Effect of accelerators on Ca(OH)2 activated ground granulated blast-furnace slag at low curing temperature

Abstract The early effects of three accelerators on a Ca(OH)2 activated ground granulated blast-furnace slag binder at low curing temperatures are discussed. The compressive strength, hydration kinetics, hydration products, and microstructures were investigated by isothermal calorimetry, X-ray diffraction, mercury intrusion porosimetry, scanning electron microscopy, and nuclear magnetic resonance. Results show that accelerators continue to promote the strength development of pastes in the early stage during low-temperature curing, especially with sodium sulfate, which exhibits a higher strength and hydration degree in the early stage. However, accelerators cannot effectively improve the pore structure at low-temperature curing, which severely restricts the development of strength, compared with that at 20 °C. Furthermore, a good correlation was found between the initial strength development and the limit equivalent ionic conductivity (LEIC), suggesting that LEIC influences the reaction acceleration of blast-furnace slag at an early age.