How is RCC tested for strength and durability?

Short Answer:

RCC (Reinforced Cement Concrete) is tested for strength and durability through various field and laboratory methods. The most common strength test is the compressive strength test using concrete cubes, while durability is assessed by checking resistance to factors like water penetration, chloride attack, and carbonation.

These tests help ensure that the concrete mix meets the required design standards. Regular sampling, curing, and testing at specific intervals help in verifying that the RCC structure will remain strong and durable throughout its service life under expected loads and environmental conditions.

Detailed Explanation:

RCC tested for strength and durability

Testing RCC for strength and durability is essential to confirm that the concrete used in construction meets design expectations and remains reliable over time. RCC is a combination of concrete and reinforcing steel, and both components must be tested individually and together as a system. These tests ensure that the structure can bear loads safely and resist environmental damage such as water ingress, corrosion, and chemical attacks.

The testing is carried out at different stages—before construction (material testing), during construction (fresh concrete tests), and after construction (hardened concrete tests). Strength mainly focuses on load-bearing capacity, while durability checks long-term resistance to weather, chemicals, and wear.

Strength Testing of RCC

  1. Compressive Strength Test
    • This is the most widely used test.
    • Cube samples (usually 150 mm × 150 mm × 150 mm) are cast from fresh concrete and cured.
    • After 7 or 28 days, the cubes are crushed in a compression testing machine.
    • The average strength is calculated and compared to the design grade (e.g., M20, M25).
    • As per IS 516 and IS 456:2000.
  2. Flexural Strength Test
    • Measures the bending strength of concrete beams.
    • Important for pavements and slabs where tension develops at the bottom.
  3. Split Tensile Strength Test
    • Assesses tensile strength indirectly using cylindrical samples.
    • Helps evaluate concrete’s resistance to cracking under tension.
  4. Rebound Hammer Test (Non-destructive)
    • Measures surface hardness and gives an estimate of compressive strength.
    • Quick and used on-site without damaging the structure.
  5. Ultrasonic Pulse Velocity Test (Non-destructive)
    • Checks internal concrete quality by measuring the speed of sound waves.
    • Indicates presence of cracks, voids, or honeycombing.
  6. Pull-out Test and Core Test
    • Pull-out checks bond strength of embedded reinforcement.
    • Core samples are drilled from hardened concrete and tested for strength.

Durability Testing of RCC

  1. Water Permeability Test
    • Measures the depth and rate at which water can pass through concrete.
    • Lower permeability means better durability.
  2. Chloride Penetration Test
    • Assesses how easily chloride ions (from de-icing salts or seawater) enter the concrete.
    • Important in coastal and marine environments to avoid corrosion of steel.
  3. Carbonation Test
    • Checks how deep atmospheric CO₂ has penetrated into the concrete, which can lead to corrosion of steel.
    • A phenolphthalein indicator is used to test the depth.
  4. Sulphate Resistance Test
    • Used when concrete is exposed to sulphate-rich soils or water.
    • Measures expansion or deterioration over time.
  5. Rapid Chloride Permeability Test (RCPT)
    • Measures the electrical charge passed through concrete.
    • Lower values indicate better resistance to chloride ion penetration.

Importance of Testing

  • Confirms compliance with IS codes like IS 456, IS 516, and IS 1199
  • Ensures structure can handle design loads safely
  • Detects early signs of poor quality or deterioration
  • Reduces risk of failure and costly repairs
  • Supports long-term maintenance planning
Conclusion:

RCC is tested for strength using cube compression, flexural, and non-destructive tests, while durability is verified through permeability, chloride, and carbonation tests. These tests ensure that the structure can bear loads safely and last long under various environmental conditions. Regular and proper testing helps in achieving strong, durable, and reliable RCC construction.