Study on the Hydration and Microstructure of B and B/Na Ion-Doped Natural Hydraulic Lime Composed with Silica Fume/Fly Ash

Natural hydraulic lime (NHL) has drawn much attention due to its environmentally friendly nature. The characteristics of both hydraulic and pneumatic components make it a potential substitute for Portland cement in surface decoration and ancient building restoration. In this study, both doping and mixing with supplementary cementitious materials were investigated. Two types of NHL3.5 were fabricated through calcination at 1200 °C with B and B/Na doping, respectively. It is noted that B ion doping is beneficial to the early compressive strength of the specimens, and B/Na doping is beneficial to the later compressive strength of the specimens. The observed outcome is that the compressive strengths of B and coupled B/Na doped NHL3.5 are higher than the blank sample due to the appearance of α’-C2S. Thereafter, the blank and doping NHL were incorporated with fly ash and silica fume. The incorporation of fly ash and silica fume could enhance the early and late hydration rate. Of the two, silica fume shows more pozzolanic effect in the early age. In the supplementary cementitious materials dosed group, pozzolanic dominates the hydration process.