Biological durability of preservative treated cross-laminated timber (CLT) made with southern pine lumber

Bradia Henfield; Tamara Suely Filgueira Amorim França; Frederico Franca; Franklin Quin Jr; Katie Ohno; Rachel Arango

Authors

Bradia Henfield Arxada
Tamara Suely Filgueira Amorim França Mississippi State University
Frederico Franca Mississippi State University
Franklin Quin Jr Mississippi State University
Katie Ohno USDA Forest Products Laboratory
Rachel Arango USDA Forest Products Laboratory

Abstract

Cross-laminated timber (CLT) is an engineered wood product that is being increasingly utilized in structural applications. However, its susceptibility to fungal decay and termite attack raises concerns about long-term durability, particularly in high-moisture and insect-prone environments. This study evaluates the biological durability of CLT fabricated with southern pine and treated post-layup with two copper-based preservatives: copper azole (CA-C) and micronized copper azole (MCA) under laboratory conditions. Fungal decay resistance was assessed using brown-rot (Serpula lacrymans) and white-rot (Irpex lacteus) fungi, while termite resistance was evaluated through exposure to Reticulitermes spp. Results showed that preservative treatments significantly reduced fungal decay and termite damage compared to untreated controls, although treatment effectiveness varied with CLT configuration (3-ply or 5-ply). While both preservatives effectively mitigated decay in 3-ply panels, treated 5-ply panels exhibited comparable mass loss to untreated counterparts. Termite resistance tests demonstrated that MCA and CA-C treated CLT samples exhibited significantly lower mass loss and higher termite mortality compared to the untreated controls, with both preservatives providing comparable protection.

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