A STANDARD grade of cement is being used in the construction of the Ngqura Harbour at Coega for the first time ever in a marine project. Extensive research and development carried out by supplier PPC Cement between 2000 and 2002 showed that its all purpose cement, SureBuild, would be the ideal product to meet most of the required specifications for the concrete to be used at the Ngqura Harbour. “As the newest commercial port in South Africa, it is essential that the Ngqura Port can withstand the test of time and hence the selection of appropriate construction materials was essential,” said David Brown of the National Ports Authority. “This is groundbreaking research for the construction industry and will result in significant cost savings for the project. It was essential that we were able to provide the necessary proof and data to prove the capability of SureBuild, hence the three-year research project undertaken by the PPC Cement team. We are confident that it will prove its durability, reliability and performance on this project,” said John Blackbeard, chief operating officer of PPC. PPC Cement will be supplying 240 000 tons of SureBuild to the Harbour Project over the next three years. This cement will be used for the concrete structures at the three main quay walls and the 26 500 dolosse which will be placed at the breakwaters. In total, 770 000m3 of concrete will be used in the construction of the Ngqura Harbour. In the reinforced concrete structures, fly ash, an extender, will be added to the SureBuild, however, in the un-reinforced structures, 100 per cent SureBuild will be used. In the reinforced structures, a 25MPa is required with a 38mm aggregate or a 40MPa with the 19mm aggregate. In the un-reinforced structures, 35MPa is required with a 38mm aggregate for the breakwater cappings and 25Mpa is required with a 38mm stone aggregate for the quay wall sub structure. Excavation work for the three quay walls is well underway, running 24 hours per day, seven days per week. At present the contractors are moving in the region of 50 000m3 of material per day. In total, the NHC will move 40 million m3 of sand and 7,5 million tons of aggregate during the construction of the Harbour. In the case of the dolosse, an early strength capability of 5MPa is required in eight to ten hours for stripping and 2MPa flexural strength is required within 16 hours so that these massive structures can be lifted. During the cooler winter conditions with lower ambient temperatures, a blend of 50 per cent Surebuild and 50 per cent OPC has to be used to achieve hydration rates yielding the abovementioned stripping and lifting requirements. A kerosene fired water heater has also been installed to supply 60 degree water to heat the aggregates which will also increase the early strength of the concrete. To produce one 30 tonne dolos, 4,3 tons of cement is used and this translates into 12,5m3 of concrete. The NHC is running a 24-hour operation at the Dolos Yard in order to achieve the objective to produce between 44 and 52 dolosse per day using a two-shift rotational process. Once the dolosse have reached the 40 MPa strength within 28 days, they will be placed at the breakwaters. They are placed using a crane with an on-board GPS system, which has an accuracy of 2cm. It is envisaged that one dolos will be placed every seven to ten minutes. “The supply of cement to a project of this nature is vital. Timing and reliability is essential as we will be producing 70 000m3 of concrete per month over the six month peak period and it is critical that we can rely on our cement suppliers to ensure that the concrete batch plants do not suffer any unnecessary delays,” said Rolf Klockow, Site Manager for Ngqura Harbour Contractors. The cement being supplied to the contractors is produced at PPC Cement’s Port Elizabeth’s factory, which is running at full capacity to meet the demand for the Ngqura Harbour Project. In order to meet all its Eastern Cape customers’ needs, PPC Cement will be sourcing a total of 100 000 tons of bagged SureBuild over the next three years from its Slurry factory in the North West Province. Two Affirmable Business Enterprises (ABE’s) - Nyusani Investment (Pty) Ltd and Mkhuseli Cement Distributors will be distributing PPC Cement’s product to the construction site. PPC Cement has worked with these two Port Elizabeth-based companies in the past and has undertaken to support them in any way possible to ensure efficient and cost effective cement supply to the Project. “The development of the Coega Industrial Development Zone is a wonderful milestone in the Eastern Cape’s history, and it is an honour for PPC Cement to be associated with yet another project of this magnitude,” concluded Blackbeard.