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Concrete In Australia : June 2012
10 Concrete in Australia Vol 38 No 2 NEWS Superway rises above Adelaide Construction of an elevated freeway in the northern suburbs of Adelaide continues with major concrete works under way. e $842 million South Road Superway project features a 2.8km elevated roadway up to 19m above South Road in Wingfield and Regency Park. e roadway is being constructed by Urban Superway -- a joint venture between John Holland, Macmahon Contractors, and Leed Engineering and Construction. e elevated roadway will feature a dual carriageway with three lanes in each direction. e large concrete structure is designed for car and truck freight and will have a speed limit of 90km/h. e elevated roadway is being constructed using the balanced cantilever segmental construction method, which is considered one of the most efficient methods of building an elevated road without the need for temporary formwork that would disrupt traffic. It will feature 740 piles, 68 pile caps, 68 curved piers, 2201 precast segments and 204 Super-T sections. In the method, construction commences from the permanent piers and proceeds in a balanced manner to mid-span. A final closure joint connects cantilevers from adjacent piers. e structure is therefore self-supporting at all stages. When a segment is lifted into position, adjoining match cast segments are coated with epoxy and temporary post tensioning bars are installed and stressed to attach the segment to the cantilever. Typically, after a new balancing segment is in place on each end of the cantilever, post tensioning tendons are installed and stressed from one segment on one end of the cantilever, to its counterpart on the other. Consequently, as segments are added, more top cantilever tendons are added. e piers are made from concrete poured into formwork and each pier is supported by an average of 8-16 piles. During February, the last pile for the main alignment of the elevated roadway was installed. All 740 continuous flight auger (CFA) piles are 1050mm in diameter and have an average depth of 30m. Each pile features 2.5t of reinforcing steel and 30m3 of 50MPa concrete. Some locations have required the use of additives to protect the piles from acid sulphate soils. e piling started last April and each pile took approximately 1.5h to install. In total 2500t of steel and 3700 truckloads of concrete were used to create the piles. e 68 piers, which are constructed insitu, include an average of 70t of steel in each. ey are up to 13m-high and contain an average of 172m3 of concrete in each. Plasticiser is added to each pier to assist workability and increase strength and durability of the 40MPa structures. e precast segments, which form the carriageway of the elevated roadway, are being manufactured in a purpose built shed adjacent to the road alignment. e joint venture secured land for the casting yard along South Road itself, and the operation is growing towards a workforce of around 220 people, working in shifts to produce around 40 segments a week. More than 350 segments have been completed with more than half of these already erected on completed piers. With an average of 5.5t of reinforcing steel, the precast concrete segments weigh up to 90t and are transported on a large trailer to the heavy duty lifting equipment sitting on the pier segments. e segments are between 13.6m and 19m wide at the top and between 5m A segment of the elevated South Road Superway is attached using the balanced cantilever approach along the route in Adelaide.