Evolved factor method for service life prediction of building components

Key issues in the production process associated with construction are the implementation of quality and sustainability principles. Indeed, it is increasingly important in the maintenance of quality levels provided by materials, components and building structures, especially after the recent Regulation (EU) No. 305/2011. This document introduced the seventh requirement for the sustainable use of natural resources, guaranteeing the durability of construction products, thus being planned. The international standard for the assessment of durability of building materials and components is the ISO 15686 - Buildings and constructed assets - Service life planning, providing the definition of the Reference Service Life (RSL) and identifying the procedures for the estimation of the Estimated Service Life (ESL), by means of three possible approaches: factor method, engineering methods and stochastic methods. The factor method (ISO 15686-8:2008) is the easiest to implement, but it suffers from a high subjectivity, possibly limited by the use of suitable performance grids, specific for each building component. This work is part of branch of research, suggesting an evolution of the method in semi-probabilistic way, well-known as "evolved factor method", based on the substitution to each deterministic value of the factor, proposed by the ISO, with a probability distribution function, in order to achieve a probability distribution function of the ESL. In particular, it is proposed to replace the multiplicity of functions with the use of the log-normal distribution function, as appropriate to model the phenomena where the random variables are multiplied with each other, simplifying the calculation of the ESL. The proposed solution was validated by the application to the example in the ISO 15686-1:2000, leading to consistent results with those of the standard and those of other similar reported studies, based on modifying solutions of the evolved factor method.