Effects of sand and potter stone on physical properties of terra cotta body

Abstract

The effects of adding pottery stone incorporating with sand and grog on physical properties of terracotta body were studied. The total amounts of sand, pottery stone and grog adding to the clay bodies were varied at 20, 30 and 40 wt%. The following green and fired (900 – 1100 °C) properties of the mixed clay bodies were investigated: plasticity, drying sensitivity, drying shrinkage, green strength, firing shrinkage, bulk density, water absorption, modulus of rupture (MOR), thermal expansion coefficient and phase composition. Based on the experimental results, it was found that sand and pottery stone could improve the physical properties of the green body by reducing plasticity, drying sensitivity, drying shrinkage and working moisture. The clay body which consists of 70 wt% clay, 11 wt% pottery stone, 11 wt% sand, and 8 wt% grog, was the optimal formula suitable for applying to production because its physical properties such as water absorption and MOR of the body fired at 950 C are similar to those of the current products of the factory. Moreover, the green properties especially plasticity, drying sensitivity and drying shrinkage of this clay body were significantly improved. As a result, the production yield would be improved as the reject caused by cracking in the drying process is reduced.