Effect of fine mineral additions on granular packing of cement mixtures

Abstract

This article concerns the influence of the physical characteristics of 18 fine mineral additions on water requirement, agglomeration and packing density of pastes. The main objective is to determine the principal parameters controlling their use in concrete mixtures. A standard Vicat test and, a new and simple test based on agglomeration of fine particles by capillary forces of a water drop, are used to determine the water requirement and the packing density. The influence of high-range water-reducing admixture is also studied. Results show that fine mineral additions unfavourably influence the water requirement and the packing density of cement mixtures in two cases. The first case concerns additions with irregular shaped particles, which lead to loose granular structures and very high water requirement. Both Vicat and ‘single drop’ tests could determine a critical threshold for water requirement. The second case concerns blended mixtures with a low cement content, where the cement–addition particles interaction phenomenon leads to increasing water requirement comparative to other proportioning. A high amount of high-range water-reducing admixtures could attenuate this interaction phenomenon only in water saturated mixtures.