Utilizing of solid waste materials for producing porous and lightweight ceramics

Abstract

Some solid industrial wastes, namely, blast furnace slag and ceramic sludge, have been used to produce highly porous, lightweight ceramic materials. Nine ceramic samples were prepared. The percentage of blast furnace slag ranged from 10 to 90% by weight and ceramic sludge from 90 to 10% by weight. The addition of some limestone and sand to all batches was necessary for the precipitation of our targeted parawollastonite ceramics. The prepared samples, weighed, well mixed, and then pressed into disks by using uniaxial pressure (40 MPa). The optimum sintering conditions were 1100 °C for 1 h. Various experimental techniques were performed, including, X-ray diffraction, porosity, density, SEM, and dielectric determination. XRD analysis ensured that the obtained ceramic materials are primarily composed of parawollastonite and gehlenite phases with fibrous, columnar, and tabular crystals as shown in SEM photographs. The porosity of samples was in the range of 28.83–40.50% and the density ranges were from 1.613 to 2.182 g/cm3, which qualified them for use in construction purposes. The dielectric properties including the relative dielectric constant (ε′), and dielectric loss (ε") were measured at 200 measuring points in the frequency range of 50 Hz up to 8 MHz. The electric and dielectric values of sample BFS5 (50% blast furnace slag + 50% sludge) were the highest values among the other prepared mixtures. So it could be used as a poor semiconductor at ≤ 2 MHz, and as fair semiconductor material at >2 MHz. The electric measurements confirmed very low electrical conductivity values for the ceramic materials (0.001–50.82 μS/cm). This indicated the ability of their preparation as poor to fair semiconductors. Hence the results showed that the prepared lightweight parawollastonite and gehlenite ceramic could be used in low dielectric materials in the electronics covering manufacturing.