Hackwood Road Bridge M3

THE PROJECT

The M3 Hackwood Road Bridge is located near Basingstoke on the M3 motorway. It required extensive concrete repair over large areas, due to water ingress causing the corrosion of the steel reinforcement through carbonation and chloride attack. The repairs were undertaken as part of the Scheme Delivery Framework (SDF) for National Highways. Continuity and half-cell tests carried out revealed weak areas within the bridge’s rebar.

THE SOLUTION

Sacrificial anodes were installed to the perimeter of all repair areas prior to Renderoc DS being used to spray back replacement material. Renderoc was selected as the best product solution due to its low rebound performance, which is well-known and tested in the market, having been used in many similar applications. Renderoc DS is fully compatible with all anode systems due to its low resistivity. This is true for a majority of the Renderoc range, meaning it can be use alongside cathodic protection. Renderoc HB45 hand applied mortar was also used where access was limited. Each phase of the repairs lasted approximately 2 weeks, involving breakout, continuity tests, anode installation, area preparation, spraying, and a 3 day curing period before moving onto the next section.

THE BENEFITS

The corrosion and potential spalling of the existing concrete meant that there was a risk to health and safety of the bridge. If left unrepaired this could have also affected the capacity of the asset on a major UK motorway. The application process for each section of the repairs was significantly faster due to the spray application method and ensured a comprehensive restoration of the entire structure. Volker Laser completed all works on time and to program.