Sika is relied upon for its innovation and consistency when it comes to maintenance and repair of large structures, so it was not surprising when Aurecon specified various Sika products for the maintenance of the Van Staden’s River Pipe Bridge in Port Elizabeth. Nelson Mandela Metro Municipality retained the services of Contractors Stefanutti Stocks for this project in which the disrepair and damage that had occurred over several years was confronted.

One of the challenges facing the contactors was that the columns that the bridge was resting on were below the water line. This was the area that was in need of attention so, in order to reach these four metres below the waterline, watertight metal casings were constructed (welded) around the concrete columns. Thereafter water was pumped out to enable workers to do the required repairs.

Sika Monotop-612 (280 x 25kg bags) was used as the repair mortar for the concrete columns. This cementitious, polymer modified, low permeability mortar, containing silica fume and synthetic fibre reinforcement, is designed as a high strength repair and reprofiling system for concrete substrates. It is particularly suitable for application on overhead and vertical surfaces using the wet spray method and can also be placed by hand. Sika Monotop-612 offers excellent workability characteristics with an adjustable consistency and superb slump resistance. It also provides good mechanical strength and resistance to water and chloride penetration, and is easily sprayable in layer thickness of up to 30mm.

Bonding used for the Monotop-612 was SikaTop Armatec 110 (40 x 1,75lt kits), a cement-based, epoxy-modified, three component, anticorrosion coating and bonding agent. Sikagard-706W Thixo (3 x 200lt), a silane-based, migrating corrosion inhibitor cream was applied to the old concrete as a water-repellent impregnation (hydrophobic treatment). This is used for absorbent substrates, such as concrete in civil engineering or building concrete structures subjected to heavy stress due to freeze and thaw cycles and de-icing salts, chloride attack in marine environments. Sikagard-706W Thixo offers a non-sag consistency, allowing wastage-free application of sufficient quantities and assuring deep penetration.

Sikagard-550W Elastic was painted over the concrete once repairs were completed. This plasto-elastic protective coating based on UV-curing acrylic dispersion has excellent crack-bridging properties even at temperatures below 0°C; It is used for the protection and enhancement of concrete structures, especially exposed concrete surfaces with a risk of cracking. SikaGrout-212 (120 x 25kg bags), a high performance cementitious grout was used for grouting of bulk repair areas of the bridge. It offers an adjustable consistency, very good flow characteristics, rapid strength development, and high final strengths; it expands by gas generation whilst in the plastic state of curing and is non-corrosive.

With Sika’s advanced performance products used as the antidotes for adverse affects caused by wear and tear and climactic conditions, the Van Staden’s River Pipe Bridge should still be standing in 100 years time.