Phase analysis and hydration behavior of fine and coarse particle fractions contained in a commercial Portland cement

Abstract

A fine (< 3.5 µm) and a coarse (11 − 63 µm) particle fraction was separated from a commercial OPC and their composition, hydration behavior and impact on engineering properties were extensively studied. The fine fraction showed decreased alite and C3A (cubic), increased calcium sulfates and limestone contents, whereas C2S, C3A (orthorhombic) and C4AF were mostly unchanged. The phase distribution of the fractions differs to prior literature what has been evidenced using more sophisticated analytical methods like Q-XRD including Rietveld refinement combined with e.g. salicylic acid extraction. The fine fraction produces particularly high early strength through rapid C-S-H and ettringite formation while the coarse fraction contributes mainly to the final strength by C-S-H formation only. The results clearly illustrate the strong impact of the fine particle fraction on the early engineering properties of bulk cement sample, whereas the coarse particle fraction contributes more to final strength.