Articles

UHPC Used to Repair Bridge Pylons after Delayed Ettringite Formation

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Abstract

The Bourgogne bridge crosses the Saône river in France since 1992. The deck is supported by cable stays and two lyre shape pylons. Only 6 years after commissioning, an important number of cracks appeared on both pylon bases (dimensions 7,65-yard x 2,18-yard x 13,38-yard). After several years of investigations, it was concluded the pathology was linked to a Delayed Ettringite Formation (DEF) which only affected the pylons' bases. The expansion of the pylons' bases was monitored for 15 years until the experts agreed that there was no further evolution. Three solutions have been designed to repair the pylons' bases: cracks injection and carbon fiber strengthening, PT strengthening with reinforced concrete protection and finally a 3,94-in thick reinforced UHPC shell. The UHPC solution has been selected to ensure a waterproofing effect and long-term protection of the existing rebars. The choice was made to cast in place the UHPC to enhance the pylon's base capacity. The first challenge was to produce the UHPC near to the pylons without impacting the road traffic on the bridge: a dedicated floating platform has been developed to facilitate the production. Secondly, specific care was taken to the "flow" criteria of the UHPC formula to ensure a good steel coating despite the high density of steel fibers. The third challenge was linked to complex pouring operations due to the reduced space inside the cofferdam, the small concrete cover and the required specific construction joint geometry to prevent water ingress.

Keywords: bridge, waterproofing, DEF

How to Cite:

Odin, J., Frécon, J. & Flaus, A., (2023) “UHPC Used to Repair Bridge Pylons after Delayed Ettringite Formation”, International Interactive Symposium on Ultra-High Performance Concrete 3(1): 14. doi: https://doi.org/10.21838/uhpc.16645

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