Material Characteristics and Residual Strength for Decay of Compressed Wood Made of Japanese Larch

Utilization of scrap wood produced by thinning-out the Japanese larch forest is a serious problem to be solved. Since wood is comparatively easily strengthened by compressing it, depending on the future developments, a lot of usages of compressed wood can be expected in the future. On the other hand, the decay of wood damages the timber and it remarkably shortens the life of a wooden building. In this study, the investigation was carried out to aim to apply compressed wood produced by compressive forming to wooden buildings. The following conclusions were obtained as the first stage. 1)The compressed wood was produced through four processes of softening → compression → shape fixation → drying. Particularly, the condition of shape fixation is steam processing at 132°C for 70 min. 2)As for a useful index to clarify the situation of compression, it was found that “late wood ratio” is even better than “density”. 3)The accelerated decay tests for compressed woods and non-compressed woods were conducted. Then, these decayed woods were subjected to a uniaxial compression loading. As a result, it was found that, after the decay test, the compressive Young's modulus and the compressive strength of compressed woods are larger than those of solid wood. In point of residual strength for decay durability, compressed wood is superior to solid wood(non-compressed wood).