*2.1. Batch Calculation and Samples Preparation*

Nine ceramic samples were prepared from arc furnace slag (Al-Ezz-Dekheila Iron Steel Company, Alexandria, Egypt) and ceramic sludge (Ceramica Venezia, Cairo, Egypt). The arc furnace slag content in their composition varied from 10 wt.% to 90 wt.% at 10 wt.% intervals, and accordingly, the ceramic sludge content varied from 90 wt.% to 10 wt.%. The ceramic batches were prepared by calculating the appropriate proportions of arc furnace slag and ceramic sludge. The required silica and calcium oxide for all compositions were obtained from silica sand and limestone, respectively. The other minor elements present in the industrial wastes were considered during batch calculation. X-ray fluorescence (XRF) was used for chemical analysis of both waste materials (Table 1). The ceramic sample compositions were calculated based on ceramic sludge percentage with each successive increase in arc furnace slag percentage. These samples were designated AFS1, AFS2, AFS3, AFS4, AFS5, AFS6, AFS7, AFS8, and AFS9, as listed in Table 2.

Approximately 10 kg, as representative samples, of arc furnace slag, ceramic sludge, limestone, and silica sand were collected and crushed into −100 mesh powders. An adequate representative quantity for all stages of the laboratory investigation was obtained using the quartering technique. The prepared ceramic batches, after being accurately weighed to yield approximately 4 g for each sample, were closely dry-mixed in a ball mill for approximately 40 min until they became utterly homogeneous. Approximately 5% water was added to each sample as a binder, and then the powder samples were shaped into cylinders of 40 mm diameter and 4 mm thickness via uniaxial pressing at 20 MPa. The prepared ceramic batches were dried in an oven at a temperature of 100 ◦C for 24 h and then sintered at 1100 ◦C for one hour; this is shown in Figure 1. Figure 2 exhibits the visual appearance of the prepared samples.


**Table 1.** Chemical analysis of used raw materials.


**Figure 1.** Schematic presentation of ceramic production from industrial wastes.

**Figure 2.** The surface appearance of ceramic samples prepared from industrial wastes after being treated at 1100 ◦C for 1 h.

Sample AFS5 was chosen, representing the average composition of all other samples, to study the effect of different sintering temperatures on the developed phases and microstructures.

## *2.2. X-ray Diffraction*

The precipitated phases were identified with X-ray diffraction using a Bruker AXA diffractometer (D8—ADVANCE, Bruker, Germany) with Cu–Ka radiation, operating at 40 Kv, 40 mA, and a scanning rate of 10◦/min.
