Hydration of mixtures of ‘Ciment Fondu’ aluminous cement and granulated blast furnace slag

Abstract

High alumina cement (HAC) concrete made from a mixture (by mass) of 1:1 Ciment Fondu and granulated blast furnace slag (gbfs) has shown an increasing trend in strength when kept under water over a period of one year at 20°C and 38°C. Over the same period concretes made from neat Ciment Fondu have experienced a sharp fall in strength at 38°C. Work on pastes made from the 1:1 mixture at similar temperatures suggests that its superior performance at the higher temperature when compared to that of neat HAC is due to the formation of C 2ASH 8 in the 1:1 mixture at the expense of C 3AH 6 in the HAC alone. These changes in the hydration chemistry of HAC in the presence of slag lead to a reduction of porosity with time in the hydrated material and its strength increases. Some of the properties relevant to the workability of concrete made from the 1:1 HAC + slag mixture have been determined. The hydration chemistry of the blended cement has been studied at 4°, 20° and 40°C by conduction calorimetry and x-ray diffraction.