Manufacture of Wood Strand―Cement Composite for Structural Use

摘要

A new composite composed of wood strands and a cement-based matrix named Cement Strand Slab (CSS), was developed and the influence of manufacturing conditions on its strength properties was examined. Wood strands were produced by splitting slabs of sugi (Cryptomeria japonica) using a roll press-slitter which was developed by the Forestry and Forest Products Research Institute. Wood strands were air-dried, dipped in water or cement solution, treated with water by pressure-vacuum or coated with paraffin. The wood strands were mixed with mortar (Portland cement, sand, water, calcium chloride) and aligned longitudinally in a steel mould. The mortar was cured under pressure at room temperature for 48 h. The slab was removed from the mould and cured for 2 to 6 months before being subjected to a bending test. The modulus of rupture (MOR) of CSS was 20―40 MPa and its modulus of elasticity (MOE) was 20―25 GPa. The strength properties of CSS are therefore sufficiently high for it to be used for structural members. It may also possess greater fire resistance than competing wood composite lumber substitutes because of its high cement content. The MOR was improved by treating wood strands with cement solution and it was also affected by the vacuum-pressure treatment of strands with water. From these results it may be inferred that contact between the wood and the cement is an important factor affecting the strength properties of the composite.