Drying behavior and physico-mechanical properties of solid bamboo (Dendrocalamus strictus Ness.)

The kiln drying schedule as well as the air drying method used in this experiment was satisfactory for drying round solid bamboo without danger of occurrence of seasoning defects. It took only 79 hours to reduce the moisture content from green to final moisture content of 11.32% for scraped and 16.23% for unscraped, while those in air drying took 59 days to reach an average moisture content of 17.14% for scraped culms and 20.04% for unscraped culms. At the early stage, the drying rate was found relatively faster and became slower at the next stage up to the slowest drying rate at last stage. Scraped culms dried faster than unscraped. With a little bit of modification in temperature and EMC [equilibrium moisture content] during the last stage of drying, the drying time may probably be shortened with little or no drying defect. Scraping improved drying rate in kiln and air drying conditions but gave no significant effect on tangential shrinkage, specific gravity and mechanical properties. The butt portion showed the highest tangential shrinkage of 8.789% at the node and 12.948% at the internode of the air dried culms and 10.324% at the node and 15.455% at the internode of kiln dried culms. It was followed by the air-dried middle portion and the kiln dried middle portion. The lowest was air-dried top portion and kiln dried top portion. Specific gravity significantly increased from green condition to air dried and kiln-dried condition. The specific gravity was also found decreasing from the top toward the butt portion. The internode had higher specific gravity. All mechanical properties significantly increased from green to dried condition. Kiln dried culms definitely showed higher value in all strength properties than air-dried culms. Scraped kiln-dried culms were recorded to have the highest SPL [stress at proportional limit], MOR [modulus of rupture], MOE [modulus of elasticity] and MCS [maximum crushing strength]. It was followed by unscraped kiln dried, scraped and unscraped air-dried culms and the lowest is green condition. All the strength properties were also found decreasing from the top toward the butt portion