In ancient times, how was wood preserved, such as the replacement of the pillars of those diaojiao buildings?

Ancient anti-corrosion mainly depends on materials and natural factors. For example, a large number of non-perishable Chinese fir are used in buildings, and then the Chinese fir are fully soaked in water for more than one year, so that the nutrients in the wood are precipitated and the degree and speed of decay are reduced.

I hope my answer can help you.