Strength, Toughness and Durability of Extruded Cement Boards with Unbleached Kraft Pulp

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Title: Strength, Toughness and Durability of Extruded Cement Boards with Unbleached Kraft Pulp

Author(s): Y. Shao and S. Moras

Publication: Special Publication

Volume: 206

Issue:

Appears on pages(s): 439-452

Keywords: age effect, anisotropy, extrusion, fiber-cement board, freeze thaw cycling, hardwood pulp, natural weathering, softwood pulp

Date: 4/1/2002

Abstract:
The use of extrusion technology for the production of cement boards with unbleached kraft pulps I sevaluated in this paper. Cement boards reinforced both by hardwood and softwood pulp of different percentages were fabricated using an auger type lab extruder. The moisture contnet, water absorption and density of all batches were measured. The flexural response of the cement boards was used to investigate the strength, the toughness, the anisotropy, the age effect and the resistance to natureal weathering as well as to freeze-thaw cycling. With a relative ease of manufacture and a much claener production, extrusion was found to be a suitable means for making cement boards with up to 8% pulp by weight. Higher pulp content increased the toughnessof the material but didn’t enhance the flexural strength appreciably due to a higher water content required for extrudability. Anisotropic behavior and age effect were observed. The extruded products exhibited good resistance to weathering and freeze-thaw cycling. Hardwood pulps, cheaper and more available than the softwood ones, were found to be more suibalbe for extrusion production in terms of extrudability, finished surface and long term mechanical properties.