Unsawn timber of 22x90x2000 mm (thickness, width, and length, respectively) and wooden lamellas with Finger Joint of 22x60x650 m (thickness, width, and length, respectively) from Pinus tecunumanii wood were used. The Company Cipreses de Colombia SA provided the wood, from mature trees (25 years old) collected from plantations located in the municipality of Yolombó (Antioquia, Colombia).

It was used Polyvinyl alcohol (PVA) adhesive, a water-soluble synthetic polymer used in a variety of applications, with a density around 1.19 g cm^-3, pH in the range of 6.0 to 7.0, making it generally neutral or slightly acidic; resin content usually from 40 to 60% weight. The rate of application was 200 g m^-2 on one side of the piece of wood. Pressing was carried out at 8.0 MPa for 60 min. In total, 12 three-layer CLT panels were manufactured; six boards with a Finger Joint system (Figure 1) and six with solid wood plank system (Figure 2). Each board sizes up to 240 mm wide x 1,800 mm length and a final thickness of 60 mm (EN 16351). The wood board samples were not organized or oriented in a specific radial, or tangential way. Instead, the tables were joined at random, as can be seen in Figures 1 and 2, where the arrangement is observed without a definite pattern. In addition, in Colombia there is no established standards for the visual structural classification of wood, which prevented such activity.

Figure 1

Figure 2

The properties evaluated in each of the panels were density, modulus of elasticity and modulus of rupture following the method of the UNE-EN 408 standard (UNE 2011). It was performed with a random positional sampling on each CLT panel. Tests were performed using a load frame with a 40,000 kg capacity and a data processor Unitronics (Figure 3).

Figure 3

The statistical analysis was performed using a completely randomized design for each test. The information was processed based on the methodology described by Hoshmand (2006).

The results of the air-dry densities obtained for (CLT) panels made with Pinus tecunumanii wood with the Finger Joint and solid wood planks systems are presented in Table 1.

Table 1

The results of air-dry densities obtained for CLT panels made from Pinus tecunumanii wood using two different manufacturing systems, the solid wood planks, and the Finger Joint systems are presented. These results are crucial to assessing the suitability of this species for the manufacture of CLT panels, a material that is increasingly used in construction due to its mechanical and physical properties. As shown in Table 1, the dry density values obtained for CLT panels manufactured with both systems were 626.05 kg m^-3 for panels produced with the solid wood planks system and 679.03 kg m^-3 for those manufactured with the Finger Joint system. Both values are in the middle density range, which according to ASTM classification is between 510 and 750 kg m^-3, suggesting that Pinus tecunumanii CLT panels may be a viable alternative for structural applications. The average densities obtained for the panels with the solid wood planks system and with the Finger Joint system revealed that there was not significant difference (Table 2), indicating that both manufacturing methods result in materials with similar density characteristics. This is relevant as it suggests that regardless of the manufacturing system used, a material with density characteristics that meets ASTM requirements for the manufacture of medium-density CLTs can be obtained.

Table 2

It is important to note that density is a key parameter in determining the mechanical and physical properties of CLT. The density of a material is directly related to its strength and stiffness, which affects how well cross-laminated timber (CLT) can support structural loads. In this study, the density values obtained for Pinus tecunumanii were higher than those reported in other studies conducted with different species of pine, such as Pinus taeda, Pinus elliottii, Pinus radiata, Pinus echinata, Pinus ponderosa, and Pinus sylvestris with density values ranged from 360 to 500 kg m^-3 for CLT (Godoy et al. 2017; Baño et al. 2018; Glasner et al. 2023; Brandner et al. 2024). This difference could reflect the inherent properties of Pinus tecunumanii wood, which has a higher density and therefore could provide a higher quality material for construction.

The results of the mechanical characterization for the static bending of CLT panels made of Pinus tecunumanii wood, using the Finger Joint and solid wood planks systems, are presented in Table 3. This characterization is essential to evaluate the behavior of CLT panels under bending loads and determine their suitability for structural applications. Both the modulus of rupture (MOR) and the modulus of elasticity (MOE) of panels manufactured with both systems were evaluated. The values obtained for MOR and MOE are indicative of the strength and stiffness of the panels, two key factors for their use in the construction of structural elements.

Table 3

For panels manufactured with the solid wood planks system, the MOR was significantly higher than that of panels produced with the Finger Joint system, reflecting a greater resistance to static bending in the first system evaluated. This is due to the continuity of wood fiber in solid planks, which contributes to greater structural strength. On the other hand, panels manufactured with the Finger Joint system showed a lower MOE value, which implies a lower stiffness under load.

In particular, panels manufactured with the Finger Joint system showed a MOR of 29.82 MPa, which is below the minimum limit recommended by ASTM (39 MPa). This value reflects a very low resistance compared to the requirements for more rigorous structural applications. For the boards manufactured with the Solid wood planks system they showed a higher MOR of 41.59 MPa. In addition, both manufacturing systems presented different values of MOR, with statistically significant differences between them (Table 4), which suggests that the Solid wood planks system offers a higher strength compared to the Finger Joint system. Comparing these results with those reported for other species of the same genus, such as Pinus radiata, Pinus taeda, Pinus echinata and Pinus silvesrtis, the values obtained for Pinus tecunumanii were higher than those obtained for CLT manufactured with these species, with a reported MOR between 20-30 MPa (Godoy et al. 2017; Baño et al. 2018; Li et al. 2021; Glasner et al. 2023; Olsson et al. 2025).

Table 4

The results obtained for the MOE in static bending of CLT panels manufactured with Pinus tecunumanii show significant differences between the two manufacturing systems evaluated (Table 5); for the Finger Joint system, the MOE was 9081.86 MPa, with a confidence interval between 6,962 and 9,807 MPa; this value is classified as low according to the standards established by ASTM, which consider a minimum MOE of 10,000 MPa for structural woods in more demanding applications. On the other hand, panels manufactured with the solid wood planks system presented an MOE of 13,454.9 MPa, with a confidence interval between 9,904 and 14,710 MPa; this value is classified as medium strength according to ASTM standards. These statistical differences between the two manufacturing systems were significant, indicating that the solid wood plank system offers greater rigidity compared to the Finger Joint system. This difference could be related to the fiber continuity in panels made of solid wood planks, which provide greater resistance to bending and better load distribution. Compared to CLT boards made from other species, such as Pinus ellioti, Pinus radiata and Pinus taeda, the values obtained for Pinus tecunumanii were higher. According to previous studies by Godoy et al. (2017), Baño et al. (2018) and Li et al. (2021), the CLT panels of these species had MOE values in the range of 6,000-8,000 MPa, which are lower than the results obtained in this study for Pinus tecunumanii. On the other hand, for Pinus sylvestris wood, results were similar, according to Olsson et al. (2025).

Table 5