Studying the feasibility of a selection of Southern European ceramic clays for the production of lightweight aggregates

Abstract

Nine clays traditionally used in the ceramic brick and tile sector in Southern Europe were evaluated for the production of lightweight aggregates: four from Spain, three from Portugal and two from Italy. The clays’ suitability was thoroughly examined according to their capacity for pelletizing, their tendency to burst during heating, the firing temperature and their technological properties. A greater proportion of phyllosilicates over nonplastic components is directly related to the bursting of the pellets during preheating. Increased sand contents and SiO2/(∑Flux = K2O + Na2O + CaO + MgO + FeO + Fe2O3) ratios are connected to higher firing temperatures, the opposite occurring with the MgO percentage. Those clays with a higher iron content (highlighting in this study the two Italian clays and the Spanish red one) would be more optimal for the development of an expanded structure. The findings of this work show that Southern Europe holds clay deposits with enormous potential in the production of lightweight aggregates. In particular, the red clay from the Zocca deposit (Italy) is remarkable for its excellent characteristics for the production of expanded lightweight aggregates (bloating index of 24.4% and loose bulk density of 0.47 g/cm3). These raw materials could have a new market line due to the multiple applications of lightweight aggregate in construction (lightweight concrete), horticulture as well as in civil and environmental engineering.