Characterization and evaluation of the pozzolanic activity of Egyptian industrial by-products: I: Silica fume and dealuminated kaolin

• Published in: Cement and concrete research 2001-03, Vol.31 (3), p.467-474
• Main Authors: Mostafa, N.Y., El-Hemaly, S.A.S., Al-Wakeel, E.I., El-Korashy, S.A., Brown, P.W.
• Format: Article
• Language: English
• Subjects: Aggregates and other concrete constituents; Applied sciences; Buildings. Public works; By-products; Calcium silicate hydrates; Cement concrete constituents; Concrete additives (fillers, pozzolanic and hydraulic materials); Conduction calorimetry; Dealuminated kaolin; Exact sciences and technology; FTIR; Materials; Pozzolanic activity; Silica fume
• ISSN: 0008-8846; 1873-3948
• DOI: 10.1016/S0008-8846(00)00485-3

Silica fume (SF) and dealuminated kaolin (DK) from Egyptian sources have been characterized chemically and mineralogically, and a comparative study of their reactivities toward lime were conducted using isothermal conduction calorimetry and an accelerated chemical method. The kinetics of SF–lime and DK–lime reaction were investigated in suspension. Unreacted lime and combined water were determined as function of time, and the hydration products were identified with X-ray diffraction (XRD) and SEM combined with EDX. DK has a much higher surface area (90.5 m 2/g) than SF (18.6 m 2/g) and exhibits much higher pozzolanic activity, especially during early hydration. A low-density sponge-like CSH was formed, from both SF and DK at low lime contents (20% CH), and a more dense CSH was formed at higher lime contents (40% CH).