Improving the accuracy of wood moisture content estimation in four European softwoods from Spain

Aim of study: To obtain improved models to predict, with an error of less than ± 2.0%, the gravimetric moisture content in four different softwoods commonly present in the Spanish and European markets, based on electrical resistance measurements. This improved moisture content estimation is useful not only for assessing the quality of wood products, especially in the case of laminated products, during the transformation and delivery process, but also for accurately monitoring the evolution of moisture in wood present in bridges and buildings, which is of great importance for its maintenance and service life improvement.Area of study: The study was carried out on samples of Scots, laricio, radiata and  maritime pines of Spanish provenances.Material and methods: On 50x50x20 mm3 solid wood samples (36 per species, 9 per condition), conditioned at 20ºC (±05ºC) and 40±5%, 65±5%, 80±5% or 90±5% Relative Humidity (RH), electrical resistance and oven-dry moisture content was measured. The Samuelsson's model was fitted to data to explain the relationship between the two variables. The accuracy of the model was evaluated by the use of an external sample.Main results: With the proposed mathematical functions the wood moisture content can be estimated with an error of ±0.9% in the four species, confirming the effectiveness of this nondestructive methodology for accurate estimation and monitoring of moisture content.Research highlights: our results allow the improvement of the moisture content estimation technique by resistance-type methodologies.Keywords: Resistance-type moisture meter; species correction.Abbreviations used: MC: Moisture content; RH: relative Humidity; R: electrical resistance; RP: wood electrical resistance measured parallel to the grain; RT: electrical resistance measured perpendicular (transversally) to the grain; GM-MC: gravimetrically measured moisture content

Aplicación de los ultrasonidos a la evaluación de las propiedades mecánicas de la madera en rollo de pequeño diámetro

In this study is shown the mechanic characterization results carried out with small round timber (diameter under 23 cm) of laricio pine (Pinus nigra subsp. Saltzmannii) from Cuenca forest. According to EN 14251:2003 445 small round timber of 8, 10, 12 y 14 cm are tested, concluding they can be assigned to C14 strength class (according to UNE-EN 338:2003). The suitability of ultrasound transmission method to grade this material is evaluated, proposing several strength grades combination (C22/C16/R, C18/C14/R ó C18/R) which are based on values of the indicating property of the ultrasound wave velocity. For each strength classes combination obtained, the grade yield is analyzed and compared with optimal ranking results developed according to UNE-EN 14081-2:2005. Finally, method feasibility related to predict the presence of growth specific singularities (juvenile wood specially) is concluded, in addition to the convenience to establish mix grading methods based on ultrasound and visual evaluation together.En el presente trabajo se presentan los resultados de la caracterización mecánica efectuada sobre madera en rollo delgada (diámetro inferior a 23 cm) de pino laricio (Pinus nigra subsp. Saltzmannii) procedente de los Montes de Cuenca. Se ensayan, de acuerdo con la norma EN 14251:2003, un total de 445 rollizos torneados con diámetros finales de 8, 10, 12 y 14 cm, concluyéndose que el material sin clasificar puede ser asignado a una clase de resistencia de C14 (según UNE-EN 338:2003). Se evalúa la aplicabilidad del método de transmisión de ondas ultrasónicas en la clasificación del material proponiendo diversas combinaciones de clases de resistencia (C22/C16/R, C18/C14/R ó C18/R) en función del valor de paso empleado para la velocidad de la onda ultrasónica. Para cada combinación de clases resistentes obtenida se analiza el rendimiento clasificatorio, el cual es comparado con los resultados de una clasificación óptima del material (Optimal Ranking) efectuada según los principios establecidos en la norma EN 14081-2:2005. Finalmente se concluye sobre la aplicabilidad del método en la predicción de la presencia de determinadas particularidades del crecimiento (en especial madera juvenil) así como sobre la conveniencia de establecer métodos mixtos de clasificación basados en el empleo conjunto de evaluaciones visuales y por ultrasonidos

Improving the accuracy of wood moisture content estimation in four European softwoods from Spain

Centro de Investigación Forestal (CIFOR)Aim of study: To obtain improved models to predict, with an error of less than ± 2.0%, the gravimetric moisture content in four different softwoods commonly present in the Spanish and European markets, based on electrical resistance measurements. This improved moisture content estimation is useful not only for assessing the quality of wood products, especially in the case of laminated products, during the transformation and delivery process, but also for accurately monitoring the evolution of moisture in wood present in bridges and buildings, which is of great importance for its maintenance and service life improvement. Area of study: The study was carried out on samples of Scots, laricio, radiata and maritime pines of Spanish provenances. Material and methods: On 50x50x20 mm3 solid wood samples (36 per species, 9 per condition), conditioned at 20ºC (±05ºC) and 40±5%, 65±5%, 80±5% or 90±5% Relative Humidity (RH), electrical resistance and oven-dry moisture content was measured. The Samuelsson's model was fitted to data to explain the relationship between the two variables. The accuracy of the model was evaluated by the use of an external sample. Main results: With the proposed mathematical functions the wood moisture content can be estimated with an error of ±0.9% in the four species, confirming the effectiveness of this nondestructive methodology for accurate estimation and monitoring of moisture content. Research highlights: Our results allow the improvement of the moisture content estimation technique by resistance-type methodologies.Laboratories of Wood Technology of-CIFOR-INIA and University of Cordoba BIA2013-42434-RPeer reviewed8 Pág

Height growth for assessing core–outerwood transition on Pinus sylvestris and Pinus nigra Spanish stands

6 Pág.One of the characteristics of great relevance in the wood quality in Spanish coniferous forests due to growth conditions is the presence of corewood. This wood area presents properties and characteristics inferior to those in outerwood, which are more appropriate for certain uses. In plantations with short rotations, the percentage of juvenile timber is higher, and the profitability of the wood can be affected due to its unsuitability for high added value applications, such as structural. This work focuses on determining whether the use of models of current annual increase in height can provide suitable estimations of the year or transition zone between corewood and outerwood. This knowledge will contribute to analyze the expected yield of quality wood. The material studied is from Pinus sylvestris L. (Scots pine) and Pinus nigra Arnold subsp. nigra (black pine) pure stands. Densitometry results showed that the corewood–outerwood transition year could not be predicted by tree height functions.This study has been carried out with the support of the Ministry of Economy and Competitivity of the Government of Spain through the Project RTA2014-00005-00-00, and the Training Program for Research Staff (FPI-INIA).Peer reviewe