Dissertations

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Browsing Dissertations by Subject "Different temperatures."

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    Investigation of the compressive strength of ntawo ball clay fired to different temperatures at different rates of temperature rise
    (Kyambogo University (un published work), 2017-12) Byekwaso, Ronald
    This study was to investigate the compressive strength of fired Ntawo Ball Clay found in Mukono District in Central Uganda. The clay sample was first analyzed using X-ray Diffraction Spectrometer Model RIX3000 to determine the relative abundance of the chemical components and then compressive strengths were determined. Ball clay of particle size 45.0 μm was used to produce 150 rectangular clay slabs fired in an electric furnace, model P59 l 0. They were then subjected to compressive strength test by first determining the breaking force for each sample using a compressive test machine, compact 500Sn-12994917 on samples fired at different rates of temperature rise, ranging between 2°C min- 1 and 6°C min-1 in intervals of 1°C min-1 for set firing temperatures. The compressive strength tests were then carried out on another set of samples fired at set rates of temperature rise to different firing temperatures ranging between 500°C and I 000°C in intervals of I 00°C. The compressive strength of fired tawo ball clay was found to decrease with increase in rates of temperature rise between 2°Cmin-1 and 6°Cmin-1 for the six firing temperatures. For temperatures of 500°C to I 000°C in intervals of I 00°C, the percentage decrease in compressive strength ' ere 11 %, 3%. 3%. 8%, 2.9%, and 11 % respectively. At a level of significance a = 0.05 and a = 0.0 I, it was established that compressive strength was related to the rate of temperature rise. The study further revealed that compressive strength increased with increase in firing temperature. The percentage increase was 279%, 273%, 247%, 257% and 279% for the rates of temperature rise between 2°Cmin-1 and 6°Cmin-1 respectively, overall average percentage increase being 267%. At a level of significance a= 0.05 and a = 0.0 I, compressive strength depended on firing temperature ntawo clay was found to be composed of mainly silica (67.20%), alumina ( 18.20%), ferrous oxides (2 .83%) and other fluxing oxides such as CaO (0.31 %). K20 (0.98%), and a20 (0. 19%), among other compounds. The compressive strength of fired samples decreased with increase in rates of temperature rise during firing between 500°C and I 000°C. Other investigations should be made to find out the effect of firing beyond I 000°C and firing at a rate above 6°C min1 on the compressive strength, and the effect of changing the mineralogical composition of clay on the compressive strength.
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    Investigation of the compressive strength of ntawo ball clay fired to different temperatures for different holding times
    (Kyambogo University (un published work), 2017-12) Isabirye, Jeromy Moses
    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.