CONCRETE SAMPLLING and Testing Procedures – IS 456:2000 & ASTM Standards

         Ensuring the quality and strength of concrete in construction projects is paramount. Proper sampling and testing procedures are essential to validate the concrete's performance. This guide delves into the standardized methods for sampling and testing concrete, referencing IS 456:2000 and ASTM standards.

📋 Sampling Procedure: 

         A random sampling procedure is adopted to ensure that each concrete batch shall have a reasonable chance of being tested i.e., sampling is done to the entire period of concreting and cover all mixing units.

Frequency:

The minimum frequency of sampling of concrete of each grade shall be accordance with the following:

Quantity of concrete in the work (m3)	Number of samples
1-5	1
6-15	2
16-30	3
31-50	4
51 and above	4 Plus one additional sample for each additional 50 m3

Source: IS 456:2000

🧪 Strength test of concrete (IS 456):

          Samples from fresh concrete shall be taken and cubes shall be made and tested at 28 days. The test strength shall be the average of the strength of 3 specimen. The individual variation should not be more than 15 percent (+15% or -15%) of the average.

📚 References

• IS 456:2000 – Code of Practice for Plain and Reinforced Concrete.​

• ASTM C31 – Standard Practice for Making and Curing Concrete Test Specimens in the Field.​

• ASTM C39 – Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens.​

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📝 Conclusion

         Adhering to standardized procedures for concrete sampling and testing is vital for ensuring the structural integrity and longevity of construction projects. By following the guidelines outlined above, engineers and construction professionals can maintain high-quality standards and compliance with regulatory requirements.

Different Grades of Concrete -- Concrete Mix Design

         Concrete grades are classifications that indicate the strength and composition of concrete mixtures. Each grade corresponds to a specific mix ratio and compressive strength, determining its suitability for various construction applications.

📊 Different grades of Concrete:

          Based on different concrete mix proportions (or) mix ratio’s, concrete mixer is divided into different grades. As per IS 456:2000, concrete mix design has the following mix proportions:

Type of Concrete	Concrete Grade	Mix Ratio (or) Proportion	Characteristic Compressive strength of Concrete @ 28 Days in N/mm2
Ordinary concrete	M5	1:5:10	5 N/mm2
	M7.5	1:4:8	7.5 N/mm2
	M10	1:3:6	10 N/mm2
	M15	1:2:4	15 N/mm2
	M20	1:1.5:3	20 N/mm2
Standard Concrete	M25	1:1:2	25 N/mm2
	M30	Design Mix	30 N/mm2
	M35	Design Mix	35 N/mm2
	M40	Design Mix	40 N/mm2
	M45	Design Mix	45 N/mm2
	M50	Design Mix	50 N/mm2
High Strength Concrete	M55	Design Mix	55 N/mm2
	M60	Design Mix	60 N/mm2
	M65	Design Mix	65 N/mm2
	M70	Design Mix	70 N/mm2

Note:-

In Example: M5

M represents "Mix"

5 represents the compressive strength achieved after 28 days of curing.

GRADES OF CONCRETE