The recycling of MDF fiber into wood-cement composites with carbon dioxide injection

摘要

The possibility of recycling medium density fiberboard (MDF) furnish into wood-cement composites was evaluated. Both virgin wood fiber and recycled MDF fiber had poor compatibility with cement if no treatment was applied. However, this problem was solved when a rapid hardening process with carbon dioxide injection was adopted. After 3-5 minutes of carbon dioxide injection, the composites reached 22-27% of total carbonation degree and developed 50-70% of their ultimate strength. Composites containing recycled MDF fiber had similar strength to those containing virgin wood fiber under appropriate production conditions, but had lower toughness values especially at higher fiber/cement ratio. Composites containing recycled MDF fiber also had lower water absorption amounts. There was a positive relationship between carbonation degree and strength of composites right after carbon dioxide injection but this relationship was not evident 28 days after carbon dioxide injection. Composites subjected to carbon dioxide injection showed better physical and mechanical properties than those cured conventionally. Unlike composites cured conventionally, carbonated composites had higher strength and toughness with increased fiber content.