Towards Standardised Strength Assessment: Protocol Development for Reused Glass

Protocol Development for Reused Glass

Abstract

The reuse of architectural glass is a key pathway towards circular construction, yet the absence of standardised procedures for disassembly, specimen preparation, and mechanical characterisation of post-consumer glass limits comparability across studies in absence of a standardised procedure. We investigated current testing and evaluation procedures and reproduced the full process chain –  from deconstruction of insulating glass units and structured specimen preparation with cleaning and surface inspection, to comparative mechanical testing using coaxial double-ring (CDR) test rig. As an update on ongoing research, we provide contributions to developing a harmonised approach by comparing existing methods and investigating a statistical evaluation that allows for uniform comparable strength values over different populations and procedures. Therefore, failure stresses are evaluated following ASTM C1499 and EN 1288 and transformed via time-equivalent and effective-area corrections employing normal, lognormal- and Weibull distributions. This study explicitly investigates the suitability of CDR testing for naturally aged glass – with two configurations of support and load radii, as well as two load rates. Accordingly, effects of parameter choice on derived stresses and goodness-of-fit metrics are quantified. Specimens were extracted from two façades located in Munich, Germany. Results, used as a basis for underlining the need for further discussion in the community, reveal systematic differences attributable to choices of geometry, load rates, and calculation methods. They show that loading configuration and calculation approaches strongly modulate derivable bending strengths. The resulting workflow—from deconstruction to probabilistic evaluation—supports the continuing discussion on harmonised strength assessment of naturally aged glass and provides an evidential basis for ongoing standardisation to enable circular use of architectural glass.