Definition of a condition-based model for natural stone claddings

Abstract

Nowadays, the degradation of the built environment is becoming a serious economic, cultural and environmental problem in several developed countries, after several decades of adopting an attitude of “built and let decay”. The lack of maintenance policies led to additional costs and risks for owners and increased the aesthetic degradation of our cities. In this study, a condition-based maintenance model, based on Petri nets, is used to analyse the influence of alternative maintenance strategies on the overall degradation of natural stone claddings. For this purpose, three maintenance strategies are considered: i) total replacement; ii) combination of minor intervention and total replacement; and iii) combination of cleaning operations, minor intervention and total replacement. The impact of the alternative maintenance strategies on the future performance and remaining service life of natural stone claddings is discussed. In this study, a sample of 203 natural stone claddings, located in Portugal, is analysed and the degradation of these claddings in-service condition is evaluated through in-situ inspections. Furthermore, a simplified multi-criteria analysis is carried out to evaluate the economic impact of each maintenance strategy in comparison with the increased durability achieved through its adoption. The results reveal that the adoption of other maintenance activities (minor interventions or cleaning operations) increases the operational costs, as expected, but promotes the durability of the claddings. The adoption of maintenance actions allows increasing the predicted service life of NSC (148 years for MS2 and 177 years for MS3), when compared with NSC that are not subjected to any kind of preventive maintenance (70 years).