The present investigation is focused on the implementation of alkaline activated fly ash as a total replacement of Portland cement in the manufacture of prefabricated tablets. The experimental program included the physico-chemical characterization of raw materials, finding the optimum alkaline activator/fly ash ratio and mechanical tests of compressive strength and rupture modulus. Additionally, a comparison of the carbon footprint of a batch of prefabricated tablets made from Portland cement mortar and fly ash was also performed. The activation of the fly ash was carried out by means of the combination of alkaline activators composed of NaOH and Na2SiO3. The results obtained showed that fly ash mortars have good mechanical properties and environmental viability in terms of carbon footprint. The fly ash can be used in the industry of prefabricated tablets as an option of lower environmental impact with optimal resistance to compression and rupture modulus.