A study was undertaken on the green moisture content, basic density and shrinkage properties for the wood of five Ghanaian species: Alstonia boonei (Sinduro), Antrocaryon micraster (Aprokuma), Bombax buonopozense (Akata), Dialium aubrevillei (Duabankye) and Sterculia rhinopetala (Wawabima). The overall green moisture content of the wood species ranged from a low of 51-52% (for D. aubrevillei and A. micraster) to a high of 177% (for B. buonopozense), while the overall mean basic density of the wood species ranged from a low of 366 kg/m 3 (for B. buonopozense) to a high of 738 kg/m 3 (for A. micraster). Green moisture content appeared to be inversely proportional to the basic density with a correlation coefficient of-0.962. Mean total tangential shrinkage was medium (4.6-4.7%) in A. boonei and B. buonopozense, and very large (9.0-10.3%) in S. rhinopetala, D. aubrevillei and A. micraster. Mean partial tangential shrinkage were small (2.7%) in A. boonei and B. buonopozense, medium (5.0%) in S. rhinopetala and D. aubrevillei, and large (6.1%) in A. micraster. Mean total radial shrinkage was medium (3.6-3.9%) in B. buonopozense and A. boonei, large (4.4%) in S. rhinopetala, and very large (5.3-6.3%) in D. aubrevillei and A. micraster; and mean partial radial shrinkage was medium (2.0-2.5%) in A. boonei, B. buonopozense, D. aubrevillei and S. rhinopetala, and large in A. micraster (3.5%). Except for A. micraster (~ 0.65%) total longitudinal shrinkage was typically less than 0.4%.
Sixty trees of ten high density Lesser Used Species (LUS) of potential importance to bridge construction were extracted from four forest reserves-Bobiri, Pra-Anum, Nueng, and Subri River (in four different ecological zones). Logs from the trees were converted on a horizontal bandmill to 27 and 53 mm thick boards. Specimens were prepared from the green boards for the determination of the green moisture content, basic density, and dimensional shrinkage of each of the ten species: Celtis mildbraedii, Celtis zenkeri, Combretodendron africanum (Essia), Cynometra ananta (Ananta), Lophira alata (Kaku), Nauclea diderrichii (Kusia), Nesogordonia papaverifera (Danta), Piptadeniastrum africanum (Dahoma), Strombosia glaucescens (Afina), and Sterculia rhinopetala (Wawabima). Mean green moisture content was lowest in Kaku (45%) and highest in Celtis zenkeri (93%). Mean basic density was highest in Kaku (840 kg/m 3) and lowest in C. zenkeri (560 kg/m 3). Mean green moisture content and mean basic density of the species negatively correlated with a correlation coefficient of-0.87. Mean total tangential shrinkage varied from a low of 6.2% for Dahoma to a high of 9.9% for Kaku. Based on the mean tangential shrinkage from green to 12% moisture content the dimensional shrinkage of the species were classified as 'small' for Dahoma, Kusia, Ananta and Danta; 'medium' for Celtis mildbraedii, Afina, C. zenkeri, Essia and Kaku; and 'large' for Wawabima. Tangential to radial shrinkage (T/R) ratio was 'very low' in Kaku, 'low' (or fairly close to 1.5) in Danta, Afina, C. zenkeri and C. mildbraedii, 'pronounced' (> 1.5) in Ananta and Dahoma; and 'very pronounced' (>> 1.5) in Kusia, Wawabima and Essia. The pronounced differential shrinkage (≥ 1.5) in these woods is likely to cause wide splits, checks and distortions if precautions are not taken during the kiln drying of these heavy wood species. Total longitudinal shrinkage was excessive and exceeded the normal figure of 0.2% in all ten species, and was higher than the rare figure of 0.4% in Kaku and Ananta.
Logs from sixty trees of ten high density Lesser Used Species (LUS) of potential importance to bridge construction were extracted from four forest reserves -Bobiri, Pra-Anum, Nueng, and Subri River in four different ecological zones. The logs from the trees were converted on a horizontal bandmill to 27 and 53 mm thick boards. One-half of the boards were used in the green state and the other half air dried. Mechanical strength test specimens were prepared and tested in accordance with the British Standard BS 373:1957. The range of mean strength values in N/mm 2 in the 'green' [and dry] conditions for the ten wood species were as follows: -Modulus Hardness in kN: 3.5-11.3 [5.1-17.0]. The 10 species in decreasing order of strength was as follows: Lophira alata (Kaku) > Cynometra ananta (Ananta) > Strombosia glaucescens (Afina) > Celtis mildbraedii > Nauclea diderrichii (Kusia) ≥ Celtis zenkeri ≈ Piptadeniastrum africanum (Dahoma) > Nesogordonia papaverifera (Danta) > Combretodendron africanum (Essia) > Sterculia rhinopetala (Wawabima). Mean ratios of dry to 'green' MOR and MOE were 1.44 and 1.28. There was a good correlation (84.4~98.2%) between the Density (X) and the various mechanical strength values (Y). Regression equations in the form: Y = aX b were derived with R 2 values of 0.72-0.93.
The susceptibility to drying defects and development of appropriate drying schedules was undertaken for the wood of five Ghanaian lesser used wood species: Alstonia boonei (Sinduro), Antrocaryon micraster, (Aprokuma), Bombax buonopozens (Akata), Dialium aubrevillei (Duabankye) and Sterculia rhinopetala (Wawabima). Susceptibility to checking is severe in D. aubrevillei and A. micraster and mild in S. rhinopetala, A. boonei and B. buonopozense. D. aubrevillei is mildly susceptible to honeycombing and deformation, while A. micraster, S. rhinopetala, A. boonei and B. buonopozense are not susceptible. The following experimental dry kiln schedules for lumber of thickness up to 38mm corresponding to the FPL Madison schedules are proposed: D.
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