Fire performance of heritage and contemporary timber encapsulation materials

Fire performance of heritage and contemporary timber encapsulation materials

Cultural heritage buildings are often recognized for holding significant heritage value; however, too often these structures are lost to fire. Timber is a building material commonly found in cultural heritage buildings, and for centuries encapsulations have been used in an attempt to improve the fire performance of timber. This research examines the history and evolution of encapsulating timber to improve its fire performance, through analysis of archival literature dating to over 200 years ago, as well as by, for the first time, evaluating the fire performance of bench scale samples of these historic and reproduced encapsulations with controlled and repeatable fire testing. The purpose of the tests is to truly understand successes and failures of these protective measures and to assist architects and engineers who may encounter these dated protective coating measures on timber. Plasters, metal plates, lime-based paints, and gypsum boards were all tested using a Cone Calorimeter apparatus, following an adaptive ASTM E1354 procedure. Heat release, material decomposition, charring, and ignition of timber were all analysed. Results show that plasters and gypsum board performed similarly, although historic plasters did not stay attached to the wood substrate post-testing, making them impractical for building applications. The iron plate still allowed heat transfer into the timber, provoking measurable char depth. Finally, the lime-based paint delayed timber ignition by only 20 s. These results indicate that none of the historic encapsulations significantly improved fire performance, and they therefore cannot be relied upon for fire protection if they are found in a heritage structure. While such encapsulations may still need to be left in-place from a heritage conservation perspective, other passive and active strategies might need to be implemented into the structure to ensure its fire performance and enable its successful conservation.

文化遗产建筑通常因其具有重要的遗产价值而受到认可；然而，这些建筑结构常常毁于火灾。木材是文化遗产建筑中常见的建筑材料，几个世纪以来，人们一直使用封装技术来试图提高木材的防火性能。本研究通过分析200多年前的档案文献，并首次通过可控且可重复的防火测试来评估这些历史上的以及复制的封装材料的小尺寸样本的防火性能，从而研究了封装木材以提高其防火性能的历史和演变。测试的目的是真正了解这些保护措施的成败，以帮助可能在木材上遇到这些陈旧的保护涂层措施的建筑师和工程师。按照经过调整的ASTM E1354程序，使用锥形量热仪对灰泥、金属板、石灰基涂料和石膏板都进行了测试。对热量释放、材料分解、炭化以及木材的着火情况都进行了分析。结果表明，灰泥和石膏板的性能相似，尽管历史上的灰泥在测试后未能附着在木材基材上，这使得它们在建筑应用中不实用。铁板仍然允许热量传递到木材中，导致可测量的炭化深度。最后，石灰基涂料仅将木材的着火时间延迟了20秒。这些结果表明，历史上的封装材料都没有显著提高防火性能，因此，如果在遗产建筑中发现它们，不能依靠它们来进行防火保护。虽然从遗产保护的角度来看，这些封装材料可能仍然需要保留在原地，但可能需要在建筑结构中实施其他被动和主动的策略，以确保其防火性能并使其能够成功得到保护。