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An Investigation Into The Feasibility Of Timber And Limecrete Composite Flooring
Young Researcher: Tobias Hodsdon email: ab8tjh@bath.ac.uk
Establishment: University of Bath
Supervisor: Dr. Peter Walker email: P.Walker@bath.ac.uk
Aims of research:
The proposed research seeks to investigate development of a composite roundwood timber and limecrete (lime concrete) suspended floor system. The work will comprise literature review of previous work, including study of the traditional and modern use of the Brettstapel method in Germany, and experimental tests on prototype composite panels.
Principally the research work will seek to establish the technical and economic feasibility of this form of construction. In the longer term results will feed into the development of design guidelines.
Description of method:
Roundwood timbers, placed alongside one another, comprise the tension element of the proposed composite suspended floor system. The timber poles will be covered with a layer of limecrete, forming the compression element of the floor. This research builds upon work using roundwood timber and conventional concrete undertaken by Gaia Architects in association with Buro Happold (reference http://www.gaiagroup.org/Research/techinv/PAS/roundpole/coce/cocere.pdf), which has shown that timber-concrete composite floors can be a structurally viable method for spans between 3m and 6m.
This work has identified a number of issues to be investigated, including:
- Optimum cut of round pole
- Lateral connection between adjacent poles
- Bond between timber and limecrete
- Optimum span
- Manufacture (in-situ or pre-cast?)
- Cost effectiveness
A literature review will centre on establishing the mix design for limecrete. Following this, and previous work at Bath, trial mixes will seek to establish the optimum limecrete mix for this application. Thereafter, a series of four 3 m span panels will be manufactured. This work is intended to take four weeks. Following a four-week period to allow lime to cure, laboratory tests will commence to investigate influence of timber pole diameter (50-120 mm), limecrete thickness (100 - 200 mm) and bonding (shear connection or friction alone) on performance. Testing simply supported panel tests will assess short-term serviceability (deflection) and ultimate (strength) limit states. This is intended to take two weeks.
The proposed research program is an important stage in the development of sustainable floor system using low-grade timber and limecrete. The work will be supported by Trada technology (technical support and timber supply), and Buro Happold (technical advice). It is also envisaged at this stage that the work will be taken forward as a final year dissertation topic, and that the proposed study will therefore provide a sound basis for this on-going work.
Benefits to Structural Engineering:
Using roundwood timber thinings and limecrete is very sustainable construction method. A waste product from well-managed plantations, roundwood thinings is a primary sustainable building material. Limecrete, a traditional form of concrete using hydraulic lime rather than cement, also offers many environmental advantages when compared to cement.
The work will investigate this alternative flooring system, viable for spans up to 6 metres. Results will provide information on the composite action of the system, and give guidance on performance.
On completion of the final year dissertation, it is intended that a set of guidelines can be developed for its use in the UK.
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