The aim of the study was to compare the modulus of elasticity (MOE) and modulus of rupture (MOR) of untreated and preservative impregnated small diameter Scots pine (Pinus sylvestris) fencing posts in static bending test. Butt logs originating from young and advanced thinning stands were turned to the nominal diameter of 120 mm and cross cut to the length of 2350 mm. The impregnation treatments were pressure impregnation to AB class and pine oil impregnation. After the relatively mild four-week-long weather chamber test, the posts were stored in room temperature until acoustic and destructive bending tests. The acoustic velocity was measured with Director HM200 tool. Dynamic MOE of the test posts was calculated based on the acoustic velocity and wood density, and compared with the bending MOE and MOR values obtained from the static bending tests (EN 408:2003). In calculations, the MC’s of the posts were adjusted to correspond to 12%. The untreated posts had the highest acoustic velocity, 4.9 km/s. The acoustic velocity did not differ between the pressure impregnated and pine oil impregnated posts, being 4.6 km/s in both groups. Linear regression analysis showed a significant relationship between the static and dynamic MOE for the entire data (r2: 0.78), the r2 values for different treatment groups varying from 0.40 to 0.91. Linear regression analysis between the MOR and dynamic MOE resulted in r2 values from 0.01 to 0.74. Regarding the dependence on wood density, the r2 values of 0.00-0.87 and 0.07-0.74 were obtained for the static MOE and MOR, respectively. In all cases, the untreated posts showed higher r2 values than pressure impregnated or pine oil impregnated posts. To conclude, chemical modification of wood appears to decrease its acoustic velocity. However, the acoustic velocity seems to be an applicable method to predict the bending MOE of both untreated and chemically modified posts.
Keywords: coustic measurement, Pine oil treatment, Pressure impregnation, Stifness, Strength
Authors
Möttönen V.
Finnish Forest Research Institute, Joensuu
Heräjärvi H.
Finnish Forest Research Institute, Joensuu
Stöd R.
Finnish Forest Research Institute, Joensuu
Koivunen H.
Finnish Forest Research Institute, Joensuu
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