Mauritius Bridge Job

November 2022

  • Location - A1 Bridge outside Port Louis, Mauritius 
  • Scope of Work - Failure on lift 3 castings of the cable suspension pylon. Honeycombing on the concrete discovered on removal of shutterboards. Engineers specified Hydrodemlition to facilitate removal of concrete, and to recast the entire lift 3 section. Hydrodemolition was specified in order to save the rebar and reduce stress fractures in the existing structure and the lower lifts of the pylon. More importantly the cable sadles cast into the structure needed to be sved and re-used as they are custom made for the bridge. Remanufactureing the sadles was not an option as tis process would take 9 months.
  • Demolition - The area to of demolition was 6m wide x 6 m heigh x 6 m long
  • Accessibility & Height - Remote loaction with limited access. Ground level to top deck was 90m. Water had to be pumped up from the river bed vaia filtration systemint storage tanks on the bridge. The water had to feed 2 x Jetstream 4215 units delivering 240l/min  at 1000 bar. 
  • Rebar Congestion - Rebar cage was extremely congested - Y25 - Y40 rebards. This contributed to the initial concrete failure during pouring. Concrete didnt fully penetrae rebards thereby leaving empty voids. 
  • Noise & Debris - The work area had to be insulated and soundproofed with heavy duty shutterboards with a layer of sound proofing inbetween. This was required to reduce noise levels at created by hydrodemolotion both day and night. Each panel weighed 1.7 tons and was 500mm thick. This also contained the debris from falling off the bridge deck and protected the site office 90m below. A bund wall was created around the perimiter of the bridge deck to contain waste water so it could be routed to a disposal site.
  • The project took 32 days, in 24 hour shifts
  • Equipment was an Aquajet 410 robot and an Aquajet spine.