Geopolymers are a new type of material offered as an alternative to traditional Portland cement. Geopolymers, produced by activation of natural and waste pozzolans with alkali activators such as NaOH (SH) and Na2O center dot 3SiO(2) (SS) solutions, have been widely supported and investigated due to environmental and economic advantages. In this study, a detailed experimental program was conducted to investigate the influence of activator type, activator concentration and curing temperature on mechanical and microstructural properties of volcanic tuff based geopolymer mortar (GPM) and concrete (GPC) samples. A total of 1080 GPM and GPC samples were produced and a number of parameters were investigated with 360 combinations. Maximum compressive strength was obtained as 37.09 MPa in 90-day samples in which the SH concentration was 16 M, activator/binder (a/b) ratio was 0.45 and the curing temperature was 120 degrees C. As a result of optimization of the production parameters, a considerable development in mechanical and microstructural properties of GPM and GPC samples was obtained. Experimental results demonstrated that alkali activation with sole SH bring about superior characteristics compared to alkali activation with SH + SS. Higher a/b ratio led to higher UPV values because of more dense and compact microstructure resulting from increase in gopolymerization reactions. This is also supported by compressive strength and microstructure findings. (C) 2019 Elsevier Ltd. All rights reserved.