Evaluation of Salt-Induced Damage to Aged Wood of Historical Wooden Buildings.

Xiaochen Mi,Yongfeng Hu,Tieying Li,Jinping Wang

doi:10.1155/2020/8873713

Abstract

Salt is a common cause of damage to building materials used in cultural and historical buildings. The damage to aged wood in historical wooden buildings has not been extensively studied, resulting in the need for a more detailed analysis. In this work, Yingxian Wooden Pagoda, a typical historical wooden structure, was taken as the research object. Multichemical analyses were conducted to evaluate and understand the salt-induced damage to the aged wood using a scanning electron microscope equipped with an energy-dispersive X-ray spectrometer, sulphur K-edge X-ray absorption near-edge structure spectroscopy, X-ray fluorescence spectroscopy, X-ray powder diffraction, and attenuated total reflectance fourier transformed infrared spectroscopy. The results showed the presence of invasive salt crystallisations and ions in the aged samples. The source of these invasive elements was deduced by identifying the type, amount, and valency of the elements; they were found to be derived from environmental factors such as acid rain and atmospheric pollutant. The unique damage mechanism and route induced by salt in historical buildings made of wood were summarised; the damage was attributed to the accumulation of sulphate salt causing hydrolysis of the carbohydrates and salt crystallisation resulting in mechanical damage. This interdisciplinary study is significant for decision making in studies related to the preservation and evaluation of historical wooden buildings.

Highlights

The building materials of cultural buildings have undergone multifaceted damage including mechanical, environmental, and biological degradations
X-ray absorption near-edge structure (XANES) and X-ray fluorescence (XRF) measurements were performed at the Canadian Light Source (CLS) using the soft X-ray microcharacterisation beamline (SXRMB). e SXRMB is equipped with a Si (111) double-crystal monochromator with a resolving power of 10000. e powder sample was wrapped by a double-sided, conducting carbon tape and transferred to a vacuum chamber for measurements. e sulphur K-edge XANES spectra were recorded in the surface-sensitive total electron yield (TEY) by measuring the sample drain current and in the bulk-sensitive fluorescence yield (FLY) with an SDD detector
Multiple chemical characterisation methods were applied to evaluate the salt-induced damage of Yingxian Wooden Pagoda, a typical wooden historical architecture, including the nature and damage patterns. e following are the conclusions drawn from the study: (1) rough micromorphological observation, massive dense, granular materials were found in the aged wood samples. e EDS spectrum indicated that these materials contain inorganic elements, such as sulphur, calcium, sodium, and chlorine, consistent with the detection of some crystalline hydrated salts, such as gypsum and wollastonite, by X-ray powder diffraction (XRD). erefore, the presence of salts was confirmed in the aged wood of Yingxian Wooden Pagoda

Summary

Introduction

The building materials of cultural buildings have undergone multifaceted damage including mechanical, environmental, and biological degradations. Salt crystallisation is one of the sources of damage [1]. These types of damages are universal, the changes do not become obvious in a short time and are overlooked. Salt deterioration of ancient cultural buildings is an important issue worldwide. Is is because of the intrusive characteristics of salt and its influence on structural components, threatening the sustainable preservation of our valuable cultural heritage buildings. Salt gets deposited in the pores of building materials exposed to the natural environment [2]. E numerous salt crystals formed in the pores through phase change can lead to an increase in the elastic limit of the material [3]. The materials undergo severe damage such as discoloration and deposition, flaking, loss of material, and even material disaggregation [4]. ese damages are mostly induced at the structural cross sections and gradually migrate inward from the surface, leading to a decrease in the load and deformation capacity of the overall structure and affecting the stability

Methods

Results

Conclusion