Effects of Calcium Chloride on Reinforced Concrete
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Questions and Answers

Water is not an important ingredient of concrete.

False

Impurities in water may interfere with the setting of cement.

True

Sea water is suitable for mixing concrete.

False

Tap water is not acceptable for mixing concrete.

<p>False</p> Signup and view all the answers

Additive is a material which is added to the batch immediately before or during mixing.

<p>False</p> Signup and view all the answers

Admixture is a material, other than cement, water and aggregates, that is not used as an ingredient of concrete.

<p>False</p> Signup and view all the answers

One of the reasons for using chemical admixtures in concrete mixtures is to reduce the strength of concrete.

<p>False</p> Signup and view all the answers

Sea water increases the risk of corrosion of the reinforcement in reinforced concrete.

<p>True</p> Signup and view all the answers

Chemical admixtures are only used in reinforced concrete.

<p>False</p> Signup and view all the answers

Calcium chloride is suitable for use in reinforced concrete.

<p>False</p> Signup and view all the answers

Retarding admixtures are useful in concreting in cold weather.

<p>False</p> Signup and view all the answers

Sugar is a common accelerating admixture.

<p>False</p> Signup and view all the answers

Retarding action is exhibited by soluble copper salts.

<p>False</p> Signup and view all the answers

ASTM C 494-10 requires Type B admixtures to retard the initial set by at least 2 hours.

<p>False</p> Signup and view all the answers

Admixtures classified as Type D are only water-reducing.

<p>False</p> Signup and view all the answers

Water-reducing admixtures can reduce the water content of the mix by up to 20 per cent.

<p>False</p> Signup and view all the answers

The use of calcium chloride does not contribute significantly to the corrosion of steel reinforcement if concrete is well proportioned and well compacted.

<p>True</p> Signup and view all the answers

Retarding admixtures can prolong the time during which concrete can be transported and placed.

<p>True</p> Signup and view all the answers

Admixtures can be used to remedy poor quality mix ingredients.

<p>False</p> Signup and view all the answers

Admixtures are added to the concrete mix in quantities larger than 5 per cent by mass of cement.

<p>False</p> Signup and view all the answers

Superplasticizers are less effective than traditional plasticizers in reducing water content in concrete.

<p>False</p> Signup and view all the answers

The use of superplasticizers has made it possible to use high water-to-cement ratios in concrete.

<p>False</p> Signup and view all the answers

Type A admixtures are accelerating.

<p>False</p> Signup and view all the answers

Accelerating admixtures are used to slow down the early strength development of concrete.

<p>False</p> Signup and view all the answers

Superplasticizers are relatively inexpensive due to their simple manufacturing process.

<p>False</p> Signup and view all the answers

Calcium chloride is a common retarding admixture.

<p>False</p> Signup and view all the answers

Water-reducing admixtures can be used in pumped concrete or concrete placed by a tremie.

<p>True</p> Signup and view all the answers

The effectiveness of water-reducing admixtures depends only on the type of cement used.

<p>False</p> Signup and view all the answers

Admixtures are classified by their function in concrete.

<p>True</p> Signup and view all the answers

Superplasticizers increase the workability of concrete by reducing the slump.

<p>False</p> Signup and view all the answers

Type F admixtures are high-range water-reducing and retarding.

<p>False</p> Signup and view all the answers

Accelerators are beneficial in high temperatures to avoid shrinkage cracking.

<p>False</p> Signup and view all the answers

The main action of superplasticizers is to attract cement particles and increase their density.

<p>False</p> Signup and view all the answers

Water-reducing admixtures can improve the workability of concrete at a given water-to-cement ratio.

<p>True</p> Signup and view all the answers

Using an accelerator allows earlier finishing of the concrete surface and application of insulation for protection.

<p>True</p> Signup and view all the answers

Superplasticizers can be used to make high-performance concrete with strengths over 120 Mpa.

<p>True</p> Signup and view all the answers

Flowing concrete is subject to excessive bleeding or segregation.

<p>False</p> Signup and view all the answers

The normal dosage of superplasticizers is between 5 and 10 litres per cubic metre of concrete.

<p>False</p> Signup and view all the answers

Air-entraining admixtures are not used in concrete mixes.

<p>False</p> Signup and view all the answers

Damp-proofing and waterproofing admixtures are used to improve the strength of concrete.

<p>False</p> Signup and view all the answers

Workability admixtures are used to increase the strength of concrete.

<p>False</p> Signup and view all the answers

Corrosion inhibiting admixtures are used to prevent corrosion of the reinforcement in reinforced concrete.

<p>True</p> Signup and view all the answers

Fungicidal, germicidal, insecticidal admixtures are used in concrete mixes to improve its strength.

<p>False</p> Signup and view all the answers

Colouring admixtures are used to change the colour of the concrete.

<p>True</p> Signup and view all the answers

Mould releasing agents are used to improve the strength of concrete.

<p>False</p> Signup and view all the answers

Study Notes

Water in Concrete

  • Water is an important ingredient in concrete that participates in the chemical reaction with cement
  • The quality of water is important as impurities can interfere with cement setting, affect concrete strength, cause staining, and lead to corrosion of reinforcement
  • Water fit for drinking, with a pH of 6 to 8, is suitable for concrete mixing and curing
  • Sea water or water with high chloride content is not suitable for concrete as it can cause corrosion of reinforcement and efflorescence

Admixtures in Concrete

  • Admixtures are materials added to concrete to achieve specific properties
  • Chemical admixtures are added to the batch during or immediately before mixing
  • Additives are materials added during cement clinker grinding at the cement factory
  • Admixtures are used to:
    • Achieve specific properties
    • Maintain quality during mixing, transporting, placing, finishing, and curing
    • Overcome emergencies during concreting operations
    • Reduce costs
  • Properly used admixtures can be beneficial, but they are no remedy for poor mix ingredients, incorrect proportions, or poor workmanship

Types of Admixtures

  • Accelerating Admixtures:
    • Accelerate early strength development of concrete
    • Used in low-temperature concreting, precast concrete, and urgent repair work
    • May result in too high a rate of heat development and shrinkage cracking at high temperatures
  • Retarding Admixtures:
    • Delay the setting of cement paste
    • Useful in hot weather concreting to prevent cold joints
    • Prolong the time for transporting, placing, and compacting concrete
  • Water-Reducing Admixtures:
    • Reduce the water content of the mix
    • Permit reducing the water/cement ratio while retaining workability or improving workability
    • Can be used in pumped concrete or concrete placed by a tremie
  • Superplasticizers (High-Range Water Reducers):
    • Permit reducing the water content up to 30% without reducing workability
    • Allow using w/c ratios as low as 0.25
    • Useful in high-performance concrete with fly ash, slag, and silica fume
  • Other types of admixtures include:
    • Air-entraining Admixtures
    • Pozzolanic or Mineral Admixtures
    • Damp-proofing and Waterproofing Admixtures
    • Gas forming Admixtures
    • Air-detraining Admixtures
    • Alkali-aggregate Expansion Inhibiting Admixtures
    • Workability Admixtures
    • Corrosion Inhibiting Admixtures
    • Bonding Admixtures
    • Fungicidal, Germicidal, Insecticidal Admixtures
    • Colouring Admixtures
    • Concrete Curing Compounds
    • Polymer Bonding Agents
    • Polymer Modified Mortar for Repair and Maintenance
    • Mould Releasing Agents
    • Protective and Decorative Coatings
    • Installation Aids
    • Floor Hardeners and Dust-proofers
    • Non-shrink High Strength Grout

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Description

This quiz explores the role of calcium chloride in concrete and its impact on steel reinforcement, including corrosion and setting delays.

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