Properties of clear wood and structural timber of Pinus halepensis from north-eastern Spain
The Aleppo Pine (Pinus halepensis) is a tree species spread all around the Mediterranean basin including the islands. Its continental range extends from northern Africa (Morocco, Algeria, Tunisia and Libya) and Middle East (Syria, Lebanon, Jordan, Palestina and Turkey), up to southern Mediterranean Europe (eastern Greece, Croatia, northern Italy, eastern France and eastern Spain).
It grows mostly from sea level to 1.000 m. In Spain is most abundant from 200 m to 600 m because lower altitudes are occupied by crops or urbanized areas. In meridional latitudes can be found even at 1.600 m. The Aleppo Pine usually prefers poor carbonated soils but can also live on chalky ones. It bears semiarid climate with dry and hot summers, cold winters and large annual thermal range. The species needs an average annual rainfall of 350-700 mm but can survive with only 200-300 mm.
It is a xerophilous and heliofilous species with little and irregular annual growth. The biggest trees may reach 50 cm of diameter and 20 m height but they usually don’t get over 40 cm and 15 m. The stem it is not very straight, large branches are common, therefore has low quality. It has an average growth of 2.4 m3/ha/yr (Burriel et al. 2000-2004).
For all these reasons, the Aleppo Pine nowadays in Spain it is mainly being used by the packaging industry for producing pallets. However, traditionally round trunks were used as beams in isolated houses located nearby the forests, especially in the Mediterranean coast where it is the most abundant tree. The goal of the study was to characterize the physical, mechanical and structural properties for knowing the potential of the Aleppopine for building.
MATERIALS AND METHODS
The study is divided in two: characterization of clear wood and characterization of structural timber. The timber used in the experiment came from two locations in Catalonia (North-easternSpain). Both locations belong to the region of provenance “Catalunya interior” as defined by Gil et al. (1996).
Clear wood test samples were made according to UNE 56528:1978 (AENOR, 1978) and afterwards conditioned at 20ºC and 65% of relative air humidity until they reached 12% of moisture content. All the clear wood specimens were extracted from the rejected beams from “Serra de Prades”. 146 specimens were tested on each of the six properties analyzed on an Incotecnic MUTC-200.
100 beams were from the “Serra de Prades” (Tarragona) and they had nominal dimensions of 50×150×2850 mm. There were other 81 smaller beams from “Prats de Lluçanes” (Barcelona) with nominal dimensions of 45×110×2000 mm. Prior to the visual grading, the beams were kiln dried up to the 12% of moisture to avoid dimensional changes, deformations or fungal attacks.
68 beams of Aleppo Pine from “Serra de Prades” and “El Lluçanès” were accepted after being visually graded according to the criteria of UNE-EN14081-1:2006+A1 and UNE 56544:2007. The bending tests were done on a Hoytom CM-DF 300/A1500 according to UNE-EN 408:2011. The experiment design and the characteristic values calculation followed the norm UNE-EN 384:2010 and the strength class was assigned in agreement of the UNE-EN 338:2010 standard.
RESULTS
Clear wood properties
The results are shown on table 2.
Mechanical characterization
The 77% of the beams were rejected on the grading. All the 100 beams of the batch of “Serra de Prades” were rejected on the visual grading because of their low quality. Nevertheless 27 were also tested to check their resistance. However the 81 beams of the batch of “El Lluçanès” had better quality. Unfortunately there were very few ME-1 beams and only were tested 41 ME-2-like structural specimens.
Contrasting the three characteristic values it can be seen that the Aleppo Pine ME-2-like timber is relatively stiff and heavy comparing it with its loading capacity. The MOR is what limits the strength class to C14.
An special feature of the Aleppo Pine timber is the behaviour when breaking. The beams don’t crunch or crack much during the load because the timber is rigid, but the breakings are sudden and violent and all the energy is released at once. Most beams resulted seriously damaged when broke. This behaviour is probably due to the material can’t much cope with plastic strain.
The study reached three conclusions.
- The clear wood of Aleppo Pine has better resistance than other coniferous timber ofSpain. Unfortunately the timber has low quality and a lot of rejection. Thus, it is necessary to invest on silvicultural works.
- The Aleppo Pine from North-eastern Spain (Catalonia) is the native pine timber with the lowest load capacity. When visually graded as ME-2 class as defined on the UNE 56544:2007 it might be considered C14.
- Only one quality strength class should be purposed for this species if included on a visual grading norm.
Abstract of paper “Properties of clear wood and structural timber of pinus halepensis from north-easternspain” presented by Correal-Mòdol, E., INCAFUST’s researcher at World Conference on Timber Engineering.Auckland,New Zealand. 2012.
