Investigation of the compressive strength of ntawo ball clay fired to different temperatures for different holding times

Abstract

This study focused on ball clay from ntawo deposit from Mukono District, in central Uganda with respect to its compressive strength. The chemical compounds by percentage weight were determined using RIX 3000 Spectrometer machine. The compressive force was determined by SOOS -1299417 machine. One hundred and fifty samples of Ntawo ball clay fired from 500°C to I 000°C at intervals of I 00°C were used to find out how holding time affected compressive strength for each set firing temperature. The same number of samples were used to investigate how the compressive strength of fired tawo ball clay to find out how they were affected by firing temperature for each set holding time between 20 minutes and 60 minutes at intervals of I 0 minutes. The tawo ball clay was found to contain 67.2% of silica, 18.2% of alumina, 2.83 % of Fe203 and 1.84% of fluxes. The compressive strength decreased from 4.2% to 0.4% withholding time for firing between 500°C and 800°C. The compressive strength variation was negligible, less than I% for temperatures beyond 900°C to I 000°C. The highest compressive strength was 25.45 MPa, obtained by firing to a temperature of I 000°C. In all cases compressive strength increased by 298±7 % for all firing temperatures at each of holding times of 20, 30, 40, 50 and 60 minutes respectively. The compressive strength of ball clay beyond 800°C does not need longer holding time. It was further established that the compressive strength of fired clay depended on holding time when fired to various firing temperatures and the compressive strength of fired clay depended on firing temperature when the firing is held for holding time were tested at ex:= 0.01 and ex:= 0.05 levels of significance. The compressive strength for ball clay fired above 1000°C and holding time exceeding 60 minutes is worth investigation in order to find out whether any change in the mineral compounds of ball clay affect the above results.