Some effects of limestone fillers as a partial substitute for cement in mortar composition

Limestone filler is a raw material that is already used in several applications like paints, bricks, bituminous mixes, … Moreover, and particularly in Belgium, classical additions like fly ashes and blast furnace slags become rare. There is a need for new additions that could have a positive effect on the properties of the fresh and hardened cementitous composites.
Substitution of limestone filler in Portland cement and blast furnace slag cement has been realized between 15 and 30% in mass.
In addition to the characterization of the powder itself – specific mass, specific surface and laser granulometry – the problem of the water demand has been analysed: it seems that it remains constant with the substitution rate. Electric conductivity has also been performed in order to study the evolution of the “dormant” period.
Tests on hardened mortars concerned the mechanical properties, the evolution of the porosity and the durability. The K factor indicates a higher value and the porosity seems to be better in the case of blast furnace slags cements, partially due to a very low diameter of the slags particles.
Oxygen permeability doesn’t seem to be influenced by the filler while capillary absorption increases with substitution rate. Finally, chloride penetration, sulphate resistance and carbonation rate show quite interesting behaviours, leading to the conclusion that this material needs again more investigations in order to define optimum application conditions in cementitous matrixes