This chapter reports the effects of high-volume waste ceramic powder (WCP) inclusion on the mechanical and microstructure properties of alkali-activated mortars (AAMs) exposed to elevated temperatures. Such ternary mixes were designed by blending the abandoned waste materials from Malaysian agro and construction industries including WCP, ground blast furnace slag (GBFS), and fly ash (FA) with low concentration of alkaline activators. The as-prepared mortar specimens were heated up to 900°C to determine their temperature-dependent residual compressive strength, weight loss, and microstructures. The deterioration of the AAMs at elevated temperatures was evaluated by X-ray diffraction (XRD) measurement, thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FESEM). The resistance of the proposed AAMs to elevated temperatures was enhanced with the increase WCP contents from 50 to 70%. Furthermore, the replacement of GBFS by FA in the ternary blends led to the reduction of the mortar deterioration up to 900°C.