Deleterious Materials of Aggregates
Definition: Deleterious materials in aggregates refer to substances that may adversely affect the quality, strength, and durability of the aggregate when used in construction.
Common Types of Deleterious Materials:
- Clay Lumps and Friable Particles: Weakens the concrete and reduces its durability.
- Coal and Other Lightweight Materials: Compromises the integrity and strength of the concrete.
- Mica: Increases concrete’s water demand and affects its workability.
- Organic Impurities: Stains concrete and may interfere with the cement hydration process.
- Salt Contamination: Causes efflorescence and corrosion of the reinforcement steel.
Detection Methods:
- Visual Inspection: Identifying visible impurities.
- Laboratory Tests: Such as sieve analysis, sedimentation tests, and chemical tests to quantify the presence of deleterious materials.
Impact on Concrete Properties:
- Reduction in Strength: Presence of certain deleterious materials can significantly lower concrete’s compressive strength.
- Durability Issues: Increased susceptibility to weathering, freeze-thaw cycles, and chemical attacks.
- Aesthetic Problems: Staining and uneven surface texture.
Prevention and Control:
- Source Selection: Choosing high-quality aggregate sources.
- Screening and Washing: Removing surface contaminants before using aggregates.
- Quality Control: Regular testing and monitoring of aggregate quality.
Regulatory Standards: Adhering to guidelines provided by standards such as ASTM, AASHTO, and other relevant bodies to ensure aggregate quality.
These points cover the essential aspects of deleterious materials in aggregates, their types, detection methods, impact on concrete properties, and measures for prevention and control.
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