Production of lightweight gypsum using a vegetal protein as foaming agent

The paper deals with the production of lightweight gypsum composites by means of a vegetal protein foaming agent. Two manufacturing methods, which basically differ in the physical state of the foaming agent used, have been proposed and the relative experimental results have been compared and discussed. The gypsum foam samples have been characterized from several points of view (physical, mechanical and microstructural). Thermal and acoustic properties and also porosity have been investigated in order to evaluate the insulation features of the lightweight gypsum composites. The addition of foaming agent strongly affected the mechanical performance of all the samples and led to a significant modification of the post-cracking behavior. Differences observed in the morphology and porosity, related to the two manufacturing methods, are due to the method of pore-formation, especially to the different amounts of air insufflated within the gypsum pastes which influence, in addition to the porosity, the final microstructure and consequently the insulation performances of the gypsum foams. In fact, the more porous samples, obtained from the addition of the liquid foaming agent, showed both the lower values of thermal conductivity and the better values of sound absorption coefficient, leading to a final lightweight products characterized by improved insulation properties.