Effects of ground granulated blast furnace slag and pulverized fuel ash on rheology of concrete

The rheology of concrete containing Pulverized Fuel Ash (PFA) and Ground Granulated Blast Furnace Slag (GGBS) has been scarcely studied and reported, despite their increase application as Supplementary Cementitious Materials (SCM) that drives improvement of sustainability of the construction industry. This work studied the effect of these SCMs and Superplasticizer proportions on rheological properties of concrete using rate controlled concrete rheometer. Two groups of mixes containing replacement or addition on mass basis using either PFA or GGBS or their combinations were derived from the control mix. The dynamic yield stress, plastic viscosity and 28 day compressive strength of the control mix are 1258 Pa, 6 PaS, and 40.5 MPa respectively. The results of the rheology tests of the various binary mixes (PFA and Portland cement) and ternary mixes (Portland cement, PFA and GGBS) structural concrete shows wide disparity in the measured rheological parameters. The results show that the decrease in dynamic yield stress of the ternary mix containing 20% GGBS is 4.1%, whereas the decrease in dynamic stress of the ternary mix containing 20% PFA is 35.9% compared to the control ternary mix. The high volume Portland cement replaced ternary concrete can therefore be effectively characterized as a workable and pumpable concrete. Keywords: Rheology, PFA, GGBS, superplasticizer, concrete