Thermal stability and pozzolanic activity of calcined kaolin

Abstract Standard illite (American Clay Society, IMt-1) was calcined at 650,790 and 930°C for 100 minutes. Both the raw and calcined samples, before and after being mixed with Ca(OH) 2 in the presence of simulated cement pore solution, were studied by DTA, TG (for raw illite), XRD, SEM, EMPA and chemical solubility. The reaction rate of the mixtures was monitored by a chemical shrinkage test. Technological properties of the untreated and calcined illite-cement mortars were studied by theology (flow) and by a compressive strength test after reaction for 2, 7, 28 and 91 days. The current investigation revealed that illite has low pozzolanic activity. Dehydroxylation at 650°C does not upgrade it significantly. Further calcination at 790°C brings about considerable activation but it still does not qualify as a pozzolan. Calcination at 930°C produces the highest pozzolanic activity. Compressive strength of the mortar with 930°C illite is 79% of that of reference ordinary portland cement.

[1]  F. Glasser,et al.  Pozzolanic activation of metakaolin , 1992 .

[2]  J. Hower,et al.  The mineralogy of illites and mixed-layer illite/montmorillonites , 1966 .

[3]  G. Brindley,et al.  Thermal, oxidation and reduction reactions of clay minerals. , 1987 .

[4]  J. Pera,et al.  Hydration reaction and hardening of calcined clays and related minerals V. Extension of the research and general conclusions , 1985 .

[5]  M. Surana,et al.  Estimating reactivity of pozzolanic materials by a spectrophotometric method , 1990 .

[6]  H. El-Didamony,et al.  Metakaolin—lime hydration products , 1984 .

[7]  M. Ayub,et al.  Pozzolanic properties of burnt clays , 1988 .

[8]  T. Knudsen.  On the possibility of following the hydration of flyash microsilica and fine aggregates by means of chemical shrinkage , 1985 .

[9]  M. J. Vold.  Differential Thermal Analysis , 1949 .

[10]  M. Murat.  Hydration reaction and hardening of calcined clays and related minerals. I. Preliminary investigation on metakaolinite , 1983 .

[11]  W. Price.  POZZOLANS - A REVIEW , 1975 .

[12]  H. Taylor.  Chemistry of Cements , 1938, Nature.

[13]  M. McBride.  Chemistry of Clays and Clay Minerals , 1988 .

[14]  Torben Knudsen,et al.  Chemical shrinkage of portland cement pastes , 1982 .

[15]  F. Glasser,et al.  Phase relations in the system CaOAl2O3SiO2H2O relevant to metakaolin - calcium hydroxide hydration , 1993 .

[16]  S. Diamond.  Concrete admixtures handbook: V.S. Ramachandran, editor. Noyes Publications, Park Ridge, NJ 07656. 1984. (cloth $84.00) , 1986 .

[17]  F. Lea.  The chemistry of cement and concrete , 1970 .

[18]  Rc Mielenz,et al.  Effect of Calcination on Natural Pozzolans , 1950 .

[19]  A. Neville.  Properties of Concrete , 1968 .

[20]  M. Murat.  Hydration reaction and hardening of calcined clays and related minerals , 1983 .

[21]  V. I. Babushkin,et al.  Thermodynamics of silicates , 1984 .

[22]  J. Środoń.  X-ray powder diffraction identification of illitic materials , 1984 .

[23]  D. N. Hinckley.  Variability in “crystallinity” Values among the Kaolin Deposits of the Coastal Plain of Georgia and South Carolina , 1962 .