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Concrete In Australia : March 2012
48 Concrete in Australia Vol 38 No 1 scale production and construction. It is important that performance, durability and batching control issues are resolved. e major impediments include: • Geopolymer mix designs specifically for the higher strength and durability applications to demonstrate compliance with Section 610 requirements. • e confidentiality of the alkaline solution recipes (dosage rates). • e susceptibility of the alkaline solution dosage rates to variation in production batching and subsequent hardened concrete property implications. • e need to demonstrate unquestionable protection of the steel reinforcement and prestressing tendons against corrosion and other forms of potential deterioration. • e need to establish the permeability performance of geopolymer concrete in terms of VPV. In addition, it is very important that much improved practices and procedures, better trained workforce and quality control measures must be utilised in concrete batching plants to ensure the ongoing consistency of production and quality performance of geopolymer concrete. Geopolymer concrete can have a significant susceptibility to uncontrolled water additions at various stages, and excess water additions can have pronounced effects on both the plastic and hardened properties compared to conventional concrete. Lower risk components such as kerbs, edge strips, vehicle and pedestrian crossings, footpaths, median and other concrete surfacings applications which require relatively low strengths of 20 MPa to 32 MPa may eventually become a regular market for geopolymer concrete. Finally, geopolymer concrete has the potential to be used in structural applications for both insitu and precast construction provided the various impediments mentioned above are satisfactorily resolved, although at this stage it may be more suitable for precasting operations where accelerated curing is available, strength development can be assured and only acceptable components may be delivered. As a way forward, the use of geopolymer concrete in lower risk structural applications may be considered on a job by job basis. ACKNOWLEDGEMENTS e author wishes to thank VicRoads for permission to publish this paper. e views expressed in this paper are those of the author and do not necessarily reflect the views of VicRoads. e author also wishes to acknowledge his colleagues Paul Sklepic, Damian Van Dyke and Steve Di Cicco from VicRoads Metropolitan North West Region for their support and contribution, Dr Peter Duxson and David Brice from Zeobond for various communications, and Dr Ahmad Shayan and Dr Aimin Xu from the ARRB Group for undertaking the insitu testing as referenced in this paper. REFERENCES 1. Communication with Zeobond Pty Ltd. 2. VicRoads Standard Specification (2010), "Section 703 -- General Concrete Paving". 3. VicRoads Standard Specification (2009), "Section 610 -- Structural Concrete". 4. Shayan, A and Aimin Xu, ARRB Group Pty Ltd (2010), "Testing Geopolymer Concrete - Retaining Walls at bridge over the Yarra River" Contract Report No. 001959. 5. Shayan, A, "Microstructural examination of geopolymer concrete samples taken from Retaining Walls at bridge over the Yarra River" Contract Report Dec 10.