Uncertainty analysis in the estimation of construction and demolition wastes emissivity through infrared thermography

Construction and demolition wastes (CDWs) represent one of the largest slices of global waste and can be a significant source of reusable materials in the context of sustainable and circular construction practices. The accurate characterization of these materials can be critical to improve recycling and valorisation processes. In this study, a measurement procedure is proposed for the characterization of CDWs using active infrared thermography to estimate the emissivity of the materials commonly used in this context. The material classes analysed are concrete, bricks, tiles and ceramic, wood, plastic, metals, paper and cardboard, and mixed CDWs. An experimental test protocol is defined for heating specimens and acquiring thermal images, allowing the accurate estimation of their emissivity based on a paint and a tape with known emissivity used as reference. To ensure the reliability and robustness of the estimated emissivity values, an uncertainty analysis is performed using a Monte Carlo simulation evaluating the impact of the uncertainty (u(xi)) related to the known emissivity value of the reference paint (0.89 ± 0.01, reported as mean ± standard deviation) on the results. The results show that the input uncertainty propagates along the measurement chain, leading to an output uncertainty (ui(y)) at least doubled for all classes, and more than doubled for the plastic class.