RMD Australia supplies formwork and falsework to the Northern Territory’s most expensive road development project to date. The $89 million stage 2 of the Tiger Brennan Drive Extension comprises of a 7.5km dual carriageway linking Palmerston with Darwin and a grade-separated intersection with the Stuart Highway. Once completed it will provide much needed relief to local congestion, reducing traffic delays for about 34,000 commuters per day. As an indication of just how massive this project is, a staggering 120,000 cubic metres of land had to be ‘blasted’ to make way for the new four-lane dual highway extension.
Macmahon Contractors Pty Ltd, the primary contractor to the site, needed a formwork and falsework supplier that not only had experience on projects of a similar scale, but also had the appetite, drive and most importantly the engineering expertise to tackle the challenges that lay ahead.
Securing the contract on this project has been the culmination of 18 months hard work by the team at RMD Australia’s Darwin office. Romano Lazzarin, Branch Manager at RMD Darwin comments, “It’s a great boost for RMD Darwin to be involved in such a high profile project in the region. We wanted to be on this project and the sales team here put in a lot of hard work and perseverance to make sure we were involved, and this paid off in September 2009 when we supplied the first batch of equipment to site”.
RMD Australia’s involvement in the project is quite extensive, including supplying shoring, wall formwork, column and pier supports and falsework and headstock formwork to the projects three 20m wide bridges. But perhaps the most challenging aspect of the build for RMD Australia’s engineers to date was a 52 metre long, 9 metre high, 400mm thick wall that had to be formed in one single pour.
Romano Lazzarin, Branch Manager at RMD Australia explains the potential difficulties in such a pour; “As specified by Macmahon Constructions, this particular wall could have no horizontal cold joints, which meant a single pour of 185m3 concrete. This creates all sorts of difficulties when designing a formwork solution, firstly we had to ensure we could adequately contain that much concrete over such a large area, secondly we had to consider the curing times of the concrete. This is especially vital as with such a publicly visible structure, the final finish of the concrete takes on increased importance. What happens is that when we pour a large volume of concrete the bottom of the pour dries before the rest, then the final finish is compromised.”
Engineers firstly designed the all-important formwork, using Superslim Soldiers as the primary vertical beams and secondary LVL timber beams horizontally with high quality plywood shuttering. Both sides of the wall formwork were then connected with Rapid Bar Ties ready for pouring. To add additional strength throughout the formwork, Superslim props were anchored to the concrete base to accommodate the large volume single pour, and provide additional support near the base of the formwork where the bulk of the load would be most felt.
To avoid a substandard final finish to the concrete the pouring of the 185m3 of concrete had to be calculated to achieve the correct flow rate and avoid any premature hardening of the concrete, especially difficult in the mid summer conditions of northern Australia. To ensure a consistent flow two concrete pumps were operated simultaneously at the pre-calculated flow rates. The result was a resounding success, with the extra strengthening applied to formwork resulting in zero movement and the achievement on an excellent class two finish.
Graham Gust, Project Engineer at Macmahon Contractors Pty Ltd commented, “RMD Australia’s approach to this project has been second to none, from the very beginning they showed a commitment to be part of what we are doing here. We have a selection of hire and sale RMD equipment on the site, backed up by RMD’s engineering staff, all of which is meeting the high standards a build of this size requires.
Stage 2 of the Tiger Brennan Drive Extension is due to complete in mid 2010, we hope to be able to bring you an additional report on the bridge construction later in the year.
