Construction World April 2023

ADMIXTURES

ADMIXTURES FOR THE OMARURU BRIDGE, NAMIBIA

When we think of Namibia, most of us will conjure thoughts of hot, dry desert rock, blanketed seasonally by a blast of beautiful flowers. Henties Bay and Swakopmund are two coastal towns that attract a lot of local and international traffic – so their local infrastructure is vital. The Omaruru River bridge was constructed in 1980 and by 1992 comprehensive concrete repairs had to be conducted. Twenty three years later, due to excessive salt ingress and exposure to the harsh corrosive environment, its structural integrity was compromised to the extent that it necessitated a solution.

B etween June and August of 2021, Sika Nambia Country Manager, Andre Visser consulted with contractors, Actual Impact Group cc, on the supply of products to upgrade and rehabilitate the Omaruru River bridge, in Henties Bay, and the rail overpass bridge in Swakopmund, both on the MR44. The project kicked off with major demolition and clearing works conducted by the main contractor. Given the strict project timelines, the 80 km distance apart and the need to run concurrently, time proved to be the major challenge to the successful delivery of both projects. Anyone familiar with the Skeleton Coast and Namib Desert will know that – with any application process – weather will be the major deciding factor of project success. Having to endure dust storms, mist, rain and wind gusts in excess of 60 km/h, our dedicated teams worked around the clock to ensure that the necessary quality and completion targets were achieved. Once the preparation and concrete work – such as piers and abutments - was complete on the sites, Actual Impact Group was appointed to supply and install a wide range of products, and to assist with technical advisory services for the duration.

While both projects had one or two unique repairs, the range of products and their uses were similar. Sika supplied all the specialist construction chemicals and materials (epoxy/ cementitious grouts, wet/dry epoxy, curing agents, shutter release agents). Initial bridge repair work was attained with SikaGrout®-212, an easy to use, single component, high strength, shrinkage compensated cementitious grout; and Sika MonoTop®-412 NFG. On both projects, Sikalastic®-152 was applied to all exposed concrete components, which totalled around 4450m2. Sikalastic®-152 is a 2-part, cementitious, polymer modified, flexible, crack-bridging, fibre-reinforced mortar for waterproofing and concrete protection, and can be applied to various types of construction substrates. The expansion joints on both bridges were sealed with Sikadur-Combiflex® SG system. Both Sikadur®-42 ZA and Sikadur®-43 ZA were used under the bridge bearing pads on both sites. The former is a 3-part, moisture tolerant, multi-purpose epoxy grouting system, and the latter a solvent-free, three-component, repair and filling mortar based on a combination of epoxy resins and

30 CONSTRUCTION WORLD APRIL 2023