Waste marble dust was used to prepare epoxy composites. A detailed characterization of the waste marble dust indicated that it was constituted by calcium carbonate with only traces of dolomite and quartz and the mean particle size was lower than 10 μm. The effect of the addition of low amounts (from 1% to 8% by weight) of the powder on mechanical, morphological, and thermal properties of epoxy composites has been investigated. Environmental electronic scanning microscopy micrographs indicated that the waste marble dust, even if not organically modified, was homogeneously dispersed in the matrix. Thermogravimetric analysis showed that thermal stability slightly increased with the filler amount. The waste marble dust showed a mean particle size of 4.36 ± 0.43 μm and a high purity with over 99% calcite content. The composites exhibited enhanced thermal stability, with the residue at 900°C increasing proportionally with filler content up to 7.5 wt% for the highest loading, while tensile strength showed a slight increase at 3% filler but decreased at higher amounts. The findings show that the behavior agrees with that observed in the cases of addition of small amounts of inorganic nanoparticles, such as clays or nanomicas to epoxy resins indicating that waste marble dust with micro-sized particles can be used to modulate the properties of the final epoxy composite.
