Following routine inspections by Rail and E.M. Highways staff, defective areas of concrete were noted to the walls and soffits. Leaks and condensation within the tunnel over the years had caused the steel reinforcement bars embedded in the concrete to corrode. As the bars corrode they expand causing the surrounding concrete to crack and breakaway. Concerned this could eventually become an issue for trains passing underneath and also compromising the structural integrity of the road bridge above, repair works were instigated.
SWCR Ltd were already the concrete repairs specialists to E.M. Highways under their Highways Agency Area 1 MAC Term Contract (since 2010).
So were instructed to carry out the survey and repair works to the defective areas. Working through the nights (to keep railway open during the day) over a three week period in September, all of the identified defects were tested, broken out, steel reinforcement cleaned and treated, and defects reinstated using polymer modified repair mortars from the BASF EMACO Nanocrete range.