The technology of unsteady concrete casting comes into being has an advantage that, after executing a preceding cast piece, it is possible to move in execution of a following cast piece without handy removal, and to shorten the time of execution from 15÷20 days to only 5 days. The successful manufacture of carriage for unsteady concrete casting applied to the execution of beams by reinforced prestressed concrete with large span, with concrete beam portion weighing over 130 tons, length of cast piece of 5m and bridge width up to 23.5m. Meanwhile, by traditional technology, the above corresponding figures being only under 50 tons, 3m and 6m.

The unsteady concrete casting technology is particularly effective for projects executed at localities with complicated geographical and hydrological conditions, weak geotechnical features, requiring free passage of boats during the construction of bridges. On the basis of experiences drawn from the execution of Phu Luong bridge (a first ever large span bridge by reinforced prestressed concrete in Vietnam), TEDI had boldly researched for designing, manufacturing, putting into operation specialized carriages, thus substantially contributed to a development trend of advanced technology in Vietnam.

The first product in the successful application of this innovative technology is the Quán Hầu bridge with 3m long, 12m wide, 130 tons heavy cast piece. From this achievement, TEDI engineers continuously improved the design for manufacturing series of such carriages for other large bridges. At Quán Hầu bridge, the carriage moves by wheels on rail; at Bình Phước, Câu Lâu, Tô Châu bridges, the carriage moves by sliding stand to increase stability, to be easy for manufacture, installation and displacement.

The successful manufacture of carriage for unsteady concrete casting has largely reduced expenses of contractors. Previously, for constructing large bridges, contractors had to import unsteady concrete casting technology from France and Switzerland with cost from USD 400.000 to USD 600.000 / set. Meanwhile, large span carriage for unsteady concrete casting from TEDI with equivalent performance costs only 30÷40% as compared to imported one. Reduction of execution expenses means reduction in cost of the works. For instance, the cost for 1 cu. m of Phu Luong Bridge by Swiss technology is about USD 1,600, of Song Gianh bridge by French technology is about USD 1,700 respectively, whilst with TEDI technology, the corresponding figures being only USD 600÷800.

Source: Science & Life, issue n° 74 (1792) page 5, 16/9/2005