ABSTRACT
The effects of particle size and particle size distributions of three clay samples, on their modulus of rupture were studied. The three clay samples were collected from natural clay deposits at Nsu; Ohiya- Umuahia; and Awo-Omamma all in south eastern Nigeria. The particle size analysis of the clay samples was done by laser diffraction in wet suspension mode and the results disclosed that Awo-Omamma clay has greater proportion of the larger sized particles, (21µm - 25µm) and (25µm - 51µm), than Ohiya clay and Nsu clay. Also the three clay samples have volume mean diameters (VMD) of 6.56µm,8.93µm and 11.29µm for Nsu clay, Ohiya clay and Awo-Omamma clay respectively.The moduli of rupture of the clay samples were also determined for the green state as well as when fired to 900°C and 1100°C. Other thermo-physical parameters of the clay samples such as porosity; shrinkage and bulk density were also determined. The 2 modulus of rupture of Awo-Omamma clay was 0.183N/mm for 2 the green state, 0.426N/mm when fired at 900°C and 2 0.544N/mm when fired at 1100°C. These values were quite 2 2 low when compared to 0.369N/mm and 0.569N/mm dry modulus of rupture values for Nsu and Ohiya clays respectively. Nsu and Ohiya clays also have superior mechanical behaviour when fired as indicated by the modulus 2 2 of rupture values of 1.04N/mm ; at 900°C and 1.51N/mm at 2 1100°C for Nsu clay, and 1.35N/mm at 900°C and 2 1.53N/mm at 1100°C for Ohiya clay. Comparison of the modulus of rupture of the three clay samples with their particle size distributions revealed that a high proportion of the larger sized particles, (21µm - 51µm) will lower the modulus of rupture of the clay. The proportions of this particle size range contained by the three clay samples are 16.14% for Awo-Omamma, 6.65% for Ohiya and 4.05% for Nsu clay. KEY WORDS: Nigerian clay, Modulus of rupture, particle size distribution, volume mean diameter, thermo-physical properties, ceramics.
