Dolomite and limestone micro filler: early-age properties and soundness on blended cement

MARCHETTI, M.G.; IRASSAR, E. F.; DI SALVO BARSI, A.; RAHHAL, V. F.; TREZZA, M.

Praga

Congreso; 15th International Congress on the Chemistry of Cement (ICCC 2019); 2019

This study investigates the physical and chemical effects of dolomite microfiller in Portland blended cements comparing to limestone filler. Dolomite (CaMg(CO3)2) is limited as filler due to the potential dedolomitization in high alkaline environment of the paste. Natural Dolomite (D) and limestone (L) were ground fine particles with median size of 10 m and included as partial replacement to ordinary Portland cement (OPC) up to 30% by weight. The packing density and the water film thickness were evaluated for both filler with similar particle size distribution. For 10, 20 and 30% of replacement, the effect of dolomite on water demand, the isothermal calorimetric, the setting time and the compressive strength at 1, 2, 7, 28 and 90 days was determined. At 2, 28 and 90 days, the hydration compounds were determined by XRD and the CH quantified by TG analysis at 28 days for C0, C20D and C20L. Dolomite filler as occurred with limestone filler increases the packing density and the specific surface area, but it improve the paste workability measured by the mini-slump test and the mortar flow due to the complementary effect on the WTF. Dolomite particles act as sites for nucleation and growth of cement hydration products stimulating the early hydration of PC as shown the calorimetric curve and reducing the setting time. Early compressive strength depends on stimulation and dilution effects of D. At later ages, the formation of AFm phases (Hc and Mc) occurs without the formation of brucite indicating that dolomite remains stable. D-PC performs comparably to L-PC without noticeable deleterious reactions.