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Concrete In Australia : December 2014
Concrete in Australia Vol 40 No 4 25 Lowest life cycle maintenance cost on deteriorating structures is likely to be achieved using modern low cost cathodic protection systems. Cathodic protection can eliminate undue noise, reduce costs and increase reliability of concrete repairs. Providing the widest range of CP systems, SRCP also provides expert advice and offer a range of solutions. Call Frank Papworth at SRCP today to discuss your next project on 0411 018 702 or email firstname.lastname@example.org. Why the durAnode system is just one of a dozen anode systems you should know about. srcp.com.au Specialist Repairs & Construction Products which is highly disordered. This time, we came up with a comprehensive framework to decode it, a kind of genome for cement,” Shahsavari said. “In a nutshell, we tried to decode the phases of C-S -H across different chemistries, thereby improving the mechanical properties of concrete in a material way.” One of the defect attributes analysed was in the ratio of calcium to silicon, the basic elements of concrete. Another looked at the topology of atomic-level structures, particularly the location of defects and the bonds between “medium- range” calcium and oxygen or silicon and oxygen atoms – that is, atoms that aren’t directly connected but still influence each other. The team looked at defects in about 150 mixtures of C-S -H to see how the molecules lined up and how their regimentation or randomness affected the product’s strength and ductility. The ratio of calcium to silicon is critical, according to Shahsavari. “For strength, a lower calcium content is ideal. You get the same strength with less material, and because calcium is associated with the energy-intensive components of concrete, you use less rebar and you save energy in transporting the raw material. Also, it’s more environmentally friendly because you put less carbon dioxide into the atmosphere,” he said. Alternatively, a higher ratio of calcium provides more fracture toughness, which may be better for buildings and bridges that need “to give “due to wind and other natural forces like earthquakes. This also applies to well cement subjected to downhole pressure or temperature variation. Shahsavari said it was the first time the team had been able to see new degrees of freedom in the formation of concrete based on the molecular topology. “We learned that at any given calcium/silicon ratio, there may be 10 to 20 different molecular shapes, and each has a distinct mechanical property,” he said. This will open up more opportunities for researchers to optimise concrete from the molecular level up, according to Shahsavari, but only for certain applications. There had been a lot of work in metals and semiconductors, but understanding how defects work in cement was far from obvious, he said. Shahsavari declared it is “perhaps one of the most important discoveries in cement science this century”. One of the most important discoveries in cement science this century. 24-25 - News.indd 25 24-25 - News.indd 25 21/10/14 12:20 PM 21/10/14 12:20 PM