The mechanical behaviors that can occur under the influence of high temperature in the mortars produced by silica fume and waste marble dust were investigated in this study. For this purpose, Portland cement (CEM I), waste marble dust (MD) from Afyon cavdarlar Marble Factory, silica fume (SF) of ETI electrometallurgy INC. industrial waste, CEN standard sand and water were used in the production of mortar. Mechanical experiments such as high temperature effect and cooling process with some physical experiments were performed on MD, SF and SFMD. Blended cements were obtained by using MD, SF and SFMD at 5.0%, 10.0%, 15.0% and 20.0% ratio with substitution method in Portland cement. Density, Blaine, initial set and final set were performed on the produced mortars and 40x40x160 mm sized mortar prism samples were obtained using these cements. These samples were exposed to five temperature effects as 20, 150, 300, 700 and 900 degrees C. The mortar samples kept at 20 degrees C were accepted as reference mortar. A total of 1053 samples were studied in two different ways of cooling mortars as air-cooling (spontaneously at 20 degrees C +/- 2 in laboratory environment) and sprinkling (water spraying). After the mortar samples reached at room temperature, flexional resistance and compressive strength tests were carried out on 7th, 28th and 90th days. According to the test results; it was determined that MD, SF and SFMD can be used as pozzolanic additives in cement mortars both alone and together and can be evaluated in buildings with high probability of fire up to certain temperature values.