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.

External Sulphate Attack  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 Cement paste turned into gypsum mush

External Sulphate Attack  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 Cement paste turned into gypsum mush

Acid Attack Diagnosis  Two main features  Absence of calcium hydroxide in the cement paste  Surface dissolution of cement paste exposing aggregates Calcium hydroxide depletion of cement paste. Crossed polarized light. Exposed aggregate at concrete surface. Ordinary polarized light.

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.

Porosity differences at surface of concrete viewed in fluorescent light mode.

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

Concrete Consultancy Services  Concrete Testing  Concrete, Aggregates, Cement, SCM’s, Concrete Products Permeability Tests Pipe Testing

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,