Natural limestone fillers : physical and chemical properties with regard to cement based materials performances

Natural limestone fillers are available on the market and supplied by limestone aggregates industry but also ornamental stone suppliers. The use of limestone fillers in cement based concrete requires a thorough characterization of the materials. Physical and chemical properties will influence behaviour of the fresh and hardened concrete. Impurities may affect cement hydration process, delay the setting time and decrease the compressive strength.
Six types of limestone fillers, in the form of finely ground limestone powders, have been collected in Belgium (more precisely in Wallonia Region). They differ from each other through their physical properties (Blaine fineness, particle size distribution, water demand) but also chemical and mineralogical properties (presence of impurities such as sulphate, clay, quartz and dolomite). Special attention has been focused on clay content and type influences; limestone fillers have been artificially polluted with clays in order to investigate their behaviour in cement based mortars.
The effect of the nature and the substitution rate of the fillers on the properties of mortars are investigated. Relationships between physico-chemical properties of the fillers and the properties of mortars clearly indicate a harder influence of the limestone composition on the fresh than the hardened properties.