Novel ‘inorganic gel casting’ process for the manufacturing of glass foams

A new technique for the production of glass foams was developed, based on alkali activation and gel casting. The alkali activation of soda-lime waste glass powders allowed for the obtainment of well dispersed concentrated suspensions, undergoing gelification by treatment at low temperature (75 degrees C). An extensive direct foaming was achieved by mechanical stirring of partially gelified suspensions, comprising also a surfactant. The suspensions were carefully studied in terms of rheological behavior, so that the final microstructure (total amount of porosity, cell size) can be directly correlated with the degree of gelification. A sintering treatment, at 700-800 degrees C, was finally applied to stabilize the foams, in terms of leaching of alkaline ions. Considering the high overall porosity (88-93%), the newly obtained foams exhibited a remarkable compressive strength, in the range of 1.7-4.8 MPa.