Solid wood railway ties have been in service on the railway system in North America. The commonly used species in eastern Canada are hard maple, soft maple and yellow birch. With decreasing average log diameter, laminated wood railway ties have been developed and used for many years on a very limited scale. It is believed that the added cost for adhesive and labour are the main reasons that laminated ties have not been more widely used. With significant technological advances made by the wood adhesive industry in the last two decades, the
selection of suitable adhesives which may also impact on the labour cost is worth revisiting. The objective of this project was to manufacture laminated railway ties using low grade hardwoods, which meet the North American performance specifications. Three structural adhesives (two polyurethane types and one phenol-resorcinol formaldehyde type) were selected and their performances were evaluated via shear block tests. Low grade hard maple (mainly) and yellow birch (limited) lumber was used to manufacture 16 ties using four fabricating approaches, and their critical mechanical properties, such as modulus of elasticity (MOE) and modulus of rupture (MOR), were evaluated.
The key findings are 1) The suitable structural adhesive was polyurethane-based, i.e. WD3-A322 / CX-47 in terms of shear block tests; 2) In comparison to glued laminated lumber ties, the MOR values of those ties made using the A-2 procedure (laminating first followed by creosote treatment) met the performance specifications outlined by AREMA, however, the average MOE value was 3% lower than the required value; and 3) Both MOE and MOR values of those ties made using the A-3 procedure (CCA treatment of boards, followed by laminating) satisfied the performance specifications outlined by AREMA for glued laminated lumber ties. In summary, it can be concluded that it is feasible to fabricate laminated wood ties using low grade (3B) hardwoods and a proper structural adhesive, which can produce satisfactory performance in terms of MOE and MOR. The laminating and creosote-treating procedure used in this study showed promising results in terms of practicality, economics and performance. It is recommended for future research to investigate additional performance requirements of ties in both laboratory and field service testing. Testing to meet such additional requirements includes flexural fatigue, rail/plate area compression, spike/screw pullout, fastener uplift, and weathering resistance. It is also recommended to work with industrial partners to further develop a cost-efficient fabricating approach at the pilot and industrial scale. Keywords: Chemical treatment, laminated product, modulus of elasticity, modulus of rupture, railway ties, shear strength, structural adhesive.