Basic density and selected strength and stiffness properties of kiln-dried Pinus caribaea wood

Abstract

Pine species are widely commercialized for its wood and has intentionally been introduced to establish forest plantations since the second part of the 19th century. Wood has to be dried to improve workability, acoustic properties, resistance to biodegradation, compatibility and strength properties. However, wood is a visco-elastic material dependent on time domain, temperature and moisture content yet this response is poorly understood and documented. Kiln-drying has influences on the stiffness and strength properties of wood hence the drying process affects wood performance. Basic density is a good predictor of stiffness and strength properties. Therefore this study seeks to contribute to better utilization of Kiln-dried Pinus caribaea wood in timber construction to ensure safety and durability by determining basic density, modulus of elasticity and compression parallel to the grain. Test specimens were prepared and tested for Basic density (50 samples), Modulus of elasticity (MOE) and compression parallel to the grain using a Testometric AX M500 – 50KN Universal Testing Machine in accordance with British Standards BS 373. For comparison purposes, samples for MOE and compression parallel to the grain were kiln-dried to different moisture content classes below fiber saturation point (12%, 19% and 26%) with 30 samples for each class. The data was statistically analyzed using one-way Analysis of Variance test and independent sample t-test. The results indicated that P. caribaea had a mean basic density of 486.7 Kgm-3 , mean MOE and compression parallel to the grain were highest at 12% moisture content and lowest at 26% moisture content. There was a significant difference in MOE and compression parallel to the grain of kiln-dried P. caribaea wood at 12%, 19% and 26% moisture content levels. The compression parallel to the grain and MOE of kiln dried P. caribaea wood at 26% was not significantly different from that of air dried P. caribaea wood. It was recommended that timber users in Uganda should be sensitized about varying strength and stiffness properties with moisture content of the P. caribaea wood on market so that their serviceability and prices reflect their inherent properties. Further studies aimed at determining the variation of stiffness and strength properties of wood of different species at different moisture contents would align end use with timber quality.