Large-Scale Enclosure Fire Experiments Adopting CLT Slabs with Different Types of Polyurethane Adhesives: Genesis and Preliminary Findings

Abstract

This paper provides understanding of the fire performance of exposed cross-laminated-timber (CLT) in large enclosures. An office-type configuration has been represented by a 3.75 by 7.6 by 2.4 m high enclosure constructed of non-combustible blockwork walls, with a large opening on one long face. Three experiments are described in which propane-fuelled burners created a line fire that impinged on different ceiling types. The first experiment had a non-combustible ceiling lining in which the burners were set to provide flames that extended approximately halfway along the underside of the ceiling. Two further experiments used exposed 160 mm thick (40-20-40-20-40 mm) loaded CLT panels with a standard polyurethane adhesive between lamella in one experiment and a modified polyurethane adhesive in the other. Measurements included radiative heat flux to the ceiling and the floor, temperatures within the depth of the CLT and the mass loss of the panels. Results show the initial peak rate of heat release with the exposed CLT was up to three times greater when compared with the non-combustible lining. As char formed, this stabilised at approximately one and a half times that of the non-combustible lining. Premature char fall-off (due to bond-line failure) was observed close to the burners in the CLT using standard polyurethane adhesive. However, both exposed CLT ceiling experiments underwent auto-extinction of flaming combustion once the burners were switched off.