Effects of nano-limestone on hydration properties of tricalcium silicate

Abstract

In this research, the influences of nano-limestone (NC) on tricalcium silicate (C3S) hydration, including early hydration rate, setting time, Ca(OH)2 content, quantification of C–S–H, micrographs of hydration products and compressive strength, were investigated by different methods. Calorimetry results show that the first and second exothermic peak of C3S with 1 mass% NC is ~29 and ~5% higher than that of control sample and the second peak appears 32 min in advance. Besides, the total hydration heat of C3S with 1 mass% NC increases by 10.08% compared to control sample at 72 h. The initial and final setting time of C3S with 1 mass% NC shortens by 23 and 17 min, respectively. In addition, thermal analysis results show that adding NC leads to higher Ca(OH)2 and C–S–H content at all ages (1, 3 and 28 days). All of the above results imply that the hydration progress of C3S is accelerated by NC. Correspondingly, the compressive strength of C3S with 1 mass% NC increases by 9.88% at 28 days. Besides, EDS results reveal that the Ca/Si ratio of C–S–H gel decreases after NC modification. However, excessive content NC (4 mass%) reduces the acceleration effect of NC on C3S hydration and finally leads to relative low content of Ca(OH)2 and C–S–H compared with C3S sample containing 1 mass% NC.