236-BBM : Bio-aggregates based building materials
Technical Committee 236-BBM
Deputy Chair: Florence COLLET
Activity ending in: 2016
The work of the Technical Committee (TC) will be to study construction materials made from plant particles. Are concerned building materials containing as main raw material renewable, recyclable and easily available plant particles. These materials are obtained from the processing of hemp, flax, miscanthus, pine, maize, sunflower, bamboo ... The TC will focus on particles and as well on fibres issued from the plant. However, composite materials designed from fibres and polymer matrix will not be considered within the framework of this TC. They deserve constitution of a full-fledged technical commission. These particles and fibers are used as aggregates or admixtures in combination with one binder or more. All binders which are compatible for use with plant material will be considered in the TC’s work. The binders can be from mineral (cement, lime...), plant as well as from animal origins.
The first objective of the TC will be to identify all of these materials because many studies have been done and are still initiated. Main issue is to meet the expectations of building materials with low environmental impact. TC will focus on two main objectives. Each of them could be achieved in eventually separated workshops. First objective concern organic raw material characterization for aggregate use. Second one aim to qualify multiphysics properties of these specific concretes.
The first objective will be to characterize this particular plant material. It differs from conventional aggregates of mineral origin both by their shape, microstructure and mechanical and chemical characteristics. The plant material is in the form of fibres or grains whose shape departs from a sphere. It is therefore necessary to define new methods to characterize the shape and porosity of these materials. This porosity is the foundation of many of the final composite properties, from mechanical or thermal to acoustic ones. This work is important in the goal to make reliable use of these new aggregates. Indeed, numerous variety, cultivation methods, weather conditions as well as transformation tools can widely influence organic aggregates physical properties and consequently organic concretes ones.
The second objective relates to the composite materials compounded from vegetable particles and one or several binders performances. It is now well established that when mixing raw materials in the presence of water, matters dissolution may occur and modify significantly the setting and hardening of the binder. The work will aim to clarify these physico-chemical interactions to write mixtures formulations guides. Various studies have shown that these concretes enable to elaborate a wide range of mixes in varying the binder / plant particle ratio. It is therefore important to measure various properties of these concretes in order to adapt the formulations according to target applications in structures, thermal or acoustic insulation...
In summary, the working group will provides a comprehensive view and a critical review of :
- characterization of the raw materials to make mixtures for various applications
- measurement of multi-physical material performances (mechanical, thermal, acoustic).
Links between these two objectives are really narrow and it is difficult to split this TC in two different parts as composites properties are greatly dependant on organic aggregate ones. Analysis must be driven in a TC teaming up physicians, mechanical scientists and bio-chemists skills. Subgroups could be eventually constituted around more specific topics.
The TC will limit its investigation scope to the non-usual properties of raw materials and those of elaborated materials.
However, the various building systems designed with these materials are not considered within this Technical Committee scope. Their studies may be investigated by another technical committee.
Same comment can be expressed concerning life cycle analysis of these concretes. A mess of hypothesis are still missing strong scientific basis especially regarding life duration, recycling ... It seems to be necessary to dedicate a specific TC to these topics.
Terms of reference
The expected work duration is 5 years.
During the first year, a first international symposium will be organized to identify precisely the different materials typology.
This will enable to make up on works concerning the different kind of materials. A summary will be given as state of the art.
This initial assessment will then permit to focus the work on group's specific goals.
The first objective relates to plant sourced raw materials characterisation. A review of various methods will be done and then crossover studies will be conducted between the different teams. First direction will be to compare the performances of these techniques and second one to clarify its applicability.
Several important features will require developments but it seems that morphology measurement and microstructures characterisation are a priority.
This step will lead during the 3rd year to write characterisation test methods for these materials from plant origin used in building field. It may also lead to the writing of a LCA procedure for these materials.
Secondly, regarding concrete performances, work will focus on concrete features allowable limits establishment and validation. This has to be done in purpose of the required uses listed. More conventional measurement method will be as well refined and tested.
A final international conference will be organized to share obtained results for these two purposes and perhaps to start a new group geared towards the development of efficient building systems incorporating these bio-materials.
The group will consist of academic members working for several years on these subjects. Following academic institutions have been identified to contribute to the TC. These institutions are not only specialized in civil engineering and construction but also in bio-chemistry and biophysics of plant material.
The group will also be open to participation for both institutional representatives of each field (linen, hemp sector...) but also to the industrials of these fields (manufacturers of binder, prefabricated blocks ...).
Detailed working programme
The main goals are the following ones.
After the first meeting the project of the TC will be based on the following actions:
A1 - Characterization of the organic aggregate
- Identification and categorization of the principal parameters.
- Adaptation and suggestion of test measurement protocol for each parameter.
- Drafting of the aggregate characterization test procedure.
A2 - Mix proportioning of bio-aggregate based building material
- Development of reference material according to the objective.
- Drafting of material mixing and casting test procedure for mixing and casting of the material.
A3 - Multi physical performances of bio-aggregate based building material
- Write the state of the art in all functional areas of organic aggregate based composites.
- Write performances summary for these materials.
- Methods (reliability, performance ...) comparison and critical analysis based on a Round Robin Test.
Plant material used as raw material for building construction is relatively recent and original topic. It is naturally linked with the TC from concrete formulation and performance measuring domains. However, vegetables matters attendance as main components makes this work original. There is no similar group within the ACI.
Work of the TC lead to the drafting of several documents:
- Initial state of the art on the use of plant material in building field,
- Recommendation on the characterization of the raw vegetable matter in its various forms,
- User guide or even procedure formulation procedure for construction materials made from plant matter,
- Testing procedures for characterising these building materials performances,
- Synthesis documents to the attention of researchers, professionals, craftsmen, owners, contractors…
Group of users
Many persons involved in construction field may be concerned by these works outcomes. First, state of the art will help to better target research programs to carry out in order to remove vegetable based materials development bolts. Researchers will then find a way to better coordinate their actions in progress and future.
Moreover, testing and characterization procedures establishment will allow a wide and secure diffusion of these materials on the market. Finally, information diffusion actions will contribute to the networks development among professionals as architects, craftsmen, owners, contractors…
Specific use of the results
Potential economic impact of the TC Rilem is very important and is set at two levels.
On the one hand, improving the performance of building materials is targeted. Therefore, improvement of built spaces incorporating those materials (mechanical, acoustical and thermal performances, quality of indoor air environments, environmental quality of these materials, ...) is concerned.
On the other hand, diffusion of these materials will allow development of specific production and processing channels for these materials, including
- a non-food recovery of agricultural products,
- allowing short cycle distribution of building materials since these raw materials are available quite everywhere,
- with low environmental impact (natural materials, storing CO2, easily renewable, reusable, ...).