AbstractDifferent fine materials that constitute either industrial or mining by-products were incorporated as filler materials in self-compacting (SC) mortars, aiming at improving their sustainability. More specifically, two common by-products of the cement industry—cement kiln dust (CKD) and bypass dust (BPD)—were evaluated together with the fine content (PeP) of residuals of perlite mining (RoM) before and after further grinding or thermal treatment, yielding the fine material products μ-silica (MS) and expanded perlite (EP), respectively. The five by-products, two limestone fillers (MP20/80), and pumice were incorporated in SC mortars, for which the last two types served as reference fillers. The effect of all fillers on the rheology, strength, and hydration of the mortars was comparatively evaluated with respect to their nature, size, shape, and inherent pozzolanic reactivity. The results illustrated that all prepared mixtures achieved the rheological criteria of self-compaction, developing satisfactory strength and altered hydration heat. The examined by-products proved to be equivalent alternative fillers for SC mortars, increasing their sustainability, which is significantly burdened with the increased grinding needs of the limestone fillers.