The Effect Of Particle Size And Particle Size Distribution On The Modulus Of Rupture Of Some Nigerian Clays

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.