Will you still need me… when I’m sixty-four? A story of ageing bridges

Major rehabilitation projects for severely deteriorated reinforced concrete structures can easily run into the millions of dollars, therefore maintaining a suite of operational infrastructure becomes increasingly difficult when contending with limited budgets. Unfortunately, the deterioration of reinforced concrete is not visible until very late in the deterioration cycle and by then significant works is typically required to repair damages. 

The authors will present three case studies which explore the ability of modern investigation techniques to diagnose the current condition and expected life of a bridge. In each case, a different remedial strategy was selected, always aimed at either preventing/delaying future deterioration or at treating the active deterioration. The case studies focus on bridges ranging from 20-100 years old, constructed using various methods, exposed to different environmental conditions (non-saline river to full marine) and subject to different load requirements (pedestrian to highway traffic). The projects illustrate the benefits of early investigation of concrete structures which enable the prediction of the cause and onset timeframe for future deterioration. Once this information is available, the selection and implementation of suitable preventative maintenance works (such as coatings) can significantly delay more costly repairs. However, even in the cases where corrosion has initiated, mid-stage intervention using targeted corrosion control techniques show the ability to provide long-term life without the cost and disruption of a full-scale rehabilitation. 

A brief overview of available preventative maintenance and rehabilitation techniques, when to use them and their relative cost is also presented.