Core Test of Hardened Concrete as per Indian Standard

Core Test of Hardened Concrete as per Indian Standard

Key Points and Concepts

1. Purpose of Core Testing:

   • Assess the compressive strength and quality of hardened concrete.
   • Verify the integrity of concrete in existing structures.

2. Standards and Guidelines:

   • Follow guidelines provided in IS 516 (1959): "Method of Tests for Strength of Concrete."
   • Refer to IS 456: "Code of Practice for Plain and Reinforced Concrete."

3. Core Sampling:

   • Cores are extracted using diamond-studded core drilling machines.
   • Standard core diameter: At least three times the nominal maximum size of the aggregate.
   • Length-to-diameter ratio of the core: Preferably between 1.0 and 2.0.

4. Testing Procedure:

   • Preparation:
     • Ensure the core ends are smooth and perpendicular to the axis.
   • Measurement:
     • Measure diameter and length of the core to calculate the aspect ratio.
   • Loading:
     • Apply load continuously and without shock.
     • Note the failure load.

5. Formula for Compressive Strength:

   $$\text{Compressive Strength}(MPa)=\frac{\text{Failure Load}(N)}{\text{Cross-sectional Area}(m{m}^2)}$$

6. Calculations:

   • Adjust for the length-to-diameter ratio if it deviates from the standard.
   • Apply correction factors for cores taken from in-place concrete.

7. Assessment:

   • Compare the test results with specified concrete strength requirements.
   • Analyze any discrepancies to determine the cause (e.g., poor compaction, inadequate curing).

8. Factors Affecting Results:

   • Moisture condition of the core.
   • Age of the concrete.
   • Method of drilling and core extraction.

9. Reporting:

   • Include details: Core identification, location, depth, dimensions, moisture condition, and failure load.
   • Provide calculated compressive strength values and any applied correction factors.

Important Formulas

• Compressive Strength Calculation:$$f_{core}=\frac{P}{A}$$Where:
  • $f_{core}$ = Compressive strength of the core (MPa)
  • $P$ = Failure load (N)
  • $A$ = Cross-sectional area of the core (mm²)

Remember to ensure that all core tests and calculations are aligned with the relevant Indian Standards to maintain accuracy and reliability in the assessment of hardened concrete.