Effect of disodium octaborate tetrahydrate on the mechanical properties of Dendrocalamus asper bamboo treated by vacuum/pressure method

Abstract

The chemical treatments applied to some lignocellulosic resources commonly used as building materials can influence their mechanical performance during service, and hence, this effect should be studied for structural safety reasons. In this piece of work, prismatic samples of Dendrocalamus asper bamboo were treated in a vacuum/pressure process with disodium octaborate tetrahydrate (DOT) solutions and the corresponding mechanical performance was compared with non-treated and water-treated samples. Full penetration of boron was achieved, with DOT retentions of 14.79 kg m −3 and 21.79 kg m −3 for 5% and 8% (wt/wt%) solutions, respectively. Dynamic modulus of elasticity (MOE), static MOE, and compressive modulus of elasticity of the material, with values between 23.3-24.0, 15.9-16.2, and 26.2-27.2 GPa, respectively, were statistically equivalent for all the analyzed treatment conditions. However, a significant influence of the treatment could be observed on the specific compressive strength of bamboo, showing an increase of 35.3% for the 5% solution and 30.6% for the 8% solution. Although without statistical difference among the treatments, similar behavior was observed on the specific modulus of rupture (MOR) under flexural loading, with an increase of up to 10.1% in relation to the reference for the treated samples. The results achieved in the present study from nondestructive excitation pulse, three-point bending, and axial compression tests demonstrated that mechanical behavior of bamboo was preserved or even enhanced by the proposed treatments based on disodium octaborate tetrahydrate.

Preservative treatment and chemical modification of bamboo for structural purposes

“…The T10HB5 treatment presented the highest values for MOR and MOE, with an increase of 13.38% and 8.9% respectively, in comparison with untreated samples. The observed increase on the fc, MOR and MOE of the samples treated with boron corroborates with the results reported by Gauss, Kadivar and Savastano Jr. (2019) confirming that DOT improves the overall mechanical properties of bamboo.…”

“…Boron compounds are some of the most effective and versatile preservative solutions used today since they combine broad-spectrum efficacy, low mammalian toxicity, and are odourless and colourless (TONDI et al, 2012a;DONMEZ CAVDAR;MENGELOĞLU;KARAKUS, 2015;JIT KAUR, 2018;ZHOU et al, 2018). Preservation with boron compounds can even improve the quality of bamboo, improving some mechanical properties in comparison with bamboo without preservatives in samples with high retention levels (PRININDYA; ARDIANSYAH, 2014;SULAEMAN et al, 2017;SAVASTANO JR, 2019). Nevertheless, the use of boron compounds presents restrictions for the treated material because of the leaching of boron in the presence of water, making it unsuitable for use in exterior applications (HIDALDO-LÓPES, 2003;FREEMAN;MCINTYRE;JACKSON, 2009;CALDEIRA, 2010).…”

“…Various bamboo treatment techniques such as chemical, heat, and oleo-thermal treatments have been demonstrated, in both academic and industrial levels. Treatment using chemicals, as an effective way to improve durability and stability, is the most frequently investigated treatment for wood and bamboo materials (HILL, 2006;ZHANG et al, 2014;ESSOUA et al, 2016;SCHORR;ESSOUA ESSOUA, 2018;SAVASTANO JR, 2019). Chemical preservatives can permanently alter material cell wall polymers and deposit chemicals in cell voids (HILL, 2006;FENG et al, 2014).…”

“…2 -Absorption of the solution after the treatment process in the vacuum/pressure vessel. Source: (GAUSS; KADIVAR;SAVASTANO JR, 2019) …”

Tensile Strength of Bamboo After Preservation

“…Efforts to overcome the low durability of bamboo, it is essential to preserve bamboo before using it. There are many methods of preserving bamboo, either by simple means without chemicals or by adding chemicals (Chen et al n.d.;Daud et al 2018;Gauss et al 2019;Industri and 2017 n.d.). Bamboo preservation in a simple way can be done by soaking bamboo in water for a certain duration or boiling it.…”