CHRYSO Group products for largest rubble masonry concrete dam
The Chryso Southern Africa Group supplied a wide range of products for the construction of the Mndwaka Dam, the highest and largest Rubble Masonry Concrete dam yet constructed in southern Africa.
Mndwaka Dam, which is almost 30 metres high with 30 000 cubic metres volume – is situated in a particularly remote location close to the Hole in the Wall, between Elliotdale and Coffee Bay. The dam’s construction in such an isolated setting called for careful planning in terms of design, construction and materials procurement.
The Mndwaka Dam was entered into two Fulton Awards categories: Infrastructure and Innovation in Concrete. The Fulton Awards are presented every two years by the Concrete Society of Southern Africa (CSSA) for ‘excellence in the use of concrete’ on the African sub-continent.
Both Chryso SA and its subsidiary, a.b.e. Construction Chemicals’ products were used to build the new dam on the Eastern Cape’s Wild Coast. Mndwaka Dam – which provides water for 63 remote rural villages - was awarded a Commendation in the Concrete Society of Southern Africa’s 2017 Fulton Awards.
AfriSam, which supplied the cement and also formulated the concrete mix for the construction of the dam, incorporated CHRYSO Plast Omega 136 water-reducing plasticiser in the mix the cement producer supplied to the main contractor, Zana Manzi Joint Venture. Chryso SA’s Eastern Cape Area Manager, Patrick Flanagan, says the admixture has in the past often successfully been employed in concrete mixes by AfriSam.
The curving lines of the Mndwaka Dam blend into the rolling hills of the Wild Coast.
CHRYSO Plast Omega 136 allows for a significant reduction in the concrete mix without negatively affecting consistency while also increasing the slump/flow of the mix. “Furthermore, it makes concrete more workable, reduces the rate of bleeding, improves cohesion and lowers the viscosity of the concrete mix. By reducing the need to add extra water, the admixture lowers the overall cost and increases durability in an environmentally-friendly manner,” Flanagan stated.
Nick Pike, a.b.e. Construction Chemicals Technical Sales Consultant in East London, says the company supplied the following range of products for the building of the multiple arch-buttress dam:
- brixeal, a bitumen emulsion waterproofing product used to seal concrete surfaces while also acting as a curing agent;
- duragrout, a cement-based grouting compound with graded siliceous aggregates and chemical reagents that prevent shrinkage during curing. “The compound was used for dowel grouting, ferule holes, and repair work,” Pike explained;
- epidermix 344, a structural wet-to-dry adhesive used to bond fresh concrete to existing concrete. The product can also be used to provide a damp-proof barrier within the concrete matrix; * durarep FR, a fibre-reinforced cement-based structural repair mortar that is chloride-free and ready to use; and
- epidermix 318, a general purpose epoxy for the repair of minor defects.
In their submission to the Fulton Awards judges, the contractors, Zana Manzi Joint Venture, stated that the construction of the dam provided abundant employment to residents of the villages surrounding the dam and will be a vital source of water to about 40 000 people living in relative isolation. “The Mndwaka Dam has successfully illustrated the applicability of RMC technology for use in the rural context, and provides a successful precedent for future application in similar circumstances across southern Africa,” the contractors stated in the submission.
“RMC dam construction offers advantages in terms of lower cost but it is the high utilisation of labour, with associated skills development, and the insensitivity to floods during construction that make this particular type of dam so attractive in rural Southern Africa,” the submission added.
Zana Manzi JV built the dam for the Amathole District Municipality. The principal agents were Sontinga Consulting Engineers in association with ARQ Consulting Engineers.