Simplified Guide to IS 2386 (Part I) - 1963: Methods of Test for Aggregates for Concrete - Particle Size and Shape

This guide explains IS 2386 (Part I) - 1963, the Indian Standard for testing aggregates for concrete, focusing on particle size and shape, in a clear and concise manner for students and engineers. It includes examples, procedures, and references to clarify the test methods. Due to OCR errors and truncated sections in the provided document, this guide uses reliable information and standard industry knowledge to address gaps.

Why This Standard Matters

IS 2386 (Part I) - 1963, adopted by the Bureau of Indian Standards (BIS) on 22 August 1963 (reaffirmed 2002, with amendments up to December 2010), specifies test methods for assessing the particle size and shape of aggregates used in concrete. These properties affect concrete’s workability, strength, and durability, making this standard critical for construction projects like buildings, bridges, and pavements.

Key Benefit: The standard provides standardized procedures to ensure aggregates meet quality requirements, enabling reliable concrete production. It aligns with international standards (e.g., British Standards Institution, American Society for Testing and Materials) and local practices.

References: [IS 2386 (Part I) - 1963, Foreword, Page 7; Clause 1, Page 8]

Key Sections Explained

1. Scope: What’s This About?

This standard covers five test methods for aggregates used in concrete:

Sieve Analysis: Determines particle size distribution of fine, coarse, and all-in aggregates.
Materials Finer than 75-Micron: Measures the quantity of fine particles (e.g., clay, silt) passing the 75-micron sieve by washing.
Flakiness Index: Assesses the percentage of flat particles in coarse aggregates.
Elongation Index: Assesses the percentage of elongated particles in coarse aggregates.
Angularity Number: Measures the angularity of coarse aggregates, affecting workability.

Example for Students: These tests are like checking the size and shape of ingredients in a recipe to ensure the concrete “mix” works well.
Example for Engineers: Use these tests to select aggregates for an M40 grade concrete bridge deck, ensuring proper grading and shape for strength and workability.

Reference: [IS 2386 (Part I) - 1963, Clause 1.1, Page 8]

2. Foreword: Context and Purpose

The standard, developed by the Cement and Concrete Sectional Committee (BDC 2), addresses the critical role of aggregate quality in concrete performance. It is part of an eight-part series (IS 2386:1963) covering various aggregate tests (e.g., deleterious materials, specific gravity, soundness). The tests in Part I help assess particle size and shape, which influence concrete mix design and performance.

Key Features:

Aligns with international standards (e.g., BSI, ASTM).
Uses the latest version of referenced standards (e.g., IS 460-1962 for test sieves).
Numerical values are rounded per IS 2:1960.
Focuses on technical provisions, not contractual details.

Example: The standard ensures aggregates for a dam project have the right size and shape to prevent issues like poor workability or weak concrete.

Reference: [IS 2386 (Part I) - 1963, Foreword, Pages 7–8]

3. Sieve Analysis (Clause 2)

Object: Determines the particle size distribution of fine, coarse, and all-in aggregates by sieving.

Apparatus:

Sieves (per IS 460-1962):
- Coarse aggregates: Square hole, perforated plate (80 mm to 4.75 mm).
- Fine aggregates: Wire cloth (3.35 mm to 75 micron).
- Sizes listed in Table I (e.g., 80 mm, 63 mm, 4.75 mm, 600 micron, 75 micron).
Balance: Accurate to 0.1% of the test sample weight.

Sample:

Minimum weights (Table II):
- 63 mm: 50 kg
- 40 mm: 25 kg
- 20 mm: 5 kg
- 4.75 mm: 0.2 kg
Prepare by quartering or using a sample divider.

Procedure:

Dry the sample (air-dry or at 100–110°C).
Weigh the air-dry sample.
Sieve successively starting with the largest sieve, shaking each for at least 2 minutes with varied motions (backwards, forwards, circular, jarring).
Avoid forcing material through sieves; gentle finger pressure or light brushing (camel hair brush for 150/75-micron sieves) is allowed.
Weigh material retained on each sieve to 0.1% accuracy.
Ensure retained weight per sieve does not exceed limits (Table III, e.g., 12 kg for 80-mm sieve, 450 g for 75-micron sieve).

Alternative Procedure: Cumulative sieving (weigh material passing each sieve) for routine purposes.
Mechanical Sieving: Requires at least 10 minutes per test.

Reporting:

Cumulative percentage passing each sieve (nearest whole number) or percentage retained between consecutive sieves (nearest 0.1%).
Graphical recording on a sieve analysis chart (Fig. 1).

Example for Students: Sieve analysis is like sorting sand and gravel into different size groups to see what’s in the mix.
Example for Engineers: Use sieve analysis to confirm coarse aggregate for a pavement meets IS 383:2016 grading requirements (e.g., 90–100% passing 20-mm sieve for medium-size aggregate).

References: [IS 2386 (Part I) - 1963, Clauses 2.1–2.6, Pages 8–12; Tables I–III, Page 9]

4. Determination of Materials Finer than 75-Micron (Clause 3)

Object: Measures the total quantity of material (e.g., clay, silt) finer than 75-micron by washing, as these affect concrete’s strength and workability.

Apparatus:

Balance: Accurate to 0.1% of sample weight.
Sieves: Nested 75-micron and 1.18-mm IS sieves.
Container: For agitation with water.
Oven: Maintains 110 ± 5°C.

Sample:

Minimum weights based on maximum nominal size:
- 4.75 mm: 500 g
- 10 mm: 1000 g
- 20 mm: 2000 g
- 40 mm or larger: 5000 g
Ensure sufficient moisture to prevent segregation.

Procedure:

Dry the sample to constant weight at 110 ± 5°C, weigh to 0.1% accuracy.
Place in a container, add water, and agitate vigorously to separate particles finer than 75-micron.
Pour wash water over nested sieves (1.18-mm over 75-micron) until clear.
Return retained material to the sample, dry to constant weight at ≤110°C, and weigh.
Calculate percentage finer than 75-micron:
[
A = \frac{B - C}{B} \times 100
]
where ( A ) = percentage finer, ( B ) = original dry weight, ( C ) = dry weight after washing.

Example for Students: This test is like washing sand to remove fine dust that could weaken concrete.
Example for Engineers: Ensure fine aggregate for a foundation has ≤3% material finer than 75-micron (per IS 383:2016, Table 2) to avoid excessive water demand.

Reference: [IS 2386 (Part I) - 1963, Clauses 3.1–3.5, Pages 12–15]

5. Determination of Flakiness Index (Clause 4, Amended 1983, 1991, 1997)

Object: Measures the percentage by weight of flat particles in coarse aggregates (≥6.3 mm), as flaky particles reduce concrete durability.

Apparatus:

Balance: Accurate to 0.1% of sample weight.
Metal Gauge: Thickness gauge with elongated slots (Fig. 2, tolerances: ±0.2 mm for ≥50 mm, ±0.1 mm for <50 mm).
Sieves: Sizes per Table V (e.g., 63 mm to 6.3 mm).

Sample: Minimum 200 pieces per size fraction.

Procedure:

Sieve the sample per Clause 3 using Table V sieves.
Gauge each fraction for thickness using the metal gauge (slot widths in Table V, e.g., 13.5 mm for 25–20 mm fraction).
Count pieces passing the gauge in each fraction and weigh the total sample per fraction.
Calculate (per Amendment No. 3, 1997):
- ( x ): Percentage of pieces passing the gauge in each fraction (by number).
- ( y ): Percentage of each fraction’s mass relative to the total sample mass (retained on 6.3-mm sieve).
- Weighted percentage: ( x \times y ) for each fraction.
- Flakiness Index: Sum of weighted percentages across all fractions.

Reporting: Report flakiness index as a percentage (sum of weighted percentages). Optionally, report weighted percentage per fraction.

Example for Students: Flaky particles are like flat pebbles that don’t pack well, making concrete weaker.
Example for Engineers: For a pavement, ensure flakiness index is ≤15% (typical project spec) to improve aggregate interlocking.

References: [IS 2386 (Part I) - 1963, Clauses 4.1–4.5, Pages 15–17; Table V, Page 17; Amendments 1–3, Pages 23–25]

6. Determination of Elongation Index (Clause 5, Amended 2010)

Object: Measures the percentage by weight of elongated particles (length >1.8 times mean dimension) in coarse aggregates (≥6.3 mm), as elongated particles affect workability.

Apparatus:

Balance: Accurate to 0.1% of sample weight.
Metal Gauge: Length gauge (Fig. 3, e.g., 64.4 mm for 40–31.5 mm fraction per Amendment No. 4).
Sieves: Sizes per Table V.

Sample: Minimum 200 pieces per size fraction.

Procedure:

Sieve the sample per Clause 3 using Table V sieves.
Gauge each fraction for length using the length gauge (dimensions in Table V, col 4).
Weigh material retained by the gauge (elongated particles) to 0.1% accuracy.
Calculate Elongation Index: Total weight of retained material as a percentage of the total sample weight.

Example for Students: Elongated particles are like long sticks that make mixing concrete harder.
Example for Engineers: For a pumpable concrete mix, keep elongation index ≤15% to ensure smooth flow.

References: [IS 2386 (Part I) - 1963, Clauses 5.1–5.5, Pages 17–18; Table V, Page 17; Amendment 4, Page 26]

7. Determination of Angularity Number (Clause 6)

Object: Measures the angularity of coarse aggregates (4.75–20 mm), which affects workability and mix design. Higher angularity means less rounded particles, requiring more binder.

Apparatus:

Metal Cylinder: ~3 liters, 15 cm diameter and height, ≥3 mm thick.
Tamping Rod: 16 mm diameter, 60 cm long, rounded at one end.
Balance: 10 kg capacity, readable to 1 g.
Scoop: ~1-liter capacity.

Calibration: Weigh water required to fill the cylinder at 27°C (no meniscus).

Sample:

Minimum 10 kg of predominant size (retained between sieve pairs: 20–16 mm, 16–12.5 mm, 12.5–10 mm, 10–6.3 mm, 4.75–6.3 mm).
Dry at 100–110°C for 24 hours, cool in an airtight container.

Procedure:

Fill the cylinder with aggregate in three layers, each tamped with 100 blows (rod falls freely from 5 cm, 2 blows/sec).
Level the third layer with the tamping rod as a straight edge.
Add individual pieces, rolling them in without force until the rod remains in contact with the cylinder’s edge.
Weigh the aggregate in the cylinder to the nearest 5 g.
Perform three determinations;