Working on the M25 ...
M25 Ship Lane Overbridge (between Junction 2 & 3) carries the M25 motorway over Ship Lane and was constructed in 1977. The superstructure comprises twin adjacent simply supported solid reinforced concrete slabs, measuring 600mm in thickness. The substructure (underpass) comprises reinforced concrete cantilevered abutments on spread foundations at the deck ends.
A ‘special’ investigation carried out by WSP in early 2021 identified leakage through the joint in the middle of the bridge and extensive spalling around joint area. Other areas of spalling/delamination were also found on the soffit and abutments. It was recommended that the longitudinal and expansion joints were replaced; and a full deck waterproofing system be installed to prevent further leakage which was deemed to be the cause of the spalling concrete. Following the replacement of the deck joints and waterproofing, all areas of spalled, delaminated and cracked concrete were then to be removed and repaired as per the Highways specification.
CRL was awarded the contract through Octavius Infrastructure Limited (formerly Osborne Infrastructure) for the works and moved onto site in early May. Due to the underpass having to be closed the works were programmed for 11no. 12 hr shifts to ensure the works would be completed on time.
The repair process consisted of the removal of the defective concrete either side of the soffit expansion joint and abutment walls by hydrodemolition, the installation of CPT Patch Gard galvanic anodes within the patches and the reinstated thereof with Weber DS & RS spray.
Access to the works site was controlled by a 24/7 road closure managed by the principal contractor, with CRL are working throughout the 24/7 shift to achieve the client’s programme. Access to the works face was via scissor lift operated by CRL’s own IPAF trained personnel.
The larger repairs either side of the soffit expansion joint were carried out in phases detailed 1,3 & 5 and then 2,4 & 6 as per the designers’ requirements. The repairs to the abutments were not phased and could be carried out concurrently with the soffit repairs. It was a requirement of the specification that the ribbed feature of the abutment walls was to be maintained within the repair necessitating the use of straight edge timbers to form the ribbed feature within the repair. Test panel cores for sprayed concrete were taken for compressive testing.
"The tight programme and having to work 24/7 was a tough ask, but I am glad to say out Team were up to the task and performed well."
Kevin Hodgson | Senior Contracts Manager | CRL
Contact Us