Preparation and characterization of low-cost wollastonite and gehlenite ceramics based on industrial wastes

• Waste materials recycling through preparation of useful materials is our target. • Porous ceramic depends on wollastonite and gehlenite was prepared. • Porous ceramic materials having the mentioned phases are highly porous materials and can be used as wall tiles. Eight ceramic samples were prepared from bypass cement dust and ceramic sludge. Bypass cement dust was generated during cement industries, and ceramic sludge is produced through ceramic glaze preparation. The prepared ceramic samples contained 10-80 wt% of bypass cement dust and 90–20 wt% ceramic sludge, respectively. The samples were formed in disk-shaped specimens using the uniaxial pressing (20 MPa) and sintering temperature at 1100 °C for one hour. Various techniques were used in the present work, including X-ray diffraction, FTIR, porosity, density, SEM, and dielectric determination. The obtained ceramic materials were mainly composed of wollastonite and gehlenite phases with fine coarse-grained crystals, as shown in SEM photographs. The final product possessed density values ranging from 1.280 to 1.574 g/cm 3 , open porosity ranging from 43.2 to 58.1% making them suitable for building materials applications. The dielectric properties, the relative dielectric constant (ε'), and dielectric loss (ε“) were measured at 200 measuring points at the range of frequency from 50 Hz to 8 MHz. The dielectric loss and dielectric constant values are relatively low (0.595 to 0.714) and (9.141–12.125) at 50 Hz, respectively, while the electric conductivity ( σ) values were indicative for insulator materials ( σ ≤ 10 −2 µS/cm for samples CS1–Cs5) at low electric frequencies at 50 Hz, whereas referring to semiconductor materials ( σ < 10 9 µS/cm) at the higher electric frequencies. The materials obtained from the bypass cement dust and the ceramic sludge mixtures are characterized by low dielectric constant and dielectric loss values, making them suitable for electrical and electronic industrial applications.