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| Titel |
Quality assessment for brick making of the bleached topsoil of Vertic Planosols in the south-western Ethiopian Highlands |
| VerfasserIn |
Mathijs Dumon, Laure Vandemeulebroeke, Kim Van Daele, Alemayehu Regassa Tolossa, Vicky Proost, Eric Van Ranst |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250073377
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| Zusammenfassung |
| Planosols are a very common soil type in Ethiopia. The Vertic Planosols of the south-western
Highlands are typical examples of duplex soils, characterized by a bleached, silty top horizon
abruptly overlying a heavy clay subsoil. The bleached topsoil material is of local economic
importance as it is extensively used for brick making. The aim of this research was to
assess the quality of locally produced bricks following Ethiopian and European
quality standards, and formulating recommendations to improve the quality of the
bricks.
After a reconnaissance field survey three brick production sites, Bore, Serbo and
Marawaa, were selected. At each site the bleached topsoil was sampled for physico-chemical
analyses and locally produced bricks were collected for further testing. The production
process, documented by interviewing locals, consists of excavating the bleached topsoil,
manual mixing with water, shaping using an ash-covered wooden mould, trimming using
an iron wire, and drying in open air. About 30,000 dried bricks are then piled up
to form a rectangular field-oven and fired for about two and a half days. It was
observed and admitted by the locals that about 10% of the produced bricks are
lost due to severe cracking and/or melting on the inside of the field oven. On the
other hand, some of the bricks on the outside of the field oven were not sufficiently
fired.
Physico-chemical (texture, total elemental chemical composition, carbonate content, total
carbon content, sulphur content, cation exchange capacity, total specific surface) and
mineralogical (XRD, DSC, thermogravimetry, dilatometry, optical microscopy) analyses
were carried out. Additionally, the locally produced bricks were physically characterised by
their dimensions, initial rate of water absorption (IRWA), water absorption after 24h and
compressive strength. Based on the observed properties for the soil material and the locally
produced bricks, mixtures of soil samples and a sand additive were made in an attempt to
improve the quality of the bricks. In addition, the effect of the moulding method was taken
into account by making both hand-moulded and pressure-moulded bricks from
both the reference soil material and the improved mixture. These new bricks were
also tested on water absorption, drying, firing and total shrinkage and compressive
strength.
The analytical results indicated the locally produced bricks are quite strong, but absorb
too much water when matched with European and Ethiopian standards. New bricks made
from the improved mixtures show a significantly lower water absorption. Compressive
strength on the other hand, is slightly reduced for these test units, but still above standard
levels. A lower variability in measured values when using pressure-moulded test units
compared to hand-moulded test units indicated the former result in a more uniform quality of
bricks. It can be concluded that the current locally applied methods and materials
produce a moderate quality brick on average, with large variation in the quality.
Use of a sandy additive, adjusting the moulding method and improving the field
oven layout to achieve a more homogeneous temperature distribution, are surely
options to improve the quality of the bricks produced from these bleached materials. |
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