Estudo do comportamento mecânico do fosfogesso hemi-hidratado
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2016-08-19
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Universidade Federal de Goiás
Resumo
The phosphogypsum is generated from the production of the phosphogypsum acid in the fertilizer
industry and phosphate fertilizers. Studies show that phosphogypsum can be applied in areas such as
civil construction, the cement industry and agricultural sector. However this is used in low quantities.
In pavements construction, is the phosphogypsum can be used and many studies have been taken at the
Universidade Federal de Goias (UFG). In this context, the objective of this work was to study the
hemihydrate gypsum (HH) in mixtures with soil, cement and lime, in order to facilitate and expand its
use in paving. The heat treatment of dehydrate gypsum (DH) was carried out in the Goias state, thus
obtaining the phosphogypsum (HH). Three mixtures were studied: Mixture S+HH (50% soil, 50%
phosphogypsum HH); Mixture S+HH+CIM (50% soil, 41% phosphogypsum HH and 9% cement) and
Mixture S+HH+CAL (50% soil, 44% phosphogypsum HH and 6% lime). Characterisation tests were
conducted (utilising traditional methodology and the MCT methodology) and mechanical strength tests
(unconfined compressive strength – UCS and resilient modulus – RM) to obtain parameters for use in
paving. Deformability tests were also carried out, through consolidation tests, to evaluate the
stabilisation of deformation of phosphogypsum HH over time, and stability when subjected to a load in
the saturated and unsaturated conditions. In was studied the effect of bad weather conditions on the
samples through resistance tests to the simple compression in samples exposed to the elements for up to
180 days. Scanning electron microscopy tests (SEM) were performed to understand the micro structural
behaviour. In the samples that contained phosphogypsum HH there was greater UCS than the samples
that contained only soil and mixtures with the same phosphogypsum DH proportions. The mixture
S+HH+CIM obtained greater resistance and the mixtures S+HH+CAL and S+HH showed similar
results, making the use of lime unnecessary. The RM, like the UCS showed better results for the
mixture S+HH+CIM. With regards to deformability, mixture S+HH+CIM showed lower deformations
than the other mixtures and a tendency towards stabilisation in unsaturated condition, contrary to
mixtures S+HH and S+HH+CAL. During the evaluation of the effect of bad weather, mixture
S+HH+CIM showed a 15% reduction of resistance through time, 25% resistance reduction for mixture
S+HH+CAL and 50% for mixture S+HH. However, these values are still superior to mixtures using
phosphogypsum DH used in past researches. When the microstructure of the samples were evaluated,
they showed phosphogypsum DH transformed into HH; this behaviour was more consistent in the
mixture S+HH. Finally it can be concluded that mixtures containing phosphogypsum HH are viable
application in paving base layers.
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SANTOS, Thiago Lopes dos. Estudo do comportamento mecânico do fosfogesso hemi-hidratado. 2016. 164 f. Dissertação (Mestrado em Geotecnia, Estruturas e Construção Civil) - Universidade Federal de Goiás, Goiânia, 2016.