Effect of volcanic ashes addition on ceramic properties of clayey materials from Koutaba (Western Cameroon)

This study aimed to determine the best composition of ceramic pastes from clays and volcanic ashes mixture. Two samples of clay from Koutaba and one of volcanic ashes from Foumbot (western Cameroon) were collected and physically characterised (granulometry and plasticity). Four formulations were prepared with 60wt% of ball clay; 10, 20, 30 and 40wt% of kaolin; and 30, 20, 10 and 0wt% of volcanic ashes (VAs). Brick samples of 80 × 40 × 15 mm were made and heated at 1050, 1100 and 1150 °C. Physico-mechanical and technological tests were done on fired products. Results showed that ball clays were plastic (Ip = 48.52%) compared to kaolin (Ip = 6.05%). Fired products displayed brown colour, accentuated with temperature and the increase in volcanic ash. Metallic sound was obtained beyond 10wt% VA. With increase in VA, linear shrinkage increased between 1050 and 1100 °C, then decreased between 1100 and 1150 °C. Low shrinkage ( 36 MPa) beyond 10wt% VA at 1150 °C. Hence, ceramics with 20 and 30wt% VA with heating temperature of 1100 and 1150 °C are suggestible.