Mechanical and durability-related properties of one-part alkali-activated slag mortars

The mechanical and durability-related properties of a one-part alkali-activated slag (AAS) were evaluated for use as a sustainable alternative to conventional clinker-based materials. The AAS formulation was activated with stoichiometric calcium hydroxide and sodium carbonate. Compressive strength, drying shrinkage and weight change were monitored up to 112 days under dry and saturated conditions, extending previous studies limited to compressive strength up to 28 days under dry curing. For the first time for this formulation, pull-off strength and thermal conductivity were measured at 114 days, and the effects of polycarboxylate ether (PCE), with and without microsilica (MS), were systematically investigated for all tests. The tested AAS formulations exhibited compressive strengths ranging from ∼8–20 MPa at 28 days, with the greatest improvements observed with the incorporation of PCE and MS (AASMS). These additives also mitigated the high sensitivity of AAS to storage conditions. Surface strength values, rarely reported in the literature, met the requirements for repair mortar applications, with the best performance in the AAS with MS. Thermal conductivity measurements revealed lower values compared with conventional cement mortars of similar density, suggesting advantages for thermal insulation. Overall, the findings confirm the potential of this AAS formulation as an eco-friendly building material, combining intermediate mechanical properties with favourable thermal performance.