Particle size distribution of limestone fillers: granulometry and specific surface area investigations

Mineral fillers can be defined as “inert materials included in a mix design for some useful purpose”. They can be added to compounds in order to complete a large variety of final properties without increasing costs or to improve specific characteristics like hardness, brittleness, impact strength, compressive strength, softening point, fire resistance, surface texture, electrical conductivity, ...etc. In Belgium, locally available limestone fillers are specifically very well-adapted for the optimisation of particle packing and flow behaviour of cementitious pastes in concrete mixes. Limestone fillers may be easily characterized in terms of chemical and mineralogical properties. These properties are fundamental for the study of the behaviour of concrete mixes in fresh state and for understanding interactions existing at the level of the Interfacial Transition Zone between aggregates and cement paste. These properties are however insufficiently discriminant and particle size, as well as shape distribution, seem to have a potential influence on physical phenomena which happen during the setting process. The aim of this paper is to compare five major techniques used to quantify the size and the shape of limestone fillers particles: laser diffraction scattering, wet sieving and image analysis for particle size measurement and BET adsorption and Blaine permeability methods for specific surface area.