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Concrete In Australia : September 2008
the sand quantity replaced by E Spheres and Glass Balls to reduce the weight of the canoe. This formed the basis for the design. In an initial meeting, a decision was made on four types of mixes, namely 100% E-Spheres, 50-50% E-Spheres, N30 Sand and 100% Glass Balls, and 50-50% Sloan Sand. These were tested for fl exural strength and weighed for density-mixes. Deciding on the ratio of cement to sand and the other aggregates was quite difficult. Thanks to Ancon Concrete Lab Testing the UniSA team was able to use an Excel program and get a basic idea of the ratio of cement to sand and aggregates to give a strength of 50MPa. Four samples were made of two different kinds of mixes, the difference between the two being the percentage of sand to E- Spheres. With this initial idea UniSA developed three trial mixes varying the amount of cement and spheres and Grace STRUX 90/40. For all these mix designs the team also varied the water content. One of the trials made use of a Grace ADVA Superplasticiser to reduce the amount of water. Minor modifi cations were made to the mixture before the materials were prepared for the pour. Industry support for the UniSA team came from, Ancon Labs, Grace Construction Products, Adelaide Brighton Cement and BASF Construction Chemicals Adelaide University team The 2007/08 Adelaide University concrete canoe team was the first successful team put forward by the university. The team was comprised of ten 2nd and 3rd year civil engineering students. The team was given approximately three months to design and build a lightweight concrete canoe. The Adelaide Uni team built two. This task was to be completed with a budget of $1000 (donated by the Concrete Institute). Several industrial companies also sponsored the Adelaide University team and these included Adelaide Brighton Cement, Sika Australia, Xypex Australia, Bianco Precast, Hanson and Grace Australia. The design of the canoe was broken down into two segments and most of the team members were involved in all The teams in action at the race venue at Mawson Lakes near the Uni of SA campus. aspects of the design. The two segments were design of the concrete mix and the hull design of the canoe. Obtaining a concrete mix that was lightweight was paramount but the mix also had to have enough flexural strength to sustain the applied forces of racing and transporting the canoe. The final mix design was achieved through testing a number of different mixes. To keep the weight to a minimum density, glass beads were used as a primary aggregate. The strength of the fi nal mix was increased by adding reinforcing fi bres and optimising the cement content while maintaining an appropriate density. The hull designs of the canoes were built around the designs of successful canoes keeping in mind the additional constraints brought about by using concrete as a building material. The team looked at the concrete canoe designs from the US championships, as well as commercial designs for standard wooden and plastic canoes. Additionally, the designs of the canoes built by the inaugural concrete canoe teams in 2007 were looked at closely. After the construction of the first canoe was deemed “below par”, the team maximised its chances of success by obtaining much needed help from industry professionals. They included Bianco Precast, which supplied formwork materials; Adelaide Brighton Cement, which provided cement and fly ash and Sika, which introduced some new admixtures and reinforcing materials to the team. The structural design of the second canoe focused predominantly on ensuring the canoe would be stable. A four part male mould was produced out of plywood. The team achieved stability by increasing the width and lowering the centre of gravity and the freeboard of the canoe, but increasing water displacement. The build stage proved to be most problematic as monitoring the thickness of the concrete applied to the mould was diffi cult. Following curing, the mould was removed, revealing the thickness of the concrete to be quite even. The fi nal stage of production was fi nishing and involved coating the canoe with Sika 400N, a heavy duty waterproofi ng paint. The craft was fi nished with the traditional Adelaide red. Conclusion The Concrete Institute’s 2008 Concrete Canoe Challenge was a memorable experience for both teams and the lessons learnt from participating in a group environment – designing, constructing and racing the concrete canoe – is expected to greatly assist in helping to forge future careers as civil engineers. 15