Volume 16, Number 3, September 2011
Highway bridges often show premature signs of distress such as cracking of the concrete and corrosion of the reinforcement. This can impair structural performance and shorten service life. A new approach to bridge construction holds promise to mitigate these problems and improve performance, compared to normal design practice.
The concept is to employ pre-cast/pre-stressed girders made of ultra high performance concrete (UHPC) and a reinforced concrete slab made of low-shrinkage high performance concrete (HPC). Such a design approach could keep maintenance interventions at a minimum and reduce life cycle costs.
The use of nano-engineered UHPC could enable cost-effective bridge designs with fewer girders that have a smaller cross section and/or a longer span. This means smaller volumes of concrete would be used, thus reducing the superstructure dead load significantly. For deck construction, the use of a self-curing HPC recently developed by the NRC Institute for Research in Construction (NRC-IRC), with low-shrinkage and low-chloride permeability, could prevent cracking and delay reinforcement corrosion significantly.
NRC-IRC is seeking partners for a new project with the main objective to develop a simplified structural and durability design approach for this type of UHPC/HPC bridge superstructure. The approach would be consistent with the Canadian Highway Bridge Design Code and existing pre-cast/pre-stressed concrete technology.
The project may extend to building a demonstration UHPC/HPC slab-on-girder highway bridge. Its performance would be measured using long-term remote monitoring. Service life and life cycle cost predictions using advanced probabilistic analyses will be conducted as well.
Preliminary predictions indicate that the service life of bridge decks could be extended by a factor of four, and associated life cycle costs reduced by a factor of three, compared to decks made with conventional normal strength concrete. This would constitute a significant contribution to sustainability in bridge technology.