Reactivity Alteration of Granulated Blast Furnace Slag by Mechanical Activation for High Volume Usage in Portland Slag Cement

Abstract

Augmenting granulated blast furnace slag (GBFS) content in Portland Slag Cement (PSC) beyond the conventional limit of 70% is the stimulus for this study. Such enhancement other than bringing down the carbon footprint of cement conserves natural resources. However, beyond 70% slag incorporation, early strength gain of PSC is meagre because of its low reactivity. This study explores mechanical activation (MA) of GBFS to alter its reactivity, and thereby raising the possibility of increased slag incorporation in PSC. MA of slag is carried in an eccentric vibration mill. Formulations with different MA slag contents and clinker are studied in terms of heat of hydration (using isothermal conduction calorimetry) and compressive strength (CS). CS of clinker-slag formulations augmented with the extent of MA. Hydration behaviour of these blends i.e. increased heat evolution, accelerated reactions etc. is in agreement with CS values. X-ray diffraction and TG-DTG employed as complimentary tools to comprehend the hydration process corroborate with CS results, and hydration characteristics. Thus, MA can be used to enhance the hydration characteristics (reactivity) of GBFS, and henceforth its content in PSC. Sufficiently activated slag incorporation even up to 90% yields comparable strength than commercial PSC at all ages of curing.