Assessment of physical, mechanical, and chemical properties of Dendrocalamus asper bamboo after application of wetting and drying cycles

Given the hygroscopic nature of bamboo and its reduction in strength with increasing moisture content, we evaluated the effects of hornification - generated through the application of drying and rewetting cycles - on the physical, mechanical, and chemical properties of the culms of Dendrocalamus asper. Our objective was to assess if the treatment would cause a reduction in water uptake, an increase in the dimensional stability of bamboo, and a stiffening of the material, increasing its mechanical strength. Specimens were submitted to a maximum of 15 cycles, being immersed at room temperature (22 +/- 3 C) and dried at 50 +/- 5 C. Absorption capacity, dimensional stability, density as measured with a helium pycnometer, tensile tests, scanning electron microscopy (SEM) analysis, X-ray diffractometer (XRD) and Fourier-transform infrared spectroscopy (FT-IR) were undertaken. Hornification increased the dimensional stability of bamboo proportionally to the number of cycles applied, and a 5.8 % increase in cross section was seen after 264 h for 15 cycles. The control samples increased by 17.8 %. Reduction in the water absorption was not verified for treated bamboo. The elastic modulus was maintained and the tensile strength after treatment was reduced (258.6 MPa for control and 207.5 MPa after 15 cycles). Chemical analysis and microscopy did not show any significant changes in the composition of the bamboo after the application of wetting and drying cycles.