Improving properties of Portland cement-blast furnace slag blended paste through sodium bicarbonate-induced carbonation

Abstract

The addition of NaHCO₃ has the potential to enhance properties of concrete by facilitating internal carbonation. This study investigates the effects of the incorporation of NaHCO₃ into ordinary Portland cement-blast furnace slag paste. The results show that the addition of NaHCO₃ had an impact on the hydration process and increased the heat of hydration on all the slag samples. NaHCO₃ caused internal carbonation and facilitated the formation of calcium carbonate and different carbon-based AFm phases, such as monocarbonate. The incorporation of NaHCO₃ improved the pore structure of the paste and enhanced resistance against chloride penetration. The chloride migration coefficient of the Portland cement paste sample was reduced up to 96.5% with the incorporation of 2% NaHCO₃ at 70% slag replacement. The compressive strength of the samples also showed an improvement with 1% NaHCO₃ addition increasing the early age strength and 2% NaHCO₃ addition increasing the matured age strength.