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Concrete In Australia : March 2012
Concrete in Australia Vol 38 No 1 41 a reduction in CO2 emissions of the order of 15-30% per m3 of concrete used. See Figure 1. 4.0 USE OF GEOPOLYMER CONCRETE BY VICROADS In order to obtain a greater understanding of the practical potential of geopolymer concrete, VicRoads has undertaken a small number of trials over the past two years which include the insitu construction of two landscape retaining walls at a bridge over the Yarra River and precast footway panels on a bridge over a freeway and construction of a significant length of footpath (Figure 2). e key requirement with these trials was the need to ensure compliance with the requirements of Section 610 for both the insitu and precast structural concrete components and Section 703 for the footpath work. As such, the mix designs used were based on comparable minimum strength and minimum cementitious content to cement based mixes as allowed in the VicRoads specification Section 610. e insitu landscape retaining walls were characterised by a mix with 40 MPa and minimum cementitious content of 400 kg and the precast footway panels with 55 MPa and minimum cementitious content of 470 kg. 4.1 Geopolymer precast footway panels e choice of a minimum strength of 55 MPa for the precast footway panels was to compensate for lack of sufficient cover to the underside of the units. is was supplemented with galvanised steel reinforcement. A single test unit was manufactured prior to full production to facilitate a better understanding of handling, placing, compacting, finishing, curing and sampling and testing of this type of concrete. e unit was manufactured successfully with only some minor finishing problems which were subsequently improved. e full scale production and installation of some 180 units was completed within an eight week period which is very comparable with conventional type concrete. All units were manufactured within a five week period. e stacking, storage and curing of units is shown in Figure 3. e minimum required lifting strength for the units was readily achieved and the units were cured using polyethylene sheeting. e dark green colour which is a characteristic of the use of slag Figure 1. Jacana Tunnel and Whitten Bridge (Western Ring Road) constructed with significant amounts of SCMs. Figure 2. Geopolymer concrete, retaining wall (l), footway panels (c) and footpath (r). Figure 3. Storage/curing of precast geopolymer footway panels and geopolymer concrete cores with distinctive green colour.