Three-dimensional tests on hygric properties of laminated bamboo and bamboo scrimber

Laminated bamboo (LB) and bamboo scrimber (BS) are two emerging industrial bamboo products that are considered to have potential as environmentally friendly building materials. As hygroscopic plant fiber-based materials, their hygric properties have important impacts on construction durability, indoor hygiene and building energy consumption. The study aims to clarify the hygric properties of LB and BS through testing and analysis. Four test items are carried out, including sorption test and water immersion test for the moisture storage-related properties, and capillary absorption test and water vapor transmission test for the moisture transport-related properties. Considering the anisotropy of bamboo, the tests for transport-related properties are carried out in longitudinal, radial and tangential directions. Based on the test results, the comparison of LB and BS in different directions shows that the moisture transport rate in longitudinal direction is far higher than the rest two directions, and in general, the transport rate in radial direction is lower than that in tangential direction. The comparison of LB and BS with corresponding reference timber shows that LB and BS have both lower moisture storage and moisture transport capacities than reference timber. In addition, a relative humidity-related mould growth is observed, showing that the critical relative humidity for mould growth on LB and BS is lower than the internationally used value (80%) for timber. This results in bamboo facing a greater risk of moisture damage than timber in practical applications. The study provides a first-hand tested parameter set and clarifies the characteristics of hygric property for LB and BS in three dimensions, which forms a knowledge basis for their proper application under different working conditions.