1. DURABILITY CONCEPT; PORE STRUCTURE
AND TRANSPORT PROCESSES
RESHMA.C
ROLL NO: 11
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2. DURABILITY CONCEPT
 The concept of ‘durability’ is difficult to quantify
 durability is not property of concrete material or a
concrete structure, but a ‘behavior’ or a performance of
concrete structure in a certain exposure condition
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3. PORE STRUCTURE
 Pore structure of concrete plays a significant role in
physical and chemical deteriorations of concrete.
 Lower porosity, smaller average pore size and lower pore
connectivity usually lead to a higher resistance of
concrete against the aggressive agents
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4. CAPILLARY PORES
 Capillary pores are assumed to have a major effect on
transport process
 capillary porosity of the cement paste depends on
 The water/cement ratio of the mix.
 The degree of hydration, which influence by the type of
cement.
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5.  Capillary pores change with time by the precipitation of
hydrates
 These precipitation processes and the nature of the C-H-
S gel leads to an extremely disordered physical structure
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7. GEL PORES
 The gel pores are interconnected interstitial spaces
between the gel particles.
 The gel pores are much smaller than the capillary pores.
 It could be contain large amount of evaporable water.
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9. TRANSPORT PROCESS
SIGNIFICANCE OF TRANSPORT PROCESS
 Transport of sulfates from external sources reaching and
reacting with aluminates to form ettringite.
 Internal diffusion of alkalis in the pore water to reactive
aggregate particle, to ‘provide’ a reactant for the alkali-
aggregate reaction
 Ingress of chloride from sea water or de-icing salts and carbon
dioxide from the air, penetrating the concrete cover,
destroying the passivity of reinforcing steel.
 Penetration of water that saturates the capillary pores fills the
air voids and freezes to causes frost damage. 9

10.  Movement of water and moisture from external and
internal sources, being absorbed by ettringite or
alkali-silica gel causing expansion ,or acting as an
obstacle to gas and vapour transport.
 Diffusion of oxygen participating in the corrosion of
process
 Drying out of moisture causing shrinkage and
shrinkage cracks.
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11. THE TRANSPORT PROCESSES
 Permeability
 Diffusion
 Electromigration
 Thermal Gradient
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12.  defined as the property of concrete which measures how
fast a fluid will flow through concrete when pressure is
applied
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13.  Diffusion is a process by which an ion can pass through
saturated concrete without any flow of water.
 Diffusion is driven by concentration gradient.
 If a strong solution is in contact with a weak solution
they will both tend towards the same concentration
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 Electromigration occurs when and an electric field
(voltage difference) is present.

15.  Thermal Gradient: Water will move from hot regions
to cold regions in solids.
 The rate at which it moves will depend on the
permeability of the solid.
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