| Firebricks were made from Chittarpur fireclay with the addition of Chakla nonplastic
clay grog and calcined Lolzardaga bauxite. Chakla clay was calcined both in
rotary as well as in intermitient kilns at temperatures around 1350°. Bricks were fired
to 1350° for 4 hours and were tested for their properties. Reheat shrinkage was
observed on bricks containing intermittent kiln-clay grog, and even with the addition of
25% calcined bauxite in the batch. Bricks containing 70% rotary kiln-clay grog showed
slight reheat expansion. Incorporation of finer fractions of calcined bauxite increased
firing expansion and reduced reheat expansion. Similar observations were made also
with higher calcination temperature of the bauxite. To minimise the reheat expansion
of fireclay refractories, it is desirable to avoid calcined bauxite together with rotary
kiln-clay grog and to use in case of necessity, only finer fractions of high temperature
calcined bauxite. |
