Due environmental problems related to Portland cement consumption, many studies have been
performed to diminish its use. One solution is the development of alkali-activated binders, which can
decrease CO2 emissions and energy consumption by 70% when compared to Portland cement production.
In addition, an alkali-activated binder presents mechanical properties similar to Portland cement mix-
tures, which turns into an interesting material in civil construction. Aluminosilicate-based materials
are important raw materials to produce the alkali-activated binders. Therefore, two residues are pre-
sented as an aluminosilicate source in this study: fly ash (FA) and sugarcane bagasse ash (SCBA). Both
residues were obtained from a combustion process to generate energy, the former from coal and the
latter from the bagasse of the sugarcane industry. In addition, the alkaline activating solution is an impor-
tant factor to achieve improved mechanical properties. In this context, this study investigated the influ-
ence of four different SiO2/K2O molar ratios (0, 0.36, 0.75 and 1.22) in the activating solution with a
constant water content, and three FA/SCBA binder proportions (75/25, 50/50 and 25/75).
Microstructural characterization was carried out by X-ray diffraction, Fourier transform infrared spec-
troscopy, thermogravimetric analysis, scanning electron microscopy, mercury intrusion porosimetry,
pH and electrical conductivity measurements to study the evolution of the reaction process. The com-
pressive strength of mortars was assessed in order to determine the optimum SiO2/K2O molar ratio
and FA/SCBA ratio. The tests showed that a SiO2/K2O molar ratio of 0.75 and FA/SCBA proportion of
75/25 provided the best mechanical properties.