DBPapers

RECYCLING OF FLY ASH IN CEMENT MANUFACTURING

AUTHOR/S: J. PACEAGIU
Sunday 1 August 2010 by Libadmin2010

10th International Multidisciplinary Scientific GeoConference - SGEM2010, www.sgem.org, SGEM2010 Conference Proceedings/ ISBN 10: 954-91818-1-2, June 20-26, 2010, Vol. 2, 925-932 pp

ABSTRACT

This paper presents the results obtained by utilization of pulverized coal fly ash both as
raw mix component for Portland cement clinker and as admixture to cement type CEM
II/B-V, too. The fly ash was analyzed from point of view of chemical, mineralogical
and of radioactivity content. Two samples of raw mixes were prepared, one with raw
materials as a reference sample consisting from limestone, clay, sand and pyrite cinder,
and another with 10.14% fly ash instead of clay. Raw mixes were ground at a fineness
expressed by a residue R009 of about 10%. Grindability and burnability of raw mixes
were evaluated as well as the heat theoretic consumption. Both raw mixes were sintered
at 1450oC. The produced clinkers were analyzed by chemical, optical microscopy and
X-ray diffraction analyses. They are characterized by high silica modulus (approx. 2.4),
a lime saturation factor of 0.96 and alumina modulus of 1.45. From mineralogical
composition point of view do not appear important modifications compared with a
clinker having same modulus characteristics but which contains clay as silica/aluminous
component in raw mix. The cements were obtained through grinding of laboratory
clinkers with addition of gypsum, with and without addition of 30% fly ash up to
fineness about 3500 cm2/g. Physical and chemical characteristics of cements comply
with requirements of SR EN 197-1. Besides this, the cements showed comparable
mechanical strength values at 2, 7 and 28 days; the cement without fly ash additions
attained the strength class 42.5N, while the cement with 30% fly ash attained class
32.5R.

Keywords: fly ash, sintering, clinker, cement, compressive strength

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