Bending creep of Maritime pine wood (Pinus pinaster Ait.) chemically modified

Abstract

The long-term performance of a st ructural member is determined by its durability and deformation with time. The bending creep behaviour of modified wood was assessed experimentally over a pe riod of 35 days (840 hours). Four chemical modification processes were used: 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU), mmethylated melamine formaldehyde resin (MMF), tetraethoxysilane (TEOS) and amid wax (WA). Wood stakes with 20 . 10 . 200 mm RTL dimensions of Portuguese Maritime pine (Pin us pinaster Ait.) from sapwood part of the stem were used for evaluated the primary creep. Experiments were conducted at bending stresses amounting to 0.1, 0.2, 0.4 of the mean immediate wood bending strength obtained at equilibrium moisture content (EMC). Applying the same stress level (SL, 0.2), wood creep was also determined at the constant low and high moisture content. As results: Between low and medium SL (8 and 16 N/mm 2 ), unmodified wood at indoors conditions did not show any effect in the creep factors (kc). However, at high SL (35 N/mm 2 ) a slight increase (not significant) in the k c was found. It seems that the kc was nearly independent of the SL. In the lumen fill modification (TEOS and wax), the deposited material has not affected the creep behaviour under various SL.