Arab Construction World – January 2010
When you picture Sydney, most likely the Sydney Opera House comes to mind. Say “Paris,” and the Eiffel Tower springs up in your mind’s eye. And very soon, when you picture Singapore, the soaring towers of the Marina Bay Sands will define that city. Due to be completed in early 2010, this enormous construction project is pushing the limits of architectural design and construction challenges.
“The unique iconic design of Marina Bay Sands will be a global landmark for Singapore,” says Bradley Stone, president of Global Operations and Construction for Las Vegas Sands Corp, owner of the development. “With this promise comes a challenging engineering and construction process which we continue to successfully overcome.” Las Vegas Sands has invested S$3.85 billion (US$2.77 billion) in the project, not including the cost of the 6 million ft2 (560,000 m2) site itself. The total cost of the development is valued at S$8.0 billion (US$5.8 billion).
When it opens in a few months, Marina Bay Sands will feature three 50-storey hotel towers, crowned by a two-acre Sky Garden bridging across the towers 200 metres in the air. The Sky Garden will offer 360-degree views of the city and the sea. Marina Bay Sands will also provide guests with jogging paths, swimming pools, spas and gardens; an iconic Arts and Sciences Museum on the promontory; one million square feet of integrated waterside promenade and shopping arcade; a one-million square foot convention centre; two 2,000-seat theatres; a casino; and a 4,000 car garage.
Aside from its sheer size, one of the challenges that faced the architects, engineers and construction team was waterproofing. The complex is being built on reclaimed land and surrounded by seawater. Any leaks in the foundations, below-grade areas, or even the acres of roof-top park would be disastrous. The challenge was to find a sole waterproofing product that could address numerous challenges associated with such a mega-project, including all below-grade areas, multiple floors, tunnels, roof tops, lift and sump pits and water tanks.
With the eyes of the construction world watching, it was imperative that proven solutions be found.
The project’s architects, engineers and contractors considered various waterproofing options—traditional membranes, bentonite sheets and several waterproofing admixtures. They narrowed the choice down to only admixtures, ranging in types from densifiers to pore-blockers to crystalline admixtures. But the extensive final evaluation picked the crystalline concrete waterproofing admixture, Krystol Internal Membrane (KIM), produced by Canadian company Kryton International, as the sure solution. The project was awarded to Lee Construction Ltd., the exclusive Kryton distributor for Singapore, in August 2007.
Among the many challenges and requirements were that:
KIM’s integral crystalline waterproofing technology transforms porous concrete into a permanent, water-resistant barrier. KIM is a dry powder composed of Portland cement, fine silica sand and a specific blend of chemicals. When added or applied to concrete, the chemicals facilitate crystal growth, which transforms concrete into a water-resistant barrier. The new, long, narrow crystals block the flow of water by filling the natural pores, capillaries and hairline cracks in concrete. KIM provides a guaranteed defence against water damage and steel reinforcement corrosion. If cracks later form, the incoming water will react with KIM and trigger further crystal growth, filling cracks and keeping the structure watertight.
Due to the size of the project, one single contractor could not have completed the job alone. So the project was divided into “packages” and awarded to nearly a dozen different contractors. What might have been a major logistical challenge was easily overcome, however, as Lee Construction oversaw the addition of KIM admixture at the batching plant as it was added directly into mixer trucks. By simply adding KIM to the concrete mix at the time of batching, waterproofing concrete became a quick and easy process that did not hold up the construction timeline and prevented on-site application errors. About half a million kilos of KIM has been used on the project site.
Using KIM allowed seamless pouring of concrete from one area to the next. There was never a need to wait for backfilling, preparing the substrate or adding manpower to apply a traditional membrane system.
As the project nears completion, more than 60,000 cubic metres of concrete – base slabs, suspended slabs, walls, tunnels and water tanks – have been waterproofed using KIM, exclusively. And in the next few months, Singapore’s skyline will be permanently redefined.