THE STUDY ABOUT EFFECTS OF UNBURNT CARBON OF FLY ASH ON PACKING FRACTION AND FLUIDITY OF PASTE

摘要

It is well known that the fluidity of concrete is strongly affected by the packing properties of a fine powder such as cement and fly ash. The packing properties of fine powders are affected by the size distribution of powders. We found out that the unburned carbon affects the packing properties of fly ash. This study describes the effect of unburned carbon on the packing properties of powder and the fluidity of paste in the system with fly ash and cement. We first added the carbon black, that is composed with pure carbon, to fly ash, and examine the effect of unburned carbon on the packing properties of powders and the fluidity of paste. From the result, the unburned carbon enhanced the flocculation of particles, consequently providing lower packing fraction of powder and poor fluidity of paste. It could be concluded that the packing fraction of fly ash was estimated by considering both the fractal dimension of particle-size distribution and the amount of unburned carbon.