Compressive Strength of Cylindrical Samples as An Indicator of Wood-Cement Compatibility

Compatibility of wood-cement mixtures proposed by early studies was expressed as an inhibitory index, which was derived from hydration temperature and/or hydration time. Sometimes this index does not reflect the actual compatibility. A simple compression test of cylindrical samples made with the ASTM standard mold is presented here as an indicator of wood-cement compatibility. Compression samples were made with Type I portland cement and wood particles from each of the following species: southern pine, white oak, red oak, yellow-poplar, sweetgum, and hickory. Results indicate that compressive strength is linearly proportional to the maximum hydration temperature, but independent of hydration time. Without the influence of calcium chloride, compatibility of different species with cement can be indicated by the compressive strength or maximum hydration temperature. Adding calcium chloride (3 percent based on cement weight) to the mixtures greatly increases the maximum hydration temperature and compressive strength, and reduces hydration time. Results also indicate that the use of calcium chloride and a high cement/wood ratio (such as 13/1) makes it very difficult to distinguish compatibility among species.

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