Alkali-activated mortars and concretes have been gaining increased attention due to their
potential for providing a more sustainable alternative to traditional ordinary Portland cement mixtures.
In addition, the inclusion of high volumes of recycled materials in these traditional mortars
and concretes has been shown to be particularly challenging. The compositions of the mixtures present
in this paper were designed to make use of a hybrid alkali-activation model, as they were
mostly composed of class F fly ash and calcium-rich precursors, namely, ordinary Portland cement
and calcium hydroxide. Moreover, the viability of the addition of fine milled glass wastes and fine
limestone powder, as a source of soluble silicates and as a filler, respectively, was also investigated.
The optimization criterium for the design of fly ash-based alkali-activated mortar compositions was
the maximization of both the compressive strength and environmental performance of the mortars.
With this objective, two stages of optimization were conceived: one in which the inclusion of secondary
precursors in ambient-cured mortar samples was implemented and, simultaneously, in
which the compositions were tested for the determination of short-term compressive strength and
another phase containing a deeper study on the effects of the addition of glass wastes on the compressive
strength of mortar samples cured for 24 h at 80 °C and tested up to 28 days of curing.
Furthermore, in both stages, the effects (on the compressive strength) of the inclusion of construction
and demolition recycled aggregates were also investigated. The results show that a heat-cured
fly ash-based mortar containing a 1% glass powder content (in relation to the binder weight) and a
10% replacement of natural aggregate for CDRA may display as much as a 28-day compressive
strength of 31.4 MPa.