| PROJECTS |
Operational reservoir Based on the original diagnostic survey, rehabilitation proposals and the subsequent product trials, a tailored solution from speciality chemical company Sika was evaluated and chosen to perform the repairs. Umgeni Water appointed Royal HaskoningDHV to take on this rehabilitation project as the project engineer and Sika products were specified on the tender. Smart Civils Construction was the specialised civil contractor. As the work was being done in an operational reservoir, the product choice was paramount to health and safety in ensuring they posed no risk of water contamination. The project’s other challenges were identifying alternative methods of gaining access to the roof structure and shortening the repair time. Smart Civils developed an inventive idea where access to the roof was provided by a design innovation. This involved erecting 550 tonnes of scaffolding, in a bird-cage configuration, from the floor to just under the soffit. The scaffolding would give the contractor access to one-quarter of the roof at any given time, before being dismantled and re-erected as the works progressed. Sika solutions To fulf il the intended task, a decision was made to use SikaTop Armatec-110 EpoCem as the primary rebar protective coating for the concrete repair to protect the reinforcing of steel and inhibit corrosion. Due to the dif f icult conditions, Sika MonoTop-610 was used as a primer to the concrete substrate. The decision to use Sika MonoTop-412 NFG as a repair mortar was because of its unique properties as an excellent wet spray mortar. This application method improved the compaction of repair mortar and increased the application rate of the product. Sika MonoTop-412 NFG also differentiates itself as a single-component, polymer-modified, fibre-reinforced, low-shrinkage structural repair mortar with Sika FerroGard-903 Plus corrosion inhibitor. That is a threein-one solution which delays the start of corrosion and reduces the corrosion rate when it occurs. It also increases the service (Left and right): Rehabilitation of the 350ML Durban Heights Reservoir 3.
“The micro-climate, with wet-dry cycles, creates a favourable environment for contaminants to be absorbed into the reinforced concrete panels.”
life of a reinforced concrete structure. Sika’s carbon fibre fabric impregnated with a structural epoxy resin, SikaWrap-230C, was used due to the age of the structure and minimal concrete cover. Sika Injection-307 was used for refilling the ducts. Sika Injection-307 is a low-viscosity elastic polyacrylic injection resin that can be adjusted to set at a pre-determined time, forming a passivating permanently elastic matrix. Protective coatings Two protective coating systems were appl ied to t he pa nels, na mely Si k a FerroGard-903 Plus, which is a corrosion inhibitor that penetrates down to rebar level over time and forms a protective
monomolecular layer on the surface of the reinforcing steel. The final protective coating in the solution was Sikagard-705 L, a singlecomponent, low-viscosity, solvent-free and reactive impregnation product for concrete and cementitious substrates based on silane. Its unique properties allow moisture vapour to escape from the concrete panels, ensuring they stay dry and thus preventing further ingress of contaminants. Other Sika systems used on site were Sika Primer-3 N and Sikaf lex PRO-3 i-cure, a single-part, moisture-curing elastic joint sealant with high mechanical resistance used to seal the expansion joints of the soffit. Sikadur-43 ZA is a solventfree, three-component repair and filling mortar used to do roof repairs next to the cable ducts. Smart Civils generated 100 local jobs for the duration of 14 months in the Reservoir Hills community. The use of exceptionally durable and high-performing Sika products in the refurbishment of this reservoir will lessen the future refurbishment cycles, saving on material consumption and time throughout the structure’s lifespan.
PRECAST | ISSUE ONE | 2021
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