First built in 1976, AMP's 49-storey Quay Quarter Tower has become a familiar piece of Sydney's iconic harbour. In 2018, it began a dramatic transformation upgrade to move with the times. This upgrade saw around two-thirds of the existing structure retained and total floorspace nearly doubled in a procedure to blend the old parts of the building with the new.                                                                                      

APozA spoke to Dr Baweja who is Director of Materials at BG&E, Industry Fellow, Civil Engineering at University of Technology, Sydney, and a widely published author of technical papers focused on the durability of fly ash and other concretes. Dak was kind enough to give us an exclusive look into the project's inner workings. "I've been in this industry a long time, and have been working with Supplementary Cementitious Materials longer than most people care to... I've never upgraded or worked on a 50-year-old building before because usually, they're only built to last that long!," Dak said. However, in this special case, client AMP wanted to keep the existing structure and modify it, due to new constraints placed on how high a building may be in modern-day Circular Quay. "A lot of work was done, and we were able to re-use what was there already," Dak continued. 

Supplementary Cementitious Materials (SCMs) like slag and fly ash have been used within the construction industry for several decades, and, in Australia, these materials are reducing embodied carbon rates dramatically. "We found evidence to suggest fly ash and slag was used in the original mix used to construct this building, which significantly adds to the cementitious properties of the cement," Dak said. 

Knowing this, Dak and his team had to do a lot of work to ensure the new mix used was going to be suitable for the existing structure. "50 years ago, they didn't have pumps for the concrete, so they used what's called a kibble and bucket method of application and because of this, we knew there would be variability in the concrete strength... So that lead to us taking up to 4000 cores to test the existing strength of the concrete and come up with a new mix that wasn't going to interrupt the structural integrity of the existing structure," Dak told us. We had a few PhD students from the University of Technology Sydney and Western Sydney University help us with this whole project and they did a fantastic job," he continued. 

Since this was a 50-year-old building, the core of the building was also the same age. This core had to be assessed by BG&E in great detail, to ensure the differential loading of the new mix, wouldn't compromise the structural soundness of the building. "After taking all these tests, we decided to use the SCMs because it adds value to the original cement mix and gave us a more durable product," he said. 

Before wrapping up, Dak made sure to say, "There's still a lot more research that needs to be done when moving into the future with new emerging green products but SCMs have done a great job at increasing the capability of cement mixes and made it possible for old material to be re-used," he said. If anything, this project is a demonstration of the amazing capabilities of our member, BG&E and their ability to execute such projects with materials that are better for our environment. 

APozA would like to thank Dak for his generosity in supplying information to us and his contribution to our member news.