Fabrication and characterization of non-foamed and foamed geopolymers from industrial waste clays

In this work, an attempt to recycle Cyclones' and Feeders' waste-clays in fabrication of non-foamed and foamed geopolymers was performed. These industrial solid wastes are created as by-products from refractory industry. Firstly, the starting clay-wastes were converted into metakaolin by calcination at 850 °C. The calcined and uncalcined wastes were analyzed by X-ray fluorescence, X-ray diffraction and FT-IR. The calcined and uncalcined waste-clays were mixed with the suitable amounts of alkali activator to produce non-foamed and foamed geopolymers. The phase composition, physical properties, compressive strength and microstructure of the prepared geopolymers were examined by X-ray technique, Archimedes water-displacement method, hydraulic mechanical testing machine, and scanning electron microscope, respectively. The results revealed that non-foamed and foamed geopolymers were successfully prepared from the selected waste clays. The geopolymer that prepared from calcined Feeder's waste-clay exhibited the best compressive strength (29.4 MPa) among the other non-foamed geopolymers. The geopolymer prepared from 50% calcined Feeder's waste-clay and 50% calcined Cyclone's waste-clay exhibited also good compressive strength (19.6 MPa). Moreover, geopolymer foam with suitable compressive strength (8.46 MPa) was prepared from calcined Cyclone's waste-clay. The foamed geopolymer had higher apparent porosity and lower bulk density than the non-foamed geopolymers.