by clicking the arrows at the side of the page, or by using the toolbar.
by clicking anywhere on the page.
by dragging the page around when zoomed in.
by clicking anywhere on the page when zoomed in.
web sites or send emails by clicking on hyperlinks.
Email this page to a friend
Search this issue
Index - jump to page or section
Archive - view past issues
Concrete In Australia : December 2011
34 Concrete in Australia Vol 37 No 4 FEATURE: CASE STUDIES after 250 years and to apply a barrier coating if necessary. e treatment for the substructure of the northern approach was to isolate the concrete from potentially aggressive soil or groundwater, by epoxy coating of driven piles to a certain depth and removing and replacing soil adjacent to the pilecaps. To provide a further option for future durability enhancement, the substructure reinforcement cages have been made electrically continuous with access terminals to permit monitoring of electric potentials and fitting of a cathodic protection system. Durability always depends on quality of workmanship. LAJV undertook an education campaign for the workforce to make them well aware of the special 300 year design life and to reinforce the importance of cover, compaction, and curing. 8.0 CONCLUSIONS e New Gateway Bridge is a major concrete box girder bridge with a 300 year design life. Understanding the influence of concrete material properties was fundamental to the design and construction of the bridge to realise its long life. A number of different concrete mixes were adopted to address the different exposure conditions of the bridge elements and also to suit the construction methods adopted and the physical size of the bridge. e properties of the different concrete mixes were investigated to provide input to design parameters like creep, shrinkage and thermal performance that matched the scale of the bridge plus the deterioration parameters like chloride diffusion and carbonation coefficients that dictate the long term performance of the built structure. To achieve a long life the quality of the construction is paramount. e knowledge of the concrete parameters also provided the basis for the planning of construction to achieve casting and stressing cycles that allowed the bridge to be completed 6 months ahead of schedule. ACKNOWLEDGEMENTS e authors wish to thank Queensland Motorways, Leighton Abigroup Joint Venture, and AECOM SMEC Joint Venture for permission to publish this paper. Nevertheless, the views expressed are those of the authors and do not necessarily represent those of the entities. REFERENCES 1. Connal, J, Wheeler, K, Pau, A, and Mihov, M. Design of the Main Spans, Second Gateway Bridge, Brisbane. Proceedings, Austroads Bridges Conference, Auckland, 2009. 2. Hart, J, Muccillo, J, and Connal, J. Design of the Approach Spans to Second Gateway Bridge, Brisbane. Proceedings, Austroads Bridges Conference, Auckland, 2009. 3. Parkinson, C, Taplin, G, and Connal, J ermal Movements of the Existing Gateway Bridge. Proceedings, Austroads Bridges Conference, Auckland, 2009. 4. Zhou, S, Edwards, C, and Connal, J. Modelling of Early-Age Temperatures and an Air-Cooling Pipe System for ermal Control of Massive Concrete Pile Caps for the New Gateway Bridge, Brisbane. Concrete Solutions Conference, 2009. 5. CIRIA. C660, Early age thermal crack control in concrete, 2007. 6. Connal, J and Berndt, M. Sustainable Bridges -- 300 Year Design Life for Second Gateway Bridge. Proceedings, Austroads Bridges Conference, 2009. 7. Standards Australia. AS 5100-2004 -- Bridge Design. Figure 8. Predicted carbonation rates. Carbonation Rate = 3.0 mm/yr 0.5, S50 25% Fly Ash 0 50 100 150 200 250 300 Time (years) 80 70 60 50 40 30 20 10 0 55 mm Depth of Carbonation (mm)