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Durability

Durability

Durability

Durability

Durability is the most important property of Hardened Concrete after Strength. Durability effects by:-

  1. Weathering
  2. Reaction with Aggregates
  3. Attack by Sulfates
  4. Efflorescence
  5. Reaction with Organic Chemicals
  6. Corrosion of Steel
  7. Wear

I. Weathering effect on Durability

Freeze-thaw. Length changes due to temperature change. Wetting and drying.

II. Alkali-Aggregate Reaction(AAR) effect Durability

  • Reaction of silica in aggregate with alkali in concrete cause expansion and thus stresses.
  • Generates random cracking pattern.
  • Slow 5-20 years.
  • Little or no damage with cement with alkali contents of <0.6% (most port lands).
  • Use of supplementary cementations mineral admixtures can help combat AAR by reducing amount of cement.

III. Attack by Sulfates effect Durability

  • Sulfates (SO4) of Na, K, and Mg present in water can react with concrete resulting in severe deterioration.
  • Combated by use of type 20 or 50 cement, or low permeability high density normal Portland concrete.

IV. Efflorescence effect Durability

  • White deposits on concrete due to egress of moisture with dissolved calcium hydroxide, and evaporation of water/ precipitation of Ca(OH2).
  • May be for water retaining structure or high humidity with in the structure.
  • Combated by use of dense concrete.
  • In excessive can be some durability problems.

V. Reaction with Organic Chemicals effect Durability

  • Concrete exposed to animal waste and organic acids from various industries such as dairies and wood pulp mills is sometimes damaged by surface corrosion.
  • The organic wastes may also react with the calcium hydroxide and cause expansion.
  • Reduced by good quality concrete with adequate cover of steel.
  • Essential to avoid honey comb and to design against structural cracking, low permeability, dense concrete reduces.
  • Corrosion potential.
  • Enhanced in the presence of chlorides.

VII. Wear effect Durability

  • Caused by traffic on floors and pavements and contact with running water in hydraulic structures.
  • Wear resistance is increased with increasing strength.
  • Low permeability, high density.
  • Use of aggregates with high silica contents improves wear resistance.
  • Reducing the amount of fine aggregates also reduce wear.
  • Good curing is very beneficial to wear resistance.
  • Some coatings are available to increase wear resistance.

Durability

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My name is Mustafa Awais, I am basically from Pakistan & Currently living in Saudia Arabia, I am Civil Engineer as well as Web Master.

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