The Correlation between Bulk Density and Shock Resistance of Waterlogged Archaeological Wood using the Pilodyn

Abstract

The correlation (R2 = 0.87) between bulk density and the shock resistance of homogeneously and heterogeneously degraded waterlogged archaeological wood, with densities ranging from 100 to 700 kg·m-3, was determined using the Pilodyn wood tester. The results showed that the energy required to fracture a given mass of wood substance was constant (R2 = 0.83) and independent of wood species. However, measurements in the three main orientations (longitudinal, radial and tangential) showed a significant variation and therefore further measurements were preferentially taken in the radial axis. A model to enable the determination of the average bulk density of waterlogged wood from the depth of penetration of the Pilodyn showed that the average bulk density of homogeneously and heterogeneously degraded waterlogged wood could be determined with an average accuracy of ± 9%. A high correlation coefficient (R2 = 0.995) for measurements taken in water and air enable the Pilodyn to assess waterlogged wood under water as well as in air.