Fabrication of a Concrete Roof Tile by Geopolymerization of Red Clay with Container Glass Wastes

We report the production of concrete roof tiles using a red clay-based geopolymer binder with container glass waste and river sand as a concrete filler. Clear and colored container glass wastes were separately ground to powder and blended with low-grade red clay to achieve a SiO2/Al2O3 ratio of approximately 7.0. The powder blends were converted to geopastes with a solid-to-alkali solution ratio of approximately 0.8 using a 12-molar alkali activator solution containing a mixture of potassium hydroxide and sodium hydroxide. Rheological analysis showed that the geopaste binders with transparent and colored glass powders exhibited high shear thinning behavior. A higher viscosity was observed for the geopaste with colored glass powder due to the presence of colorants. Fine and coarse particles of river sand were prepared and mixed with different ratios of geopaste binder to river sand of 1:2.0, 1:2.5, and 1:3.0, respectively. All geopaste and river sand formulations were poured into acetate molds and heated in a metal chamber at 80 °C for 24 h, then aged at room temperature for 14 d. The highest flexural strength of 2.33 MPa was obtained from the formulation with a 1:2 ratio of geopaste with transparent glass powder and fine sand. The measured strength corresponded to an apparent porosity of 6.30% and a water absorption of 4.50%. The bulk density was approximately 1.16 g/cm³, which is classified as a lightweight material. A prototype geopolymer concrete roof tile was successfully produced with a sorption coefficient of approximately 0.170 mm/min1/2. This measured sorption coefficient and the physical properties indicate that the produced roof tile is a potential building material.