Calcarenite-Derived Lime Mortars Without Externally Added Aggregate: Experimental Validation and Implications for Historical Construction Technologies

Conventional lime mortars are commonly described as composite systems based on the functional separation between binder and aggregate. However, some historical mortars show microstructural features suggesting that both functions may derive from a single heterogeneous raw material. The experimental contribution of this study is the controlled production and testing of a reference mortar in which Panchina calcarenite is the sole solid precursor, supplying both the lime-forming and granular fractions without externally added aggregate. The calcarenite was investigated as a single natural source of both binder-forming and granular constituents: its carbonate fraction provides the precursor for lime formation, whereas its pre-existing siliciclastic fraction is retained as an internally derived granular component. A reference mortar was prepared exclusively from the calcarenite-derived material, while additional formulations contained 5–15 wt.% diatomaceous earth as a reactive siliceous addition. Mineralogical evolution, carbonation behaviour, hardened-state physical properties, and mechanical performance of the mortars were investigated after 12 months of curing. Compressive strengths of 2.0–3.3 MPa were obtained, depending on composition, supporting the technological feasibility of producing mechanically viable mortars without the separate addition of an external aggregate. The results support the feasibility of calcarenite-derived mortar systems in which the same heterogeneous raw material supplies both the binder-forming and internally derived granular fractions, and provide an experimental basis for discussing analogous technological solutions in historical construction.