INFLUENCE OF THE FINENESS OF POZZOLAN ON THE STRENGTH OF LIME NATURAL-POZZOLAN CEMENT PASTES

The fineness of a cement is an important factor affecting the rate of strength development. This paper examines the importance of the finene ss of natural pozzolans to the strength development of lime-pozzolan c ements (LPCs). A natural pozzolan from Bolivia, which is typical of na tural pozzolans found in South and Central America, was ground to vari ous finenesses, blended with lime with a mass ratio of 80:20, and the resulting LPC was used to make hardened cement paste cylinders. In som e pastes 4% sodium sulphate or 4% sodium chloride activator was used t o enhance strength development. Strengths of the cylinders were measur ed at ages from 3 to 90 days during continuous moist curing at 50-degr ees-C. The experimental results show that there is a good linear corre lation between the Blaine fineness of the natural pozzolan and compres sive strength at all ages and for all pastes. The fineness of the natu ral pozzolan has its most significant effect on early strength gain. T he addition of chemical activator increases both the rate of strength gain and the sensitivity of strength gain to fineness.