Rolling shear modulus and strength of cross-laminated timber treated with micronized copper azole type C (MCA-C)

Abstract

The effect of micronized copper azole type C (MCA-C) treatment on rolling shear (RS) strength and RS modulus of cross-laminated timber (CLT) was evaluated. The CLT test specimens were either constructed with untreated 2 × 6 (38 mm × 140 mm) No. 2. southern yellow pine (the United States grown) laminations or MCA-C treated laminations. The shear-free modulus of elasticity (Esf) and longitudinal-radial shear modulus (GLR) of the laminations were non-destructively measured prior to CLT manufacturing. The average Esf and GLR of the untreated lumber were 11.08GPa and 231.42 MPa, respectively, while those of the treated lumber were 9.60GPa and 236.01 MPa, respectively. Four-point bending test described in EN 16,351 standard along with the Shear analogy method was adopted to measure the RS properties. The preservative treatment decreased the mean RS strength, while it increased the mean RS modulus. However, the differences in the means were not significant based on one-way analysis of variance and Kruskal-Wallis H test, respectively. The experimentally obtained bending stiffness of the CLT test specimens and the RS strength estimated using the simplified method described in the CLT Handbook were compared against the values obtained based on the Shear analogy. The agreement between these two approaches indicates that the short-span test setup implemented in this study and the simplified method can be used for measuring bending stiffness and estimating RS strength of 3-ply CLT.