“Achieving completion head of schedule is quite unusual anywhere in the world, but in Vietnam it is quite exceptional”
- George Moir, Engineering Manager of BBBH in Vietnam.
As one of key elements of the new ring road around Hochiminh City, Phu My Bridge has blown a new breeze to the urban life of Hochiminh City since its opening in September 2009. Thanks to it, the transportation for heavy goods vehicles in and out of the city has been eased significantly.
The impressive 705 meter stay-cable bridge has a center span of 380m; the vertical clearance of 45m in a 200m wide zone ensures that river traffic and large vessels can pass under the bridge easily; each pylon is about 140m high and supported by twenty-eight large bored piles of approximately 2.1m in diameter and 75m in length; and the
impressive life span of 100 years.
Such a project demanded for a very strict requirement of quality and construction progress as well as faced a wide range of challenges from raw materials to labour. Despite all difficulties, the main contractor BBBH – a consortium of Bilfinger Berger Civil and Baulderstone Hornibrook – achieved an impressive result: completed the bridge in 30 months, four months ahead of schedule.
After careful analysis and calculation, fly ash blended cement was used. And for mass pour, cement with up to 25% fly ash blended was used in the construction of the bridge. Deck slabs and pylons were built with concrete using cement with fly ash blended at about 15%.
This type of cement displays a good workability and also a very high early concrete strength and durability. Workability and high early concrete strength ensured the contractor would meet the construction deadline as the concrete allowed for a 5 day rotation time to cast the deck segments of the bridge and to move the formwork to its next position. High durability promises a long life for the bridge. The destructive alkali-aggregate reaction that can sometimes be observed with ordinary concrete can be mitigated due to the limited alkali content in such cement and a good choice of aggregates.
The 25% fly ash blended cement which was normally referred to as Low Heat Cement in the market was used to build the 4 massive pile caps that connect the huge pylons to the bored piles. The low heat cement has contributed to the reduction of heat development in the large mass of concrete forming the pile caps, avoiding the risk of cracks that would have endangered the structural integrity of the bridge.
As important as the bridge, the access road to the bridge needed the same attention in terms of durability and technical requirements. To ensure the durability and to maintain a timely progress with the construction schedule,
There had to be strict control on water / cement ratio to achieve high early strength. All details were treated with utmost attention from carefully selecting input materials to applying hightechnology batching to deliver products with desired quality. Three batching plants at Sai Gon South and Cat Lai were strategically planned and mobilized to ensure timely and sufficient supply for the jobsite.
At District 2 tollgate, a concrete pavement was specified instead of the traditional asphalt pavement to avoid the potholes and deformation of the surface due to high traffic density. In order to meet the contractor’s requirements,
Optimised mix design and the fly ash blended cement with low alkali content to reduce the risk of alkali aggregate reaction in the pavement were a good combination, with both complementing each other.
Additionally, to comply with the requirements of the automatic paving machine, the concrete had to be very stable with a low slump. The base layer consisted of cement-bound aggregates to offer a higher bearing capability of the road structure, which means a longer life span of the road with less deformation.
The new Phu My Bridge and his connecting infrastructure contributes not only to the reduction of traffic in Ho Chi Minh center, but is a symbol for innovation and quality as well.
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