Effects of rice husk ash on the physical properties of terra cotta body

Abstract

The objective of this thesis is to study the effects of rice husk ash (RHA) on the physical properties of terra cotta body either before or after firing in order to know the properties of RHA mixed terra cotta body before applying in the real production. RHA was progressively incorporated with the normal terra cotta mixed clay body at 3, 6 and 9 wt%. in addition, the total quantity of silica sand around 5 wt% in the normal terra cotta body was also replaced by RHA. Terra cotta mixed clay bodies with a range of RHA contents were prepared and then fired at 900, 950, 1000, 1050 and 1100 °c. The following properties of mixed clay bodies were investigated: plasticity, drying rate, drying shrinkage, green strength, firing shrinkage, bulk density, water absorption, modulus of rupture (M.O.R) and phase analysis. It was found that the plasticity, green strength and drying rate were improved, especially the drying and firing shrinkage were significantly reduced. Moreover, the complete replacement of silica sand by RHA in the mixed clay bodies increased the modulus of rupture, especially when the firing temperature was over 950 °c. Although the density of fired body decreased and the water absorption increased with the increasing in RHA content, all the results showed that the substantial quantities of RHA could be successfully incorporated into the terra cotta mixed clay bodies without any deterioration in the quality of products.