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What are the three primary causes of concrete degradation?
What are the three primary causes of concrete degradation?
Which of these is NOT a chemical cause of concrete degradation?
Which of these is NOT a chemical cause of concrete degradation?
Carbonation is a chemical reaction that occurs between lime and carbon dioxide.
Carbonation is a chemical reaction that occurs between lime and carbon dioxide.
True (A)
Carbonation causes a ______ in the pH of concrete.
Carbonation causes a ______ in the pH of concrete.
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What chemical is used to measure the thickness of carbonation?
What chemical is used to measure the thickness of carbonation?
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What are the two swelling composites formed by the reaction of sulfate salts with cement paste?
What are the two swelling composites formed by the reaction of sulfate salts with cement paste?
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Ettringite formation requires a cold and humid climate.
Ettringite formation requires a cold and humid climate.
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What is the most suitable analytic system for estimating sulfate attack?
What is the most suitable analytic system for estimating sulfate attack?
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What are the two types of chlorine salts used as de-icing salts?
What are the two types of chlorine salts used as de-icing salts?
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Calcium chloride can react with cement paste to create a dangerous composite called oxychloride.
Calcium chloride can react with cement paste to create a dangerous composite called oxychloride.
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What are the two main methods for estimating the chloride attack?
What are the two main methods for estimating the chloride attack?
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What is the main cause of freeze-thaw cycles?
What is the main cause of freeze-thaw cycles?
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Shrinkage can cause traction stress.
Shrinkage can cause traction stress.
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What is the maximum temperature that concrete can withstand without damage?
What is the maximum temperature that concrete can withstand without damage?
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A higher water/cement ratio is generally better for concrete.
A higher water/cement ratio is generally better for concrete.
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What is the main purpose of cement?
What is the main purpose of cement?
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What are the main characteristics of a good aggregate?
What are the main characteristics of a good aggregate?
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Admixtures used on reinforced concrete should be chloride-free.
Admixtures used on reinforced concrete should be chloride-free.
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What is the main reason why epoxy resins are used for crack sealing?
What is the main reason why epoxy resins are used for crack sealing?
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What are the three main phases in the epoxy resin injection process?
What are the three main phases in the epoxy resin injection process?
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Elastic mastics are suitable for crack sealing by injection.
Elastic mastics are suitable for crack sealing by injection.
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What are the two main types of epoxy resin injection?
What are the two main types of epoxy resin injection?
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What is the main advantage of using a low-pressure injection method for crack sealing?
What is the main advantage of using a low-pressure injection method for crack sealing?
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Vacuum injections are common for sealing cracks
Vacuum injections are common for sealing cracks
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What are the two main types of epoxy resins suggested by MAPEI?
What are the two main types of epoxy resins suggested by MAPEI?
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MAPEWRAP C UNI - AX is designed for flexural strength and shear resistance.
MAPEWRAP C UNI - AX is designed for flexural strength and shear resistance.
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What are the main advantages of using MAPELASTIC?
What are the main advantages of using MAPELASTIC?
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MAPELASTIC can be applied by hand or with a spray rendering machine.
MAPELASTIC can be applied by hand or with a spray rendering machine.
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What is the primary purpose of using MAPEFINISH?
What is the primary purpose of using MAPEFINISH?
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What are the three main products used in MAPEI's protective system for concrete?
What are the three main products used in MAPEI's protective system for concrete?
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MAPEFILL is a product that is used for anchoring steel pillars.
MAPEFILL is a product that is used for anchoring steel pillars.
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What is the main purpose of STABILCEM?
What is the main purpose of STABILCEM?
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What is the most common way to apply IDROSILEX PRONTO?
What is the most common way to apply IDROSILEX PRONTO?
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IDROSTOP is used for creating impermeable working joints.
IDROSTOP is used for creating impermeable working joints.
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What are the main types of waterproofing products offered by MAPEI?
What are the main types of waterproofing products offered by MAPEI?
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Study Notes
Concrete Degradation
- Concrete degrades due to various factors, including chemical, physical, and mechanical causes, as well as poor concrete quality.
Causes of Degradation
-
Chemical Causes:
- Carbonation: A chemical reaction between lime (created during cement hydration) and carbon dioxide in the air, forming calcium carbonate. This reduces the pH of concrete.
- Chlorine ion (CaCl₂) attack: Chlorine salts, used as de-icing agents, cause corrosion of reinforcing steel, particularly in cold climates.
- Sulphate salt attack: Sulphate salts in the ground and water react with cement paste, leading to expansion and disintegration, producing compounds like ettringite and thaumasite.
- Alkali-aggregate reaction: Reaction between cement alkalis (sodium and potassium) and reactive silica in aggregates can cause expansion and cracking in concrete.
- Acid attack: Acids can damage concrete through chemical reactions.
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Physical Causes:
- Freeze-thaw cycles: Repeated freezing and thawing of water in concrete pores expands the water, leading to cracking and deterioration.
- Shrinkage: As concrete dries, it shrinks, leading to internal stresses and surface cracking.
- High temperatures: Extreme heat can damage concrete and weaken its mechanical properties.
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Mechanical Causes:
- Abrasion: Surface wear due to friction and impact.
- Impact: Damage from physical impacts.
- Erosion: Removal of concrete due to water movement.
- Cavitation: Damage from high-speed water flow in channels with irregular surfaces.
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Bad Quality of Concrete:
- Incorrect concrete composition: Variations in water-cement ratio, gravel-cement ratio, and cement type.
- Workability problems: Impact on the properties of fresh concrete.
- Incorrect curing time: Insufficient curing or interrupted curing can result in reduced strength and durability and improper curing.
Carbonation
- Carbonation is a chemical reaction between lime and carbon dioxide present in the air.
- The chemical reaction forms calcium carbonate.
- The reduction of pH of the concrete is a consequence of this reaction.
Thickness of Carbonation
- Measurement is done using a colorimeter system.
- Phenolphthalein diluted with ethyl alcohol is used to assess the reaction.
- The absence of a colour change indicates that the concrete has been affected by the carbonation phenomenon.
Damages due to Carbonation
- Oxidation of the roads due to pH reduction from a high level (12.5-13) down to a lower value (≤ 9).
- Damage affects mainly the concrete's cover.
Alkali-aggregate Reaction
- This occurs when alkalis in cement react with certain types of aggregates.
Sulphate Attack
- Sulfate attack is a chemical deterioration mechanism.
- Ground water intrusion, sea water and construction materials.
- Chemicals reacting with cement paste.
- Swelling composites, Ettringite, and Thaumasite are produced
Chloride Attack
- Two main types: Sodium Chloride and Calcium Chloride.
- Important during winter for de-icing.
- Different types of aggression on the concrete.
Concrete Deterioration
- Deterioration due to the use of de-icing salts.
- Damage may include corrosion pitting, cracking, and spalling.
- The presence of chlorides in aggregates can lead to an alkali-aggregate reaction.
Causes of Concrete Degradation (Summary)
- Chemical: Carbonation, chlorine, sulfates, alkali-aggregate reaction, acid attack
- Physical: Freeze-thaw, shrinkage, high temperatures.
- Mechanical: Abrasion, impact, erosion, and cavitation
- Quality: Water/cement ratio, gravel/cement ratio, cement type, aggregate quality, and admixture quality.
Concrete Restoration Approach
- Identify the causes of degradation.
- Determine the extent (depth) of damage.
- Select the most appropriate restoration procedure.
- Prepare the substrate by removing damaged concrete.
Concrete Restoration Methods
- Manual demolition: Using hand tools to remove deteriorated concrete.
- Mechanical tool demolition: Using mechanical tools like sandblasting, hydrosandblasting, hydroscarification, and milling.
Reinforcement Protection
- Protective action is based on water, carbon dioxide, etc., permeability.
- Corrosion inhibitors protect the metal against oxidation.
- High alkalinity of restoration mortar promotes good adhesion to metal.
Concrete Restoration Mortars
- High adhesion
- Mechanical compatibility with existing concrete
- Controlled shrinkage
- Protection against chemical agents (carbon dioxide, chlorides, sulfates)
Crack Repair
- Crack sealing by epoxy resins injection.
- Elastic protective coverings.
Epoxy Resin Injection
- Material injection is carried out using various methods.
- Low pressure injection systems include membrane pumps or pressure vessels.
- High-pressure injection systems may require specialized cylindrical piston pumps.
MAPEI's Products for Concrete Restoration
- EPOJET
- EPORIP
- MAPELASTIC
- MAPEGROUT
- MAPEWRAP
- Additional product types include primers, waterproofing and finishing materials.
Specific Product Characteristics (Example)
-
EPOJET: Features low viscosity, workability time, and application temperature ranges. Provides high tensile, compressive strength, and modulus of elasticity.
-
EPORIP: Exhibits a different viscosity, workability time, and application temperature compared to EPOJET. Strength figures are also different in each product.
Application Examples : Different projects with various techniques for concrete remediation.
- Different projects, varied techniques: These include projects like wharf constructions, tunnel repairs, and dam restorations.
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Description
Test your knowledge on the various causes of concrete degradation including chemical, physical, and mechanical factors. Learn about interactions like carbonation and the effects of environmental elements on concrete integrity. This quiz is essential for students and professionals in construction and civil engineering.
