Timber from Historical Foundation Piles Made of Oak Wood (Quercus robur L.)

Oak wood is a popular construction material in Europe. In the course of its service life, this wood is subject to structural changes resulting from the environmental conditions to which it is exposed, in addition to the effects of aging. Samples of naturally occurring historic European oak (Quercus robur L.) were obtained from foundation piles that were utilized to reinforce the riverbanks in Poland, the Vistula River basin, dating to the 2nd century, as well as from a 14th-century settlement on the river in Slupsk. Reference wood was also obtained from contemporary harvesting operations in the vicinity of Slupsk, Poland. The presence of structural changes resulting from partial wood degradation was confirmed through the utilization of FTIR spectroscopy analysis, SEM with BSD microscopy, and chromatic parameters. The differences in the color of historic and reference wood were significant (based on Kruskal–Wallis test = 46.38, where p < 0.001). The results of chemical analysis showed an increase in the proportion of lignin and a decrease in carbohydrate components for the old wood. A higher degree of change in lignin content was observed in historic wood (32–38%) compared to the fresh wood sample (25%). Our study showed that the collected data can be applied to the preparation database of heritage wood materials.