Learning from romans: when Vitruvian recipes became the inspiration for new technology

Aquileia is one of the most prosperous cities of the Roman Empire, where the abundance of materials and the exceptional craftsmanship converged to create exquisite decorative artefacts, such as floor mosaics. As reported by Vitruvius [1], Roman mosaics are constructed using a multi-layered system consisting of five different strata. This multi-layer structure, with high material heterogeneity within each stratum, poses a significant challenge for restorers. Traditional restoration methods involve the use of pastes to address damage in mosaic systems, including the consolidation of different strata e.g., grouting, filling of cracks and repositioning lost tesserae [2]. However, contemporary pastes utilized are predominantly hydraulic or non hydraulic lime mortars mixed with acrylic emulsions [3] and evenly cements. These pastes, while widely employed, are not specifically tailored for mosaic preservation. They often lack compatibility with the host material, resulting in only partial substrate repair and leading to secondary degradation effects. Compatibility is the key parameter to consider for the definition of the materials to use for restoration treatment [4]. This research centers on the development of novel mortar formulations intended for use in mosaic preservation. Their design is based on the results achieved by the analysis of mortars of Roman mosaics fragments and inspired by ancient recipes. The current trend toward greener and more sustainable building materials, has led to the renewed interest in using plant products as additives, drawing inspiration from antique solutions [5]. Therefore, we combine elements of mimesis and innovation of ancient technology, by introducing novel additives such as natural gel into the ancient formulations, based on both literature records and characterization of archaeological pieces. The chemical composition of both the ancient materials and the formulated ones, was characterized through X-ray diffraction (XRD) and scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) analysis, confirming their complete compatibility. Microstructural features were evaluated using microscopic and colorimetric analyses. The performances of the prepared mortars were assessed through slump test and rheological test of mortar at the fresh state. Additionally, analyses of compressive and flexural strength, water absorption tests, and evaluation of the surface hardness of hardened mortars at different curing times, were conducted. Primary results show the enhancement of workability thanks to the use of natural gel, minimal colorimetric change, modification of strength and water absorption induced by additives. These findings not only extend a warm invitation to delve into ancient techniques for discovering innovative functional products, but also align with the current trend toward environmentally friendly and sustainable building materials.