2. Experimental procedure
The study was conducted with an industrial spray-dried powder
customarily used to manufacture porcelain tiles (STD),
obtained from kaolinitic–illitic clays, quartz, and sodium
feldspar. The chemical composition is given in Table 1. Silicon
carbide (Navarro SiC, S.A.; purity > 99.7%) of different particle
sizes, ranging from d50 = 0.5m to d50 = 55m, was used as the
foaming agent.