| Summary: | Clay plays an important role in the suitability of soil for use in construction. The
affinity of a clay for moisture makes it susceptible to shrinkage and swelling on
drying and wetting and therefore problematic in terms of construction, where
stability is required for the integrity of a structure to remain intact. It is therefore
important to have methods of dealing with problematic clays in order to allow
clays to be used as a construction material. One of the methods is known as soil
stabilisation, where the properties of a soil and mainly the clay fraction are
altered to make it more suitable for its intended purpose.
The thesis investigates the use of a highly plastic clayey soil for the production
of building blocks. Due to the clayey nature and its associated properties the soil
it is not suitable in its natural state. Soil stabilisation is investigated as a method
to alter the properties of the soil. The principles of soil stabilisation are presented
as an introduction to the laboratory testing programme.
Combinations of lime, cement and fly ash are investigated as a stabilising agent.
They are investigated to determine which combination alters the properties of the
soil to such an extent, that a compressed soil block produced using the
combination and the clayey soil, would perform satisfactorily according to
accepted standards. Combinations were designed so that comparisons could be
made between blocks to determine what effect the addition of a certain stabilising
agent would have on the performance of the block in terms of the tests
conducted.
The engineering properties of the untreated soil which are not considered
suitable for use in compressed soil blocks, are significantly enhanced by he
addition of the stabilising agents. The test conducted on the blocks indicate that
the addition of 4% lime, 20% fly ash and 7% cement added to the soil produces a
block that satisfies the criteria adopted for the research and that are generally in
accord with international standards.
A mineralogical analysis was also undertaken in an attempt to identify changes in
the mineralogy of the soil, and particularly the clay, as a result of the addition of
the three stabilising agents. This analysis was done using x-ray diffraction. Due
to the nature of the clay mineral and possibly the poor crystal structure thereof,
the results were disappointing. No significant change in the clay was observed to
correlate with the results of the improved performance as indicated by the
physical tests.
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