechanical tools.
Following preparation the tank panel joints were dried using hot air guns prior to the priming for and installation of a polyurethane jointing compound provided by our client. Although not an exposed finish these were still masked to ensure a neat arris detail.
Ensuring the surfaces are dry
The Master Builders Bandage system is extremely moisture and damp tolerant, so the only climatic conditions were that the substrate and ambient temperatures were above 5 degrees centigrade. We ensured that all surfaces were touch dry.
To ensure a neat and tidy finish all areas not to be bonded using the epoxy adhesive which secures the Waterproofing Bandage in place were masked using tapes. The epoxy adhesive was applied using stiff brushes and spatulas and the masking tapes removed before the material was cured.
In total two tanks were treated, both within a tight programme on site.
