Investigating the Effects of H₂O Interaction with Aluminium Composite Material Rainscreen Cladding Panels during High-rise Façade Fires

Abstract

Hypotheses stipulating that adverse exothermic reduction-oxidation (redox) reactions between aluminium-alloy sheets, used as facings for aluminium composite material (ACM) rainscreen panels, and water vapour (2Al + 3H2O → Al2O3 + 3H2), contribute to the severity and rate of fire spread during high-rise façade fire events, including the fatal Grenfell Tower incident on 14 June 2017 in London, United Kingdom (U.K.), have circulated amongst both industry and academia in the recent years since the disaster. With a lack of direct research and quantitative evidence available to either conclusively support or refute these claims, an ad-hoc investigation was undertaken providing insight into the significance of such reactions, and the likelihood of occurrence, in the context of a façade fire scenario comprising ACMs. Two common ACM panel variants (a polyolefin blend-based core product, PE, and a fire-retardant version, FR) were characterised, analysed to derive material-specific kinetics, and subjected to a series of bench-scale fire performance testing, involving the use of a cone calorimeter with an in-situ application of liquid-mist and water droplet sprays. Formulated inverse stoichiometric analyses of the experimental smoke yields, with respect to O2 consumption measurements, were used to identify anomalies in fuel composition following H2O application, given that H2 combustion does not produce CO2, in contrast to hydrocarbon fuel (CxHy) content within combustible ACM core products. This was achieved using controlled mist spray experimentation, specifically designed for the relevant research objectives. Contemporary numerical modeling techniques adopting computational fluid dynamics were also applied, providing additional insight through a constructed inverse modeling framework, and innovative coupled pyrolysis-combustion simulations, with two-way verification-validation of experimental-simulation data. From the work undertaken, the evidence compiled indicates insufficient quantities of H2 are produced by Al-H2O reactions at the conditions attained by ACMs during façade fire events. Consequently, the findings strongly oppose hypotheses of Al-H2O reactivity contributing to the combustion of ACM façade components and reaffirms the use of water as an appropriate extinguishing agent on aluminium-based façade components; No significant risk to fire spread or severity is anticipated through aluminium-water reactivity. ACM samples with ~30 wt. % polymer content (FR) demonstrated an average 73% reduction in pHRR, and 65% reduction in THR, in comparison to samples containing ~70 wt. % polymer (PE). ACM cladding panels with a low polymer content (≤10 wt. %) that achieve EN A2-s1,d0 classification are considered safe for use in high-rise façade assemblies.

Date of Award	2 Feb 2023
Original language	English
Awarding Institution	University of Portsmouth
Supervisor	Sarinova Simandjuntak (Supervisor), Jurgita Zekonyte (Supervisor) & James Buick (Supervisor)