Subject matter

Bamboo, both in its full-culm (pole) form and as a constituent material in a variety of engineered bamboo materials (glue-laminated bamboo, cross-laminated bamboo, bamboo scrimber, etc.) is receiving considerable interest as a material for construction. Bamboo has remarkable potential to reduce the environmental impact of the construction sector and has the demonstrated potential for promoting social and economic equity, particularly in the Global South.

There are about 1600 bamboo species globally. On the order of 100 species are believed to be suitable for construction applications although only a handful are currently economically viable in this sector.

Bamboo is a rapidly maturing plant that is harvested on a 3-to-6-year cycle. Bamboo culms are approximately tapered cylindrical tubes having transverse diaphragms (nodes) located along their length. Bamboo, like wood, is a lignocellulosic material achieving its strength from its cellulose fibres. Unlike wood, bamboo is highly anisotropic (more so than even pultruded FRP materials) requiring robust means of assessing material properties and behaviour, especially those related to splitting - of which bamboo is prone. 

Bamboo construction, especially full culm construction, is most common in South East Asia and Latin America although remains largely a marginal material: viewed as being of lower quality and suited only to temporary applications. This could not be further from the truth. In the Global North, engineered bamboo is gaining considerable traction in the construction industry primarily based on its perceived sustainability credentials. Nonetheless, surprisingly little material characterisation is employed on the bamboo used in engineered products.

Although important advances have been made to standardise the use of bamboo, many technical challenges remain before bamboo can be fully accepted as a structural material. It is still necessary to provide builders, engineers, and architects with tools to allow them to select bamboo in construction design. Improved knowledge for working with bamboo will support innovation in the engineered bamboo industry: one cannot produce an engineered material, without understanding the constituent materials.

Uniformly accepted and robust methods of characterising bamboo materials are necessary. While there are extant materials test methods (e.g., ISO 22157:2019), these provide no guidance as to what properties are required for design and, critically, how these properties may interact. A widely acknowledged shortcoming of existing bamboo standards is that there is no single property (or small handful of properties) that can reliably characterise bamboo materials (as compression testing does for concrete). A second acknowledged barrier to bamboo construction is the largely ad hoc and variable nature of available material property data. Harmonisation and synthesis of both test methods and data curation are required. A global  Technical Committee (TC) is critical to addressing this need.

In particular, the proposed TC proposes to analyse the state-of-the-art and the state-of-practice associated with bamboo materials characterisation. The focus will be on constituent bamboo material either "raw" or processed for full-culm construction or engineered bamboo products and composites for structural components and buildings.

The TC will start from already well-established tension, compression, shear and bending tests, with the aim of harmonising these. The TC will then broaden its scope to address critical needs in bamboo materials characterisation: splitting behaviour, dimensional stability, durability and ageing, creep behaviour and more detailed needs such as hardness, dynamic, and fracture mechanics characterisations. The direction of the TC will be guided by the needs of the bamboo design community which will be represented on the committee.

An over-riding objective is to establish a simple and easy-to-use classification methodology (or procedure) that will be largely independent of bamboo species, similar to timber classifications of softwood and hardwood.

Terms of reference

• The TC will convene for five years, with several milestones in that horizon.
• This TC is expected to gather approximately 25 members from academia, industry, consulting and policy sectors. Great attention will be made to achieving diverse representation from a wide geographical range of countries, particularly those representing the Global South where the impact of this TC's activities will be felt most strongly. PhD students and young researchers will be involved in order to start to develop continuity of leadership in the field.
• The TC work will draw on the experience of its members (and ultimately their networks) with mechanical testing of bamboo from different geographical areas with bamboo of different geometries with the goal of establishing species- and region-independent characterisations of bamboo.
• The work will be carried out as a RILEM committee in an independent and neutral environment.
• The TC's scope will be the basis for further standardisation and complement the already published ISO 22157 document. It will form the framework for writing guides, commentary, state-of-the-art reports, etc. (all activities that are not practical in the standards-development ISO environment). The RILEM TC will provide also an excellent opportunity for synthesis and harmonization. Of particular importance is synthesising bamboo materials characterisation with engineered bamboo production – a field that is presently neglected.

Detailed working programme

Task 1 Review, Gap Analysis and Prioritisation (priority in year 1 and ongoing beyond that)

• Literature review of existing test methods regardless of standardisation; Synthesis of large datasets that may be available in the literature.
• Identifying gaps in current practice. These may include the compression, tension, shear, and bending tests in the direction parallel to the fibre and orthogonal to these, extended to torsion, ageing and durability, resilience and hardness testing. Prioritisation of needs.
• Define [more advanced] tests not already established dynamic tests, creep and relaxation tests, and others; always informed by the needs of the bamboo industry.

Deliverable:  state-of-the-art report (and annotated bibliography) on existing test methods (including variations thereof).

Task 2 International Database (initiate with Task 1 and ongoing throughout the life of the committee)

• Based on Task 1, establish an appropriate protocol for data collection and dissemination, placing existing (Task 1.1) data and new data into this format (A key aspect of having practical deliverables is the selection of bamboo species for focus on Tasks 3 and beyond).

Deliverable: Open Source publication of initial database (online repository; Zenodo?) – this task will include ongoing curation of data as it is developed. One committee member will be responsible for such curation.

Task 3 Oversight of Round-Robin Testing

• Identify resources to support the need for test programs. This will need to be done in Year 1, so that resources will be available going forward.
• Establish round-robin type test programs for tests identified in Task 1.2 with objective of harmonising and improving standard test methods.
• Establish pilot test programs for tests identified in Task 1.3
• Continuous curation of Task 2

Deliverables: Results of test programs will be reported by appropriate authors. Coordination of efforts and peer review will be provided by TC.

Task 4 Classification and Grading Synthesis (Year 4+)

• Based on successful Task 3, an expanded database (Task 2) will be exploited with the objectives of identifying:

1. potential classification approaches for bamboo
2. potential universal grading criteria

        Deliverables: TC Synthesis Report

Task 5 Quantification of Sustainability Credentials (this task will be conducted by a subcommittee within TC)

• Task 4 will parallel Tasks 1 through 5 with the objective of accurately capturing the sustainability credentials of bamboo (carbon capture, embodied carbon, etc.)

Deliverables: TC Synthesis Report

Task 6 Recommendations for Standard Test Methods (Year 5)

• Considering ISO standards and others identified in Task 1, recommendations for harmonised test methods and bamboo characterisation will be developed from the wisdom of the TC. The TC is well-placed to seeing these implemented.