*2.1. Batch Calculation and Glass Preparation*

Eight glass compositions were designed based on cordierite (Mg2Al4Si5O18) and wollastonite (CaSiO3) systems selected for the current project. The cordierite content in these compositions varies from 10 to 80 at ten wt% intervals, and consequently, the wollastonite content ranges from 90% to 20%. These studied samples were G10, G20, G30, G40, G50, G60, G70, and G80. These numbers denote the wt% of the cordierite and the rest being the wollastonite components. For example, G40 means that this glass composition contains 40wt% cordierite component and the rest, 60wt% wollastonite component. The batches related to these compositions were designed by calculating the appropriate proportions of solid wastes represented in by-pass cement dust, magnesite, kaolin, and silica sand. Table 1 shows the chemical compositions of the raw materials used. Table 2 shows glass compositions in the oxide percentages and raw materials used. These batches were ground in a ball mill for about 45 min, then they were melted in platinum crucibles in an electrically heated globar furnace at temperatures ranging from 1550 ◦C to 1600 for 2–3 h, according to the batch composition. It was noted that glasses rich in cordierite were highly viscous and needed higher melting temperatures. The melting temperature increased with an increase in the percentage of cordierite contents (that is, the degree of viscosity increases from G10 to G80).

**Table 1.** Chemical analyses of raw materials used in the batch preparation.




Where, \* cord = cordierite, wol. = wollastonite, Mag. = magnesite.

After melting and refining, the resulting bubble-free melts were cast onto a hot steel marver into steel molds in the form of buttons (about 20 mm and 9 mm thickness) as rods of 50 × 10 ×10 mm. The hot glass samples were transferred to preheated electric muffle furnace to avoid thermal shock.
