The generally impoverished region around Lesotho's capital, Maseru, has historically suffered from water shortages, a situation which is well on the way to being alleviated by the Metolong Dam and Water Supply Programme (MDWSP). The scheme will improve water delivery to domestic users and the country's textile industry, an important source of employment.
The MDWSP's major structure is the Metolong Dam, an 83 m high roller compacted concrete (RCC) dam with a design crest length of 280 m, constructed on the Phuthiatsana River. Chinese main contractor, Sinohydro, established an on-site batch facility to provide the estimated requirement of 330 000 m³ of RCC and 40 000 m³ of conventional vibrated concrete (CVC). Sinohydro is a global top-ranking construction and hydropower group that is involved in a range of projects on the African continent, and has worked on major international projects such as China's Three Gorges Dam, the world's largest dam.
Sinohydro were interested in using Lafarge South Africa as a supplier since they were a technically sophisticated major company that could supply all of its requirements for cement and fly ash. This was in line with the recently introduced ‘One Lafarge' approach to major infrastructure developments, aimed at ensuring customers receive the optimum all-round benefits from the company's resources. It further reflected Lafarge South Africa's policy of building long-term relationships by delivering true value.
Traditionally, cement for water infrastructure projects has been dominated by CEM I products. Engineers and contractors are cautious about changing established practice, whereas Lafarge SA had phased out CEM I cements and, some years earlier, had developed a complete range of innovative fly ash extended products. The challenge that the company faced was to convince the project team of the merits of its CEM II product.
Lafarge's innovative CEM II
Realising that Heat of Hydration would be a significant concern to Sinohydro, Lafarge SA proposed their premium technical cement, Powercrete Plus CEM II 42,5R. This formulation is a Low Heat cement and also has the capability of being extended further on site with additional fly ash. The engineers and the contractor were not familiar with this versatile, high performance product. It took a two-year determined selling campaign, with strong technical support from Lafarge SA's highly regarded accredited civil engineering testing facility, Quality Department Southern Africa (QDSA), to achieve a change in the technical mindset and the commercial breakthrough. A significant selling point was the same quality and source of fly ash being incorporated in the cement as would be used for on-site concrete batching.
Arising from discussions with the consultants and main contractor Sinohydro, QDSA was requested to conduct laboratory evaluations of the RCC (Roller Compacted Concrete) mix and the CVC (Conventional Vibrated Concrete) mix. The outcome was that based on QDSA's recommendation, Powercrete Plus premium technical cement and DuraPozz® classified siliceous fly ash from Ash Resources' Lethabo facility were used as binder material in both the RCC and the CVC mixes.
Impressive trial results
Trials using the CEM II Powercrete Plus achieved similar results to those obtained during a trial mix programme by the consultants using a type CEM I product. This impressed both the consultants and the contractor, whose previous experience did not include RCC dams constructed using a CEM II cement. A significant factor in favour of Powercrete Plus was that it is a Low Heat Cement with a typical Heat of Hydration value of 227 J/g, compared with the EN 197-1 criterion of < 270 J/g at 41h.
Lafarge's Powercrete Plus has performed exceptionally well, exceeding the contractor's expectations. The consistent quality of the product and its good strength performance has enabled the contractor to systematically reduce the cement content of some of the mixes from the initial design levels.
The use of Ash Resources' classified fly ash, DuraPozz®, has become virtually a standard component of concrete for controlling the heat of hydration in major water retaining structures. This is now especially the case since DuraPozz® complies with the new and more stringent SANS 50450 specification for category ‘S' fly ashes. The consistent high quality product is not only a significant contributor to lower temperatures but the peak temperatures also occur at a later age.
In addition to controlling heat of hydration, incorporating DuraPozz® produces highly effective mix designs that enhance the ultimate strength and durability properties of concrete, while also aiding construction with the improved workability and ‘flowability' of the mixes.
Pride in delivery service
Lafarge South Africa's extensive production facility footprint (five fly ash plants and three cement plants), means that it is in the unique position of being able to guarantee supply of large quantities of consistent high quality cement and fly ash for major projects. In addition, the company's logistics teams have a proud track record for ensuring product is always available on a customer's project site no matter what delivery challenges may be encountered. The contractor is highly complimentary about the delivery performance of Lafarge South Africa:
"We are very pleased that we chose the right cement and fly ash supplier in Lafarge South Africa," comments Mr Xie Yunhua, Deputy Project Manager of Sinohydro. "They not only lived up to their guarantees but they lived up to their reputation for acting as committed supply partners in a project. The company gave us outstanding support, achieving a hundred per cent on-time delivery record to site. If we build other projects in Lesotho or South Africa, we would be happy to have Lafarge as our cement and fly ash supplier."
Safety the No 1 priority
Safety is a non-negotiable Number One priority at Lafarge South Africa and includes contractors working on the company's sites as well as transport contractors. Ash Resources has been supplying the Metolong Dam project for the last two years without a Lost-Time Injury at its Lethabo production plant or to its transport contractors. Similarly, Lafarge Lichtenburg Cement Works, in the North West Province, has supplied Powercrete Plus without a Lost Time Injury on the plant or to its transport contractors.
A supply partner approach
In its building material supply performance for the construction of Metolong Dam, Lafarge South Africa has clearly demonstrated the meaning of the Lafarge Group's brand signature Building better cities. The company's ‘One Lafarge' true partnership approach with the main contractor has technically, commercially and logistically contributed innovative solutions to help the construction of a project rather than merely being a commodity building material supplier.
A technical breakthrough
The longer term impact is that Lafarge has achieved a significant technical breakthrough in the choice of cement for RCC dam construction in Southern Africa. Its innovative CEM II Powercrete Plus cement offers:
The final fly ash usage on project completion at the end of 2014 is expected to be a total of 33 000 tons. Similarly, the anticipated final requirement of Powercrete Plus cement to date is also 33 000 tons. Lafarge South Africa has provided an exemplary technical support and delivery service to Metolong Dam for both cement and classified fly ash that extends the company's proud track record of involvement in Lesotho water projects.
NOTES TO EDITORS
A world leader in building materials, Lafarge employs 64,000 people in 62 countries, and posted sales of €15.2 billion in 2013. As a top-ranking player in its Cement, Aggregates and Concrete businesses, it contributes to the construction of cities around the world, through its innovative solutions providing them with more housing and making them more compact, more durable, more beautiful, and better connected. With the world's leading building materials research facility, Lafarge places innovation at the heart of its priorities in order to contribute to more sustainable construction and to better serve architectural creativity.
In South Africa, the company manufactures and supplies cement, aggregates, readymixed concrete, gypsum plasterboard and interior building fittings. It focuses on providing solutions to help the sustainable development of better cities that benefit the country's people. Through having a strong presence in all of its business lines, it is in a unique position to contribute to urban construction, while also helping to build better cities, rural towns and villages.
Lafarge South Africa also demonstrates active concern for the conservation of the country's wildlife heritage and is a major supporter of the world's first dedicated baby rhino orphanage in Limpopo Province.
Additional information is available on the website at www.lafarge.co.za
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Bridget von Holdt
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