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Concrete In Australia : September 2013
28 Concrete in Australia Vol 39 No 3 CONFERENCE TECHNICAL PAPER interpreted as including other materials other than Portland cement. • ASTM C 125--07 specifically defines hydraulic cement concrete. • e new ACI CT--13 Standard on Concrete Terminology produced in January 2013 uses the term "hydraulic cement". Hence, there has been a change in definition from ACI 116R--00. • ACI CT--13 has a specific definition for polymer concrete which uses a polymer resin as the binder rather than hydraulic cement. It is apparent from the above review that the binding phase in standard definitions of concrete is not exclusively Portland cement. Furthermore, supplementary cementitious materials are now widely used in concrete and covered in AS 3582.1, 2 and 3. erefore, this opens opportunities for alternative cements and binders to be considered in the production of concrete and included in existing standards. In addition to the standards considered above, construction projects in Australia may follow state-specific requirements. is is particularly the case for transportation infrastructure. Most Australian state specifications refer to AS 1379 for the definition of concrete and require that cement complies with AS 3972. Only VicRoads Section 703: General Concrete Paving specifically refers to geopolymer concrete and it is understood that changes are currently being made to other VicRoads specifications to permit the use of geopolymers. Further details of the experiences of VicRoads with geopolymer concrete are described by Andrews-Phaedonos (2). If AS 1379 is modified to include geopolymer concrete this will assist in adoption at a state level. Modification of existing state specifications as has been performed by VicRoads would also create a pathway for more widespread use of geopolymer concrete. Specification of concrete for a construction project typically calls for a mix design and/or particular properties. State transportation authority specifications designate mix design limits and required properties for different grades of concrete. Engineers are, therefore, familiar with specifying parameters such as minimum cementitious content, maximum water/ cementitious material ratio and minimum 28 day compressive strength. us, transition to alternative concretes would be facilitated by use of similar and appropriately modified terminology. 2.2 Property requirements Design of plain, reinforced and prestressed concrete in codes and standards such as AS 3600 implicitly assume that the concrete is based on Portland cement. Mechanical and physical properties for conventional concrete are well- established. erefore, adoption of geopolymer concrete for structural applications will necessitate understanding of behaviour and identification of any substantial differences from current design assumptions. Furthermore, durability properties such as chloride diffusion coefficient, carbonation coefficient and sulphate resistance require consideration in order to comply with AS 3600 durability design. 3.0 CURRENT DEVELOPMENTS IN RECOMMENDED PRACTICES AND STANDARDS FOR GEOPOLYMER CONCRETE ere are currently several activities and resources aimed at disseminating practical information and developing standards Organisation/Standard/Document Definition AS 3600--2009 "Concrete Structures", AS 1379--1997 "Specification and Supply of Concrete", AS 5100.5 -- 2004 "Bridge Design Part 5: Concrete" and AS 3735--2001 "Concrete Structures for Retaining Liquids" Mixture of cement, aggregates and water, with or without the addition of chemical admixtures. CCAA/Standards Australia HB 64--2002 "Guide to Concrete Construction" Concrete is a mixture of cement (Portland or blended), water and coarse aggregates (sand and crushed rock or natural gravel), which is plastic when first mixed, but which then sets and hardens into a solid mass. ASTM C 125--07 "Standard Terminology Relating to Concrete and Concrete Aggregates" A composite material that consists essentially of a binding medium within which are embedded particles or fragments of aggregate; in hydraulic-cement concrete the binder is formed from a mixture of hydraulic-cement and water. ACI CT--13 "ACI Concrete Terminology" 2013 Concrete: mixture of hydraulic cement, aggregates, and water, with or without admixtures, fibers, or other cementitious materials. ACI CT--13 "ACI Concrete Terminology" 2013 Polymer concrete: concrete in which an organic polymer serves as the binder. BS EN 206-1:2000 " Concrete -- Part 1: Specification, Performance, Production and Conformance" Material formed by mixing cement, coarse and fine aggregate and water, with or without the incorporation of admixtures or additions, which develops its properties by hydration of the cement. Table 1. Definition of concrete in standards.