Holistic Models of concrete Deterioration/Cracking

1. Bahauddin Zakariya University,Lahore Campus
Lecture#
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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