COMPARISONS AMONG MAGNETIC AND NONMAGNETIC FLY-ASH FRACTIONS - STRENGTH DEVELOPMENT OF CEMENT FLY-ASH MORTARS

Magnetic extractions from aqueous-fly ash suspensions produced magneti c and non-magnetic fly ash fractions. Several fractions were obtained from an original fly ash (T0), from T0 and further grinding, and from a ground fly ash (T6O). Magnetic and non-magnetic samples were charact erized: chemical composition, granulometric data, specific gravity and specific surface area. Workability studies on mortars containing thes e fractions were carried out. Generally, non-magnetic fractions yielde d mortars with similar or higher flowability than mortars containing t he corresponding magnetic fractions. On the other hand, compressive st rength development studies showed that non-magnetic fractions are more pozzolanic than magnetic ones; moreover, optimum replacing percentage of cement by fly ash fractions was 45% for non-mechanically treated s amples, whereas for ground fractions optimum values were 30% for non-m agnetic samples and 45% for magnetic ones. Copyright (C) 1996 Elsevier Science Ltd