Detailed information about Hardened Concrete

Hardened Concrete

Key Concepts

• Hardened Concrete Definition:

  • Concrete that has set and achieved its desired strength and form after curing for a specific period.

• Properties of Hardened Concrete:

  • Strength: Primarily compressive strength, determined by the mix design, water-cement ratio, and curing process.
  • Durability: Ability to withstand weathering, chemical attack, and wear while maintaining its integrity and performance.
  • Density: Influenced by the type and proportions of aggregate, affecting the overall mass and strength.
  • Permeability: Measure of how easily water and other substances can pass through, affecting durability and corrosion resistance.
  • Shrinkage and Creep: Long-term deformations under load, important for the structural integrity and longevity.

• Factors Affecting Properties:

  • Mix Design: Ratios of cement, water, aggregates, and admixtures.
  • Curing Conditions: Time, temperature, and humidity conditions influencing the hydration and hardening of concrete.
  • Placement and Compaction: Techniques ensuring proper consolidation and uniformity.
  • Age of Concrete: Properties evolve over time, especially during the early stages of curing.

• Testing of Hardened Concrete:

  • Compressive Strength Test: Measures the maximum load-bearing capacity in compression.
  • Flexural Strength Test: Assesses the tensile strength by measuring the stress required to bend concrete.
  • Non-Destructive Testing: Methods like ultrasonic pulse velocity and rebound hammer test for assessing the in-situ properties without damaging the structure.

• Common Issues:

  • Cracking: Can be due to shrinkage, thermal expansion, or load-induced stresses.
  • Spalling: Surface damage typically due to freeze-thaw cycles or chemical attack.
  • Efflorescence: White crystalline deposits from salts carried to the surface by water migration.

• Maintenance and Repair:

  • Surface Treatments: Sealers and coatings to protect against moisture and chemicals.
  • Patching: Repairing localized damage with suitable materials.
  • Reinforcement: Techniques to enhance structural capacity, like adding steel or composite materials.

• Applications:

  • Structural Components: Beams, columns, slabs, foundations.
  • Pavements and External Works: Roads, sidewalks, driveways.
  • Specialized Structures: Marine construction, hydraulic structures, high-performance buildings.

These notes encapsulate the essential elements for understanding the properties, factors, testing, issues, and applications associated with hardened concrete.