Exploring the Influence of Heating Conditions in the Charring Profile of Bare Timber and Timber Protected With a Thin Intumescent Coating

Abstract

This research examines the influence of a thin intumescent coating applied on mass timber, focusing on how changes in the in-depth charring rate may occur during a fire event. An experimental fire methodology was used whereby the transient in-depth heating conditions were carefully measured during testing. The heating conditions at the exposed surface of each sample were controlled by keeping a constant incident radiant heat flux at the exposed surface of the sample, considering the transient swelling of the intumescent coating -employing the H-TRIS method. Test samples of (200×200) mm 2 were prepared from Cross Laminated Timber (CLT) with a depth of 110 mm. The mean measured DFT amongst the coated samples was 1.19 ± 0.10 mm. Fire experiments were conducted for bare and coated timber samples, with the heated surface exposed at three different heat fluxes of: 25, 50, 75 kW/m 2 . The outcomes of this experimental study demonstrated that timber protected with a thin intumescent coating shows a delayed onset of charring and reduced in-depth charring rate for all heating conditions examined. However, the coating underwent considerable thermal degradation and regression at higher heat fluxes. Additionally, the mean measured charring rate was directly proportional to the incident radiant heat flux.