About Concrete

About Concrete

Concrete is a very durable material which can be used for most types of construction. Its properties and performance are influenced by the selection of mix ingredients, mix design, placing, compaction, curing conditions, design and detailing, and interaction with service environment.The processes of degradation, such as corrosion of steel reinforcement, is therefore dependent on concrete quality as well as exposure conditions.

Law of Fives

The “Law of Fives” postulated in Europe has now been verified by empirical data many times.

The life of a concrete structure with concrete durability problems can be divided into four phases:

  1. Design, construction and concrete curing
  2. Corrosion initiation processes are underway, but propagation of damage has not yet begun.
  3. Propagating deterioration has just begun.
  4. Propagation of corrosion is advanced, with extensive damage manifesting.

One dollar extra spent in Phase A is equivalent to saving $5 remedial expenditure in Phase B, or $25 remedial expenditure in Phase C, or $125 remedial expenditure in Phase D.

Cement types according to AS 3972

Cement Types Applications
GENERAL PURPOSE:
Type GP general purpose All types of construction
Type GB General purpose blended All types of construction; curing and strength development differ from Type GP
SPECIAL PURPOSE:
Type HE, high early strength Early strength requirements, eg, cold weather and form-work removal.
Type LH, low heat Low temperature requirements, eg, hot weather and mass concreting.
Type SR, sulphate resistant High resistance to sulphates, eg, aggressive soil.
Type SL, shrinkage limited Controlled shrinkage applications

Refer to Chapter 1 of the Guide to Concrete Repair and Protection, whose content comprises:

  1. Concrete
  2. Material properties
    – Concrete quality
    – Porosity
    – Curing
    – Durability
    – Concrete properties and rebar corrosion
  3. Acknowledgements
  4. Further reading
    – Standards

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