IMPORTANCE OF CURING CONCRETE UNDER HOT WEATHER CONDITIONS

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IMPORTANCE OF CURING CONCRETE UNDER HOT WEATHER
CONDITIONS

• Mohammed Maslehuddin
• Research Institute, KFUPM

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Outline of Presentation

• Introduction requirements for a durable
  concrete
• Why curing
• Influence of hot weather on curing
• Methods of curing
• Concluding remarks and recommendations

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PROTECTION AGAINST REINFORCEMENT CORROSION

• Quality concrete
• Design
• Construction practices
• Protection of concrete
• Sealers
• Penetrants
• Coatings
• Protection of steel
• Inhibitors
• Coatings
• Special steels

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Factors affecting Concrete Quality
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Need for Curing

• Hydration of cement
• Cement water ? C-S-H Ca(OH)2
• Pozzolanic reaction
• Ca(OH)2 pozzolan ? C-S-H
• Minimize shrinkage
• Plastic
• Autogeneous
• Drying

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Hydration of Cement
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Effect of Humidity on Compressive Strength
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Effect of Humidity on Total Porosity
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Effect of Humidity on Chloride Permeability
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Effect of Curing on Compressive Strength
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Effect of Curing on Tensile Strength
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Effect of Curing on Flexural Strength
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Effect of Curing on Chloride Permeability
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Time to attain Strength of OPC
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Effect of Curing on Time to Corrosion
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Plastic Shrinkage
Drying
Self dessication
How to cure concrete to minimize its shrinkage
Curing membrane or fog misting
Water curing of fog misting
Impervious film
Desication must be avoided. Self desication
develops until hydration stops
Menisci formation has to be avoided
Water must be prevented from evaporating
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Autogenous Shrinkage (Type I cement)
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Autogenous Shrinkage (Silica fume cement)
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Autogenous Shrinkage in Plain and Silica Fume
Cements
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Plastic Drying Shrinkage
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Drying Shrinkage in Plain and Blended Cements
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Influence of Hot Weather on Curing
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Weather Conditions in the Arabian Gulf

• High ambient temperature (gt 40 ?C in summer).
• Low humidity (inland areas) high humidity in the
  coastal areas.
• High wind velocity.
• Increased water evaporation and drying.

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Effect of Relative Humidity on the Quantity of
Water Evaporated in Plain and Blended Cement
Concrete Specimens Exposed to a Const. Temp. of
45oC.
Quantity of water evaporated,
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Effect of Relative Humidity on Total Area of
Cracks in Plain and Blended Cement Concrete
Specimens Exposed to a Temp. of 45oC.
Total area of cracks,
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Effect of Wind Velocity on the Quantity of Water
Evaporated in Plain and Blended Cement Concrete
Specimens Exposed to a Temp. of 45oC and RH of
25.
Quantity of water evaporated,
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Effect of Temperature on Pore Size Distribution
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Effect of Curing Temperature on Total Pore Volume
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Effect of Curing Temperature on Coarse Pores
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Effect of Casting and Curing Temperature on
Concrete Quality
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Curing Methods
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Curing Methods

• Water adding techniques
• Ponding
• Spraying
• Water-retaining techniques
• Plastic sheeting
• Curing membranes
• Water-proof paper
• Steam curing, etc.

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Effect of Curing on Compressive Strength (Type I
cement)
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Effect of Curing on Compressive Strength (Silica
fume cement)
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Effect of Curing on Pulse Velocity (Type I cement)
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Effect of Curing on Pulse Velocity (Silica fume
cement)
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Drying Shrinkage (Type I and SF cements)
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Effect of Curing Methods on Chloride Permeability
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Effect of Curing on Moisture Retention
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Quality of Curing Water
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Type of Curing Water

• Water for curing shall be clean and free from
  oils, acids, alkalis, salts, organic materials or
  other materials that affect concrete properties
  or cause reinforcement corrosion.
• Does not affect the strength
• Influences reinforcement corrosion

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Requirements for Curing Water
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Concluding Remarks

• Proper curing is essential for
• Hydration of cement
• Pozzolanic reaction
• Seggration of pores
• Minimizing shrinkage strain
• Curing is critical in hot weather conditions

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Concluding Remarks (contd.)

• Wet curing by water ponding or covering with wet
  burlap is preferable.
• Minimum 7 days curing for plain cement concrete
  and early and extended curing for blended cement
  concretes is recommended.
• Avoid shrinkage by appropriate means
• Curing water should meet the chemical
  requirements.

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