Tempo-PCE carried out the required grouting work as well as any additional work requested by the client. All three arches – the north face, the south face, and the lower bridge on the south side of the bridge – were re-pointed with Natural Hydraulic Lime mortar to help contain the injected material and also give additional strength to the structure (whilst allowing the bridge to retain its original flexibility and breathability). Other general maintenance was carried out at the same time. For example, a total of 370 matching reclaimed bricks were replaced.
The three arches were injected at low pressure with a low viscosity cementitious-based grout, a mix of acrylic resin and micro fine cement. The grout helped to bond delaminated and ring-seperated areas together. The total injected material over the three arches was 628.30kg. The total number of holes drilled over the three arches was 1,246 holes, making an average of 0.50kg per hole. The table 6 in the main report (point 4.4) shows the injection points and material quantities injected into each arch.
The structure shows long-term evidence of water ingress. This is due to the bridge being at a local low point, with an official SCC wet spot at the top of Tannery Lane draining down to the bridge. Surrey’s brief was not to waterproof the structure, but instead use the cement-based grout’s hole filling capability as a basic barrier, giving waterproofing as a bi-product. Weep holes were fitted into the structure for the purpose of draining areas that were showing considerable dampness.