Alkoxysilane-based consolidation treatments: Laboratory and 3-years In-Situ assessment tests on biocalcarenite stone from Roman Theatre (Cádiz)

[Display omitted] •Effective interactions between the products and the biocalcarenite are observed.•Incorporation of SiO2NPs enhances mechanical performance and curing time.•The products fulfill the compatibility requirements for cultural heritage buildings.•Treatment effectiveness in lab is consistent with the in situ evaluation.•Mechanical properties of Ostionera stone were improved after new products application. This manuscript presents a 1 year in the laboratory and 3 years In-Situ evaluation of an alkoxysilane-based consolidant containing SiO2 nanoparticles (SiO2NPs) on Ostionera stone, a biocalcarenite traditionally employed in Southwestern Spain. Cádiz Roman Theatre was selected for In-Situ application and testing. In order to safeguard the theatre, preliminary laboratory experiments were carried out. Firstly, the compatibility and the effectiveness of the consolidant product were evaluated in the laboratory, demonstrating that the incorporation of SiO2NPs improves drying time and consolidant effect. Subsequently, the consolidant was applied In-Situ and the long-term performance was monitored over 3 years through non-destructive tests. The treatment exhibit moderate incompatibility degree (6.1) and demonstrating the long-lasting performance of the SiO2NPs-based consolidant treatment.