New optimized method for low-temperature hydrothermal production of porous ceramics using diatomaceous earth

Abstract The aim of this study was to test the diatomaceous earth from a deposit near Rožden Village (Macedonia) as a raw material for low temperature hydrothermal production of porous ceramics. Hydrothermal synthesis of porous ceramics has been carried out under saturated steam pressure at 130 °C for a period of 1, 2 and 3 h. The objective of this work was to investigate the impact of slaked lime, autoclave curing time, autoclaving temperature and compaction pressure on the compressive strength and porosity of the products. During the hydrothermal synthesis, newly obtained calcium silicate hydrate dominates which give positive effect to the compressive strength and product porosity confirmed by X-ray powder diffraction. Moreover, a calcite was also evidenced by FTIR spectroscopy whose presence additionally increases the compressive strength of the hydrothermal products. The products obtained during the low-temperature hydrothermal reaction are classified as light porous ceramics with bulk density ranging from 0.71 to 0.91 g/cm 3 and compressive strength within 14.7–19.4 MPa.