Particle size distribution, uniformity of the distribution and specific surface area (SSA) have a great influence on service properties of cement, particularly on strength. In this paper the effects of these physical parameters on strength development were studied using PC 42.5 R. In order to understand the significance of different particle size ranges in a distribution, samples having size distributions such as -10 mu m, -20 mu m, -30 mu m, -45 mu m, -32+3 mu m and -20+5 mu m were prepared from PC 42.5 R by using a laboratory scale 3rd generation separator. Additionally -32+3 mu m and -20+5 mu m fractions were added to the original PC 42.5 R in varying amounts to study SSA and uniformity effects. Same strength values were obtained for samples with a narrower size distribution but smaller SSA. Fineness is very important for strength development, particularly in the early stages of hydration. (c) 2008 Elsevier B.V. All rights reserved.