Swansea STW digester tank strengthening
Expansion cracks appeared in the circular concrete tank due to pressure build up in the enclosed digester tank.
Strengthening was required to restore the structural integrity of the tank walls and to reinforce the tank against any future pressure formation in the tank.
An ultra high modulus carbon fibre composite, webertec force carbon sheet was chosen to strengthen the concrete walls to give increased hoop stress capacity. The tank was emptied to remove the live loads from structure and open cracks were injected with epoxy resin. The surface was prepared and two horizontal bands of carbon fibre sheet were applied using webertec force EP primer and webertec force EP bonding adhesive.
Two layers of webertec force carbon sheet were applied to strengthen the tank against lateral forces. The modulus of elasticity of the sheet is 640 kN/mm2 , a tensile strength of 2650 N/ mm2 and an elongation figure of 0.4%. The carbon fibre was supplied in 300 mm wide rolls with a sacrificial backing sheet allowing ease of application to the pre-applied bonding adhesive. The carbon fibre sheet was overcoated with webertec force EP bonding adhesive to fully encapsulate the sheet and protect it from degradation.