EFFECTS OF A GRINDING AID ON THE HYDRATION OF POZZOLANIC CEMENTS

THE EFFECT OF A GRINDING AID ON THE HYDRATION PROCESS OF PORTLAND AND PARTICULARLY OF POZZOLANIC CEMENTS HAS BEEN STUDIED. THE POSITIVE INFLUENCE OF THE GRINDING AID ON THE DEVELOPMENT OF MECHANICAL PROPERTIES, ESPECIALLY FOR SHORT HYDRATION TIMES. AND ON THE POZZOLANIC CHARACTERISTICS, HAS BEEN ESTABLISHED. THESE EFFECTS MAY BE ASCRIBED, WITHOUT EXCLUSION OF OTHER POSSIBLE WAYS OF INTERVENTION, TO THE DISPERSIVE ACTION OF THE GRINDING AID, EITHER ON THE CEMENT OR ON THE POZZOLAN, ALSO IN A DISPERSING AQUEOUS MEDIUM. ELECTRON MICROSCOPY REVEALED A MODIFICATION IN THE CRYSTALLINE MORPHOLOGY OF THE EARLY HYDRATION PRODUCTS. THIS MODIFICATION IS SMALL WITH RESPECT TO THE QUANTITIES OF ADDITIVE ORDINARILY USED.