Permeability of Concrete Capillary Porosity Air Void Micro Cracks Macro Cracks Aggressive deterioration Chemical Agents Corrosion of reinforcing Bars Sulphate Attacks Alkali Silica Reaction Other Causes of Distress Durability Aspects Appendix2.1

1. Bahauddin Zakariya University,Lahore Campus
Lecture#07&08
MATERIAL TESTING
REPAIR
&
MAINTENANCE
Deterioration of Concrete
Prepared by:
Engr. Shamsher Sadiq
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2. Permeability of Concrete
• Capillary Porosity
• Air Void
• Micro Cracks
• Macro Cracks
Aggressive deterioration Chemical Agents
• Corrosion of reinforcing Bars
• Sulphate Attacks
• Alkali Silica Reaction
• Other Causes of Distress
Durability Aspects
Appendix2.1
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3. Capillary Porosity:
1. Volume of Hydrated cement product >Volume of its constituents
2. As a results of hydration increased volume of hydrated gel is
eventually fills part of capillary pore volume.
3. This help in creating the discontinuity in capillary pore.
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6. Effect of curing time on capillary pores and curing time
required for various W/C Ratios
Adequately compacted & cured concrete with low W/C
Vc.p get reduced …..
becomes discontinuous coz of
expansive hydrated gel…..
which reduces the
permeability.
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7. Air voids:
Inadequate compaction form air voids
Discrete air bubbles of larger size than capillary pores.
Air voids may get interconnected by capillary system.
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8. Micro Cracks:
During service life of R.C.C structure various types of loading conditions:
Static loading
Extreme exposure conditions of temperature variations.
Micro cracking combined with capillary porosity responsible for ingress of
aggressive chemicals in R.C.C.
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13. Other Causes:
Besides above , several other factors and secondary effects would also cause
micro-crack formation , which could be severe in special structures under special
circumstances.
Initial and after care of the structure in the form of periodical painting , also plays
an important role in controlling the adverse effect due to propagation of such
micro-cracks.
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15. Aggressive deteriorating Chemical Agents:
Det. Of R.C.C is basically related with loss of water tightness of cover
concrete & Migration of aggressive chemicals through interconnected
porosity , which in turn chemically attacks on its constituents i.e.
hydrated cement gel , aggregate and the reinforcement as under:
Corrosion of reinforcing bar - Due to carbonation of concrete
Sulphate Attacks -Due to ingress of chloride
ASR
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16. Corrosion of reinforcing bars:
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19. Carbonation:
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24. Chlorides:
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26. Effect of curing time on capillary pores and curing time
required for various W/C Ratios
Adequately compacted & cured concrete with low W/C
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28. Sulphate Attack:
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30. ASR:
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32. Other Causes:
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33. Durability Aspects:
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