How the materials knowledge of Roman mortars could be helpful for the production of future materials. The case of the Aqua Traiana aqueduct (Rome, Italy)

Starting from the knowledge of ancient materials, the present work aims at developing green eco-friendly restoration mortars. A multi-step approach is proposed for this purpose including a characterization of ancient mortars, followed by that of the raw materials, ending with an in-depth one of the new products. Therefore, new mortars have been produced following the ancient recipe used in the construction of the Aqua Traiana aqueduct (Rome, 2nd century CE). Minero-petrographic and mechanical features, along with the assessment of porosity, water absorption, hydraulic index, and the evaluation of phytotoxicity toward microalgae cells, have been considered to evaluate the new products. The results proved that the nature of the aggregate and of the binder influence the porosity and the formation of newly reaction phases. The growth of these minerals creates a porous network inside the binder paste which shows an efficient reactivity in the formation of C-S-H compounds.