Nguyen Xuan Thao, Site Engineer, Fuvi International, tells us about the unique plastic slipforming system that is being used to construct one of Vietnam’s tallest buildings, the twin Saigon M&C Towers. An innovative plastic slipforming system is being used for one of the tallest building projects, the twin Saigon M&C Towers in Ho Chi Minh City. The system has been developed by the Vietnamese company Fuvi Mechanical Technology Company and is both environment-friendly and cost effective. This development is a part of Fuvi’s programme to develop innovative industrial and construction products using injection moulds for plastic products, die pressing machinery for pressed products and welding robots for fabricated steel products. The process For the project, Fuvi has designed, manufactured and is operating two independent Fuvi slipform units incorporating EH plastic form faces, one on each of the two tower’s cores. The company has appointed Fuvi International as its service contractor for slipforming. The contractor is using about 270 cu m of concrete of grade 750 MPa per eight-hour cycle for the core’s construction. This concrete is daily trucked to the site and pumped into place with the help of a placing boom. The contractor is achieving an average five-day cycle to complete one storey on each of the towers. Advantage over traditional systems Plastic slipforming offers manifold benefits. First, the system does not necessitate the exchange of plastic form-face for high-rise buildings as against wood or metal form-faces that require changing every 10-20 floors respectively. Second, the system is faster and requires less maintenance after each slipping compared to metallic panels. It can be easily prepared for the next slipping and only requires pressure spray water to clean the form-face. For high-rises this is particularly effective as it accelerates the speed of the construction. Third, in plastic slipforming, the plastic does not adhere to the concrete and releases itself when curing is complete, thus saving a lot of the contractor’s time. The plastic panels are lighter than any other slipform panelling, weighing 7kg/sq m as opposed to an approximate 10 kg/sq m for wood, 20 kg/sq m for aluminium, and 31 kg/sq m for metal. They are made from high quality HDPE plastic, which is completely non-toxic. The use of plastic formwork also leads to a very clean site as the contractor does not need to throw away plywood waste. Every material faces the risk of breakage owing to heavy load. But Fuvi plastic formwork uses high safety factors to prevent the panels from breaking. The formwork has been proved to be safe for slab, table, flying, beam, column, wall, gang and jump forms. Moreover, it can be applied to very large walls as well as hydroelectric concrete dams. Cost-effectiveness The use of plastic forming panels is more cost-effective than plywood as wood can be used only a maximum of three months in concrete, but Fuvi plastic panels can be used up to two years without any deterioration in quality. The price of Fuvi plastic formwork for 1 sq m of concrete surface is also cheaper than those for plywood and steel. Clearly a case where the price is right—and so is the product! The technique Slipforming is a building technique that involves the use of forms that are 'slipped' progressively as the structure grows longer, with finished moulded material coming out of the bottom of the form, while new material for moulding is poured into the top of the form. This technique has been used to build very large structures since the 1950s, and some of the world's most ambitious building projects have been accomplished in part with the assistance of slipforming. The project Sited in the heart of Ho Chi Minh City's commercial centre, the twin M&C Towers are valued at about $ 200 million and comprise one residential and one commercial tower with 45 floors each. There is a five-level basement with car park, a five-storey shopping centre, and a helipad on the roof. The towers are scheduled to be completed in the first half of 2011.