Investigation of high temperature behavior and sintering mechanism of fly ash based concretes

Abstract

Four types of refractory concretes were studied at various temperatures ranging from ambient to adopted maximal 1400 degrees C. The concretes had same matrix composition: K concretes were based on corundum aggregate; B concretes were based on bauxite aggregate and chamotte filler; while K2 and B2 concretes had 30 % of fly ash replacement in bonding agent. Fly ash was mechanically activated by means of planetary ball mill. Samples were dried at 110 degrees C during 24 hours to create standard specimens. Afterwards, the samples were preburned at 1100 degrees C and subsequently subjected to compressive uniaxial creep test conducted at various temperatures (1200, 1300 and 1400 degrees C). Thermal behavior was also investigated by dilatometry analysis starting from room temperature up to 1400 degrees C. The evolution of the refractory concretes behavior from quasi-brittle to viscoplastic was investigated and correlated to their microstructure evolution induced by sintering process. The influence of the burning temperature and procedure duration on the concretes behavior is also discussed. Creep test and dilatometry analysis helped in defining of the sintering mechanism and its parameters, and additionally explained deformation nature of the refractory concretes.