The use of powdered olive stone in lime-based mortars for the conservation of cultural heritage: A performance evaluation

This research paper investigates the use of Powdered Olive Stone (POS), an agricultural by-product, as a partial replacement for quartz sand in lime-based mortars used for the repair and conservation of historical structures. POS offers a potential solution, addressing waste disposal and reducing reliance on traditional aggregates. This study specifically focuses on lime-based mortars, one of the most commonly used materials in heritage conservation, addressing a research gap regarding the use of POS in this context. In particular, different mortar formulations were prepared by partially replacing natural quartz aggregates with POS at substitution rates of 5 %, 10 %, and 15 %. Additionally, the effect of nano-silica incorporation was evaluated. Following curing, the specimens underwent a comprehensive set of analyses, to examine both mechanical and physical properties of the produced mortars at 28 and 90 days of curing. Such investigations include colorimetric assessment, optical and electron microscopy analyses, capillary water absorption test, ultrasonic pulse velocity measurements, bulk density determination, salt crystallization resistance, and mechanical testing for compressive and flexural strength. demonstrate that the incorporation of POS resulted in significant modifications of both physical and mechanical properties of the mortars, which can be tailored in order to meet specific requirements of conservation projects. • POS darkens mortars and shifts color toward red-yellow due to its natural hue. • POS increases porosity, enhancing water and salt absorption for sacrificial action. • Nanosilica lowers water absorption and improves salt resistance in early cycles. • POS reduces density and strength; nanosilica only partially restores bulk density. • POS-SL mortars show poor strength due to ITZ issues and nanosilica agglomeration.