Pumice and lapillus scraps: New national environmental-friendly chance for the production of ceramic tiles

Italian pumice and volcanic lapillus scraps have been used in different percentages as alternative raw materials to
foreign feldspars in porcelain stoneware mixtures. The aim of this work was to create naturally colored support to
limit the use of artificial dyes while maintaining the technical properties of the reference product. For this
purpose, the significant presence of chromophores (Fe and Ti in particular) in by-products from extraction of
Italian volcanic pumice and lapillus was exploited. The work was carried out in collaboration with a company:
the products were made on a laboratory scale and then they were glazed and fired within the industrial production
cycle (48 min, 1210 ◦C).
The resulting slip and the fired samples were characterized by measuring the efflux time, density, linear
shrinkage, water absorption and tensile strength to evaluate the technological performance. In addition, thermogravimetric
analysis (TG), differential thermal analysis (DTA), and optical and mechanical dilatometry were
performed to study the thermal behavior of the formulations.
The obtained products could be classified as porcelain stoneware and belong to the BIa group (WA 0.5%, B.
S.>35 MPa) in accordance with UNI EN 14411 ISO 13006.