Waste andesite dust (WAD) occurs during sawing and other stone dressing processes of andesite stone. The disposal of WAD may cause storage and environmental pollution problems. The use of WAD in geopolymer production may be a solution to these problems. The mechanical and microstructural properties of geopolymer mortars synthesized from WAD were investigated in this work. To investigate these properties, the geopolymer mortars were manufactured using WAD with different molarity variations of NaOH as alkali-activator. The produced fresh WAD-based geopolymer mortars were cured at 100 degrees C in three different periods (12, 24, and 48 h). The results revealed that the ultrasonic pulse velocity (Upv), flexural strength (ffs), compressive strength (fcs) of WAD-based geopolymer mortars increased as increasing NaOH molarity until reaching an optimum concentration (12 M for this work). Curing periods also significantly affected the mechanical and microstructural properties of WAD-based geopolymer mortars. The results showed that the higher ffs and fcs values can be obtained with a longer curing periods. Moreover, considering overall performance analysis, geopolymer synthesis with WAD promises a solution for sustainable mortar production and waste elimination. (c) 2021 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.