DavidBallGroup

Innovative Product Development for Ancient Bridge Restoration

Spanning the River Ouse in England is a 700 year old, six span, masonry arch bridge. A scheduled Ancient Monument and Grade I listed structure it was constructed from either side of the river by two Local Authorities, each imposing their own distinctive style on their halves.

Nowadays, the bridge carries traffic over the river and has consequently suffered not only natural deterioration, but also the effects of an increasing volume of traffic.

Two of the restoration requirements were the need to keep bridge open to traffic, and to guarantee that all work would satisfy the English Heritage's criteria.

Major defects included cracked, spalled and eroded stonework, missing blockwork, defective pointing, staining, water damage and leaching, together with movement of some of the spandrels.

David Ball Group's technical team modified their Instacem Underwater Mortar to satisfy the demands of this project. They produced a fine, free-flowing grout suitable for above and underwater pointing, which would:

• Displace water
• Seek and fill large and fine fissures
• Be capable of being pumped through 10mm tubing
• Remain cohesive under water
• Have a two hour open time to provide adequate mixing and pumping
• Have a strength similar to existing lime mortar infill material
• Be non-shrink

A rapid-set pointing mortar to match the stone of the bridge once dry satisfied the performance and aesthetic requirements to close the stonework during the grouting operation. A setting time of three minutes enabled rapid pointing times to be achieved and avoided losing grout under water level.