Effect of Fly Ash Fineness on Compressive Strength, Total Pore Volume and Pore Size of Blended Cement Paste

Abstract

This paper presents an experimental investigation on the effect of fly ash fineness on compressivestrength, total pore volume, and pore size of hardened blended cement pastes. Class F fly ashwith two finenesses; an original fly ash and a classified fly ash with median particle size of 19.1 and6.4 micron, respectively were used to partially replace Portland cement type I at the rate of 0, 20, and40% by weight of binder. The water to binder ratio (W/B) of 0.35 was used for all the blended cementpaste mixtures.

Tested results indicated that the blended cement paste with classified fly ash produced pastewith higher compressive strength than that with original fly ash. The pore size of blended cementpaste was significantly affected by the rate replacement and fineness of fly ash. The replacement ofPortland cement by the original fly ash increased the total pore volume but decreased the capillarypore size of the paste. The incorporation of the classified fly ash decreased the total pore volume andthe capillary pore size of the paste as compared to that with ordinary fly ash. The total pore volumeand capillary pore size of the pastes decreased as a result of the addition of finer fly ash at allreplacement levels.