Safe limit of Slag in R83 base concrete and validate the carbonation equation in 3211
B. Mehdizadeh 1*, K. Vessalas 2, A. Castel 6
1 PhD candidate, School of Engineering and Information Technology, University of Technology Sydney 2 A/ Professor, Head of Discipline, Structural and Materials Engineering, University of Technology Sydney6 Professor, Technical Editor of Concrete in Australia, University of Technology Sydney
With the predicted future supply constraints for sourcing good quality fly ash (Class F), the acceptance of highvolume ground granulated blast furnace slag (GGBFS) use in R83 base concrete will increase the utilisation of SCMs in rigid pavement. GGBFS is one of the supplementary cementitious materials (SCMs) considered to be an environmentally friendly solution for the replacement of ordinary Portland cement (OPC) cement in pavement concrete. At the same time, it is also known that increased levels of SCMs in concrete induces carbonation resulting in pavement deterioration over time and a reduction in service life. The research will validate the minimum content of shrinkage limited (SL) OPC content required for the RMS3211 carbonation formulae with the addition of SCMs such as GGBFS and fly ash. The effect of on carbonation behaviour with cement replacement level ranges 15-40% fly ash and 40-70% GGBFS on concrete while keeping the total binder content 350kg/m3 and fixed water-to-binder ratio (0.45) were investigated. Mixes with a lower binder content 250kg/m3 were also evaluated for compressive and flexural strengths, drying shrinkage and accelerated carbonation tests. Accelerated carbonation tests in the lab indicate that increased GGBFS and fly ash content in the concrete mixes will increase the carbonation depth and the carbonation rate which requires validation using field samples of existing pavements. The research project’s primary results will include recommendations to revise the carbonation equation and the total binder content in TfNSW/RMS R3211specification for R83 base concrete.
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