Natural hydraulic lime (NHL) has gained a great deal of attention as an eco-friendly construction material, but its application has remained very limited due to its insufficient mechanical properties. The addition of mineral admixture to NHL has been considered as a means of addressing this drawback and improving the mechanical properties for future commercialization. The effects of adding a mineral admixture such as blast furnace slag (BFS) or anhydrite (AH) to NHL on the hydration properties were systematically investigated in this study. Local Korean NHL (K-NHL) was synthesized using domestic lowgrade limestone. The hydration properties of the NHL products were then investigated as a function of the hydration time and the addition ratio of inorganic additives. Through an investigation of the hydration properties of NHL pastes mixed with BFS and AH, Al-based compounds such as calcium aluminate hydrates (C4AH13) and ettringite (3CaO • Al2O3 • 3CaSO4 • 32H2O) were observed at early hydration time. The formation of calcium silicate hydrates (C-S-H) increased with enlargement of the amount of inorganic additives. The compressive strength and setting time were improved due to increased quantities of these hydration products.

Keywords: Limestone, Natural hydraulic lime, Blast furnace slag, Anhydrite, Hydration.