Avaliação das propriedades de transporte de massa contendo adições minerais
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Data
2009-10-06
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Universidade Federal de Goiás
Resumo
The durability of reinforced concrete structures is damaged by the degrading action of the
penetration of substances in the form of gases, vapors and liquids through the pores and
cracks. It is known that water both in its pure form or containing dissolved ions such as
chloride, sulphate, carbon dioxide or oxygen ions, can compromise the durability of concrete
structures. In reinforced concrete structures at the marine environment, for example, the
towers of wind power plants, this degradation can be more intense and accelerated. Thus, in
the present study were analyzed concretes with different mineral additions (silica fume, blast
furnace slag) and water / binder ratios (0.35, 0.45 and 0.55), with the objective to verify if the
inside and cover thickness of concrete have some effect on the mechanisms of transport and
also the effect of carbonation (only for concrete with w/b equal to 0.55) in the surface layer of
concrete is important enough to make dificult the entry of aggressive agents in concrete. For
this, the following tests to evaluate the mass transport in concrete were performed: capillary
water absorption (NBR 9779:1995), water penetration under pressure (NBR 10787:1994), air
permeability (method Figg), penetrability of chloride ion (ASTM C 1202: 2009), non-steadystate
migration test (NT BUILD 492:1999). As a result, it was found that the mineral addition
used generally provided an improvement in front of the concrete mechanisms of mass
transport. In one of the properties, namely the diffusion coefficient (non-steady-state
migration) of concrete with the use of silica fume and blast furnace slag, this has been
reduced dramatically, around 11 times for the concrete with w/b equal to 0.55, when it is
compared with concrete without mineral addition. It was observed that the inner region of
concrete behaved better, in an unexpected way, than concrete cover region for some
properties (capillary absorption, water penetration under pressure, penetration of chloride
ions). From this conclusion, it can be said that the inner part of concrete is composed of
transition zones (aggregated interface / mortar) exposed to facilitate the entry of fluids, gases
and ions. About the effect of carbonation, this affected the capillary absorption and air
permeability. The results led to explain that the clogging of the pores resulting from the
product of carbonation (CaCO3), promoted the refinement of the pores, thus increasing
capillary force and, consequently, increasing the capillary absorption. However, for air
permeability this effect has damaged the passage of air through the surface layer. Finally, it
is important noting that significant correlations were found among tests that evaluated the
mechanisms of mass transport, namely, penetration of chloride ions and capillary absorption,
diffusion coefficient (non-steady-state migration) and capillary absorption, permeability air
and water penetration under pressure, penetration of chloride ions and the diffusion
coefficient.
Descrição
Palavras-chave
Concreto , Adições minerais , Sílica ativa , Escória de alto forno , Absorção capilar , Permeabilidade , Coeficiente de difusão , Migração regime não estacionário , Penetrabilidade de cloretos , Mecanismo de transporte , Concrete , Mineral addition , Silica fume , Blast furnace slag. Capillary absorption , Permeability , Diffusion coefficient , Non-steady-state migration , Penetration of chloride ions , Transport mechanism
Citação
MENDES, Marcus Vinícius Araújo da Silva. Evaluation of the mass transport containing mineral admixtures. 2009. 201 f. Dissertação (Mestrado em Engenharias) - Universidade Federal de Goiás, Goiânia, 2009.