During routine maintenance of the Second Severn Crossing, the 5128m bridge between England and Wales, it was found there were a large number of very small cracks in the concrete blocks which make up the carriageway of the bridge.
These concrete sections are bonded together but, more importantly, they are also pulled together and kept under tension by steel cables running between the concrete anchor blocks.
Koster Aquatecnic’s Injection Expert visited the site and conducted smoke tests which confirmed that the crack networks within each block were interconnected.
It was apparent that drilling boreholes was not possible as the vibration and stress could have been enough to break out a loose island of concrete. Pressurised injection was also ruled out for the same reason. By designing a vacuum injection solution with surface mounted packers we were able to avoid any stressing of the concrete. The process we designed required no drilling and used only extremely low pressure.
After conducting trials on the process under Koster Aquatecnic supervision a core sample was taken which confirmed the cracks were fully filled and the adhesion to the concrete was good.
Following the trials the injection work continued smoothly and from further quality control core tests we have found that even the smallest crack we have found (approx 8 microns) was fully bonded and filled with KB Pox IN.