Strengthening of archaeological wood using electroosmosis

Hundreds of waterlogged archaeological wooden pillars were discovered during the 2004 excavation of an archaeological site in Tianluo-Mountain, Zhejiang Province, China. These archaeological wooden pillars are invaluable cultural relics but are on the verge of decay and cracking due to the combination of a humid environment and bacterial surface erosion. Inspired by the stable silicified wood in the natural world, it was decided to silicify these fragile wooden pillars in situ to protect them. Wood was first treated in sodium silicate solution using electroosmosis technology, and then CaSiO3 precipitations were formed by immersing silicified wood in calcium nitrate solution to fix silicate in the wood. The wood microstructure before and after treatment was observed using scanning electron microscopy. It could be seen that particles were widely distributed throughout the internal part after treatment, while there were no particles present before treatment. EDS results showed that the particles are comprised mainly of silicon, calcium and oxygen, so it could be confirmed that calcium silicate was formed in the wood. Mechanical property tests indicated that the silicification process improved the axial compressive strength by 143%. Thus, archaeological wood has successfully silicified and the objective of strengthening has been achieved.