Investigation of Half-Joints on Mossband Viaduct

Concrete half-joints on bridges on the trunk road network came into widespread use during the 1960s. Since then the road network has been regularly subjected to the application of de-icing salts to reduce ice formation which has made this form of joint vulnerable to deterioration in the event of cracking of the joint sealant. Such cracks allow de-icing salts to seep through the joint and cause concrete deterioration and corrosion of the reinforcement. This report describes an investigation of a number of sections of half-joint removed from Mossband Viaduct in Cumbria after it had been demolished at the end of 2008 as part of the A74 upgrade scheme. The structure which was constructed using half-joints had been in service for almost 45 years. The half-joints removed from structure were subjected to a careful visual examination and laboratory testing before being broken up to determine the condition of the steel reinforcement. The findings from the investigation were used to make recommendations for updating the advice given in Highways Agency documents on the management of structures containing half-joints.