Greenhouse gas emissions is one of the most concerning issues in today’s world. Production of cement contributes to a significant amount of carbon dioxide (CO2) released to the atmosphere world-wide. Again, many of the industrial/agricultural wastes, often containing higher percentages of alumino-silicates, are contributing to issues concerned with environmental pollution. As a possible solution to these problems, this study attempts developing a class of one-part alkali-activated concrete (OPAAC) mixes, using a combination of fly ash and ground granulated blast furnace slag (GGBS) as a complete replacement to ordinary Portland cement. To optimize the mix-proportions of this class of concrete mixes, with minimum experimental effort, Taguchi’s design of experiments (DOE) approach is applied. Herein, total binder content, ratio of fly ash to GGBS (by volume), and percentage of sodium oxide in the mix are used as primary variables. Based on a L-9 orthogonal array of these parameters, identified at three levels, an initial set of nine OPAAC mixes are considered. Fresh and hardened properties of these nine OPAAC mixes are evaluated experimentally. The strength properties of the OPAAC mixes evaluated include—compressive strengths, split tensile strengths and flexural strengths. Based on the experimental results, linear regression equations are developed for the strengths. Further three additional verification mixes are also experimented on. The experimentally found strength characteristics of the verification mixes compare well with the results predicted based on linear regression equations. The results of this study also suggest that these mixes can contribute to sustainability in concrete industry.