DEF diagnoses

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DEF diagnoses

• Four main features
• Presence of gaps completely encircling aggregates
• Wider gaps around large aggregate than around
  small aggregate
• Absence of external sulphate source
• High temperature heat curing history

Gaps around aggregate in field concrete. Railroad
sleeper. Fluorescent light.
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External Sulphate Attack
Cement paste turned into gypsum mush

• The microscopic appearance is variable.
• Features near the attacked surface
• Surface parallel cracks
• Presence of gypsum and ettringite
• Depletion of calcium hydroxide
• Decalcification of C-S-H
• Causes the paste to expand and gaps around
  aggregates are formed.
• The features present depend on many factors such
  as the quality of the concrete, exposure time,
  temperature, concentration, and chemistry of the
  water.
• develops mineralogical and chemical zoning which
  can be studied in the optical fluorescence
  microscope and the scanning electron microscope

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External Sulphate Attack
Cement paste turned into gypsum mush

• The microscopic appearance is variable.
• Features near the attacked surface
• Surface parallel cracks
• Presence of gypsum and ettringite
• Depletion of calcium hydroxide
• Decalcification of C-S-H
• Causes the paste to expand and gaps around
  aggregates are formed.
• The features present depend on many factors such
  as the quality of the concrete, exposure time,
  temperature, concentration, and chemistry of the
  water.
• develops mineralogical and chemical zoning which
  can be studied in the optical fluorescence
  microscope and the scanning electron microscope

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Acid Attack Diagnosis

• Two main features
• Absence of calcium hydroxide in the cement paste
• Surface dissolution of cement paste exposing
  aggregates

Exposed aggregate at concrete surface. Ordinary
polarized light.
Calcium hydroxide depletion of cement paste.
Crossed polarized light.
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ASR Diagnosis

• four main features
• Presence of alkali silica reactive aggregates
• Crack pattern
• Presence of alkali silica gel in cracks and/or
  voids
• Ca(OH)2 depleted paste

Gel in air void and cracks. Ordinary polarized
light.
Fluorescent light.
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Porosity differences at surface of concrete
viewed in fluorescent light mode.
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Chemical Attack

• Chemicals in many plants attack the concrete
  pastes and can lead to expansive forces or
  softening of the concrete
• The degree of attack depends on
• Type of chemical
• Concentration of the chemical
• Frequency of exposure
• Concrete porosity
• Type of cement used

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Concrete Consultancy Services

• Concrete Testing
• Concrete, Aggregates, Cement, SCMs, Concrete
  Products

Pipe Testing
Permeability Tests
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Conclusion

• Proper planning essential
• Training standards required for all tests even
  VI
• Accurate recording of data vital
• Different professions require different Equipment
• Engineering Consultants
• Crack magnifier, Cover meter (with scancar), Digi
  Schmidt
• Professional Deteriologist
• Above Ph indicator, Potentials, Resistivity,
  Pull off Tester, Porosimeter, Corrosion
  Monitoring, Impact Echo
• Contractors
• Crack magnifier, intelli-Rock Maturity Kit
• Premix Engineer
• Digi Schmidt, intelli-Rock Maturity Kit
• Precaster
• intelli-Rock Maturity Kit, Digi-Schmidt, Tico
  Ultrasonic,