The aim of the study was to evaluate the performance of high performance concrete (HPC) containing supplementary cementitious materials in both binary and ternary systems. Concretes were prepared to have a slump value between 60-90 mm at a constant water binder ratio of 0.30.Thetest variables included the type and the amount supplementary cementitious materials (SCMs) such as Silica fume, class F fly ash (FA) and Ground granulated blast furnace slag (GGBS). Portland cement was replaced with fly ash up to 40%, silica fume up to 15% and GGBS up to a level of 70%. The physical properties were assessed from compressive strength and transport properties (air permeability and sorptivity), whilst the durability characteristics were investigated in terms of carbonation, chloride migration, chloride diffusion, electrical resistivity and salt scaling resistance. The hydration properties of cement pastes containing SCMs have been investigated in order to understand the behavior of HPC. For Hydration properties, cement pastes were prepared in two series (A and B). Mixes of series A had a fixed water binder ratio of 0.30 with super plasticizer, whereas the water binder ratios of series B were equivalent to the standard consistencies. The results confirmed that silica fume performed better than other SCMs for strength development and bulk resistivity. In terms of resistivity of concrete, the best performance was obtained for 15% SF concrete. When 7.5% SF was used in 40% FA and 50% GGBS concrete, the resistivity was less 15% SF concrete. The ternary mixes containing GGBS/FA and SF performed best amongst all mixes to resist chloride diffusion. The mix containing fly ash showed favourable permeation results. All ternary combinations can be considered to have resulted in high performance concretes with excellent durable properties. The maximum carbonation depth observed for concrete containing 40% FA and 7.5% SF was about 5 mm, which is less than the cover of reinforced steel bars to cause corrosion. The non steady state [2] migration coefficients of concretes containing different types of SCMs were significantly lower than the controlled concretes. The coefficient was minimum for concrete containing 15% SF. The scaled mass for 40% FA concrete was the maximum among all mixes. For concrete containing was maximum among all the mixes. For concretes containing GGBS, there was no significant change in scaled mass, when compared to control concretes. However, the use of 15% SF was found to reduce the scaled mass. The use of 7.5 % SF in 40% FA and 50% GGBS concrete was found to reduce the scaled mass. The x-ray diffraction data showed that with the addition of high volume FA, GGBS and SF the peak intensity of Ca(OH)2 was retarded and quartz peaks appeared in the paste containing FA denoting a certain amount of crystalline silica in FA. This was more pronounced at later age. The combination of 40% FA and 7.5% SF showed the highest consumption of Ca(OH)2. Thermo gravi-metry data confirms the addition of SCMs in cement resulted in the formation of decreased amount of Ca(OH)2 in the hydration products considerably at later age when compared to early age. Although the addition of high volumes of SCMs decreased the compressive strength of cement pastes at early age, the use of 15% SF improved the strength. However from the cost point of view, it is suggested that a combination of 40% FA and 7.5% SF or 50% GGBS and 7.5% SF can be beneficially used to improve the hydration properties and compressive strength of cement pastes.
GGBS, FA, Silica Fume, HPC
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