Use of low grade hardwoods for fabricating laminated railway ties

Abstract

Solid wood railway ties have widely been used in the railway system in North America. With decreasing average log diameter and quality, laminated wood railway ties have been developed but used on a very limited scale due to the added cost for adhesive and labour. With significant technological advances made by the wood adhesive industry recently, it is considered timely to investigate the feasibility of fabricating laminated wood railway ties using the new structural adhesives. This study was aimed at developing laminated railway ties using low grade hardwoods to meet the North American performance specifications. A two-component polyurethane structural adhesive was used to bond hard maple (mainly) and yellow birch (limited) lumber of No. 3B Common grade to manufacture 16 ties following four fabricating procedures. The modulus of elasticity (MOE) and modulus of rupture (MOR) of laminated wood ties were evaluated. The key findings were (1) the average MOR of the ties of type A-2 (i.e., laminating first followed by creosote treatment) met the AREMA specifications, however, the average MOE was 3% lower than the required value; and (2) both MOE and MOR of the ties of type A-3 (i.e., CCA treatment first followed by laminating) satisfied the specifications. It is feasible to fabricate laminated wood ties using low grade (No. 3B Common) hardwoods and a proper structural adhesive.