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DURABILITY OF CONCRETE
•Durability of Portland cement concrete (according to ACI
Committee 201) is its ability to resist weathering action,
chemical attack, abrasion, or any other process of
deterioration. A durable concrete will retain its original
form, quality and serviceability when exposed to its
environment.
• General observations:
–Water is the primary agent of deterioration. It can be a cause
of many physical processes of deterioration, or it can be a vehicle
for transport of aggressive ions which cause chemical process of
deterioration.
– The movement of water in concrete is controlled by the
permeability of concrete. Permeability is the most important
indicator of durability of concrete.
– Concrete is a basic material; therefore, acidic waters are more
harmful to concrete.
Permeability of Concrete
• Permeability is the property that governs the rate of flow of
a fluid through the concrete. The rate of flow is higher
when the permeability is higher.
•Darcy’s Law:
For steady-state flow,
dq/dt = K ΔH A / L
where dq/dt = Rate of fluid flow (in in3/s or cm3/s)
K = Coefficient of permeability (in in/s or cm/s)
ΔH = Difference in pressure head (in in. or cm)
A = Surface area (in2or cm2)
L = Thickness of the concrete (in in. or cm)
Note: ΔH = ΔP / ρ
where ΔP = Pressure difference (in lbf/in2or kgf/cm2)
ρ= Density of fluid (in lbf/in3or kgf/cm3)
Permeability of Cement Paste
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