Wood-cement Composites Research Articles

Controlled Dimensional Variations of a Wood-Cement Composite

At present wood-cement composites are used in pressed panels and unpressed blocks. These elements present interesting physical, acoustic and mechanical properties as well as good manufacturing properties. However, dimensional variations with external humidity remain high and prevent external use of the composites without an additional treatment. Dimensional variations are linked with wood, the wood-matrix interface and the cement matrix. A specific treatment for each of these previous elements allows reduction of dimensional variations. However, these deformations still remain higher than the standard values measured under conditions fixed by the French standard i.e. 1 mm/m. On the other hand, an appropriate combination of the three treatments achieves the expected objective at a reasonable cost compared to the one obtained for a conventional cement-sand-gravel composite.

Investigations on the influence of the addition of carbon dioxide on the production and properties of rapidly set wood-cement composites

This paper gives a short description of the manufacturing process of cement particle boards. Production methods currently used are characterized by a pressing time of boards of about 8 h. Also, flakes from only a limited number of wood species are suitable as reinforcing material. A new process is described where pressing time is reduced to only 4 min, and which allows the utilization of wood species not known as suitable so far. This prcess is distinguished by the injection of carbon dioxide into the furnish during pressing, where-upon the cement sets within a few minutes. A similar process, also described in this paper, uses carbonates of ammonium, sodium or potassium as additives to the mixture of wood flakes, cement and water. The carbonates decompose during pressing and carbon dioxide is released to react with calcium hydroxide from the hydration process. Thus, the cement sets within a very short time. The paper compares the properties of cement particle boards made according to these new processes with those from the old process.

Mixed inorganic binder for wood cement composites

The mixed binder sets at ≤60°C within less than 8.5 min. Birch, poplar and larch do not inhibit the hardening. Glucose, and to a lesser extent tannin, act as accelerators.

木質セメント複合材の吸水特性

The characteristics of water absorption of wood-cement composites were investigated, comparing with those of particle board.The results obtained are as follows:(1) The water absorption of wood-cement composites was smaller than that of particle board. But up to about ten hours the water absorption of wood-cement composites was larger than that of particle board.(2) The coefficient of thickness swelling of wood-cement composites was 1/2∼1/3 of particle board. The reasons why that of wood-cement composites was small, are considered as follows: (1) The wood content of wood-cement composites is smaller than that of particle board. (2) The pressure intensity of pressing for making wood-cement composites is lower than that for making particle board. (3) On absorbing water, the recovering force of compressive strain in wood-cement composites is smaller than that of particle board, because the wood moisture content of wood-cement composites is high at the time of making them.(3) On absorbing water, the bond durability between wood and cement is a little smaller than that between wood and synthetic resin adhesive such as phenolic resin adhesive.