Methods of test for aggregates for concrete, Part 2: Estimation of harmful materials and organic impurities

IS 2386 Part 2 - Scope: Key Formulas, Tables & Specifications

1. Scope Overview (Clause 3.5 & 4.3.2)

• Covers test procedures for determining specific gravity and water absorption of aggregates.
• Uses heavy liquids with known specific gravities to prepare mixtures for testing.

2. Heavy Liquids for Specific Gravity (Clause 4.3.2)

Use: Calculate volumes to mix liquids for desired specific gravity.

3. Sample Size Requirements

a) For Aggregates (Clause 5.3.1)

b) For Coarse Aggregate Sampling (Clause 2.3.4)

4. Typical Formula for Specific Gravity (G) Calculation

[ G = \frac{\text{Weight of oven-dry sample in air}}{\text{Weight of oven-dry sample in air} - \text{Weight of sample in water}} ]

This scope ensures accurate determination of aggregate properties critical for concrete mix design and quality control.

IS 2386 (Part 2) - Determination of Clay Lumps

Key Formula (Clause 2.5)

The percentage of clay lumps (L) in an aggregate sample is calculated as:

[ L = \frac{W - R}{W} \times 100 ]

Where:

• L = Percentage of clay lumps (%)
• W = Weight of the original sample (g or kg)
• R = Weight of the sample after removal of clay lumps (g or kg)

Reporting (Clause 2.6)

• Report the percentage of clay lumps to the nearest 0.1%.

Summary of Procedure (Clause 2.1)

• Clay lumps are separated from the aggregate sample by soaking and manual separation.
• Weigh the original sample (W).
• Remove clay lumps, dry, and weigh the remaining sample (R).
• Calculate clay lumps percentage using the formula.

Important Notes:

• Clay lumps are hard aggregates coated or impregnated with clay, affecting concrete strength.
• This test is part of routine aggregate quality control.

flowchart TD
    A[Original Aggregate Sample (W)] --> B[Soak Sample]
    B --> C[Remove Clay Lumps]
    C --> D[Weigh Remaining Sample (R)]
    D --> E[Calculate % Clay Lumps: ((W-R)/W)*100]
    E --> F[Report Results to Nearest 0.1%]

This concise method ensures aggregates meet quality standards for concrete use.

IS 2386 Part 2: Determination of Clay, Fine Silt and Fine Dust (Sedimentation Method)

Key Specifications

• Test Sample Weight (Table I):

• Sample must represent finer material proportionately.

Formula for Percentage of Clay, Fine Silt and Fine Dust

[ \text{Percentage} = \frac{1000 \times W}{0.8 \times V \times W_1} ]

Where:

• ( W ) = weight (g) of dried residue
• ( W_1 ) = weight (g) of original sample
• ( V ) = volume (ml) of pipette
• 0.8 = weight (g) of sodium oxalate per litre of diluted solution

Notes

• Particles up to 20 microns are considered.
• No correction for water-soluble salts (assumed negligible).
• Gravimetric sedimentation method depends on particle density and temperature.

flowchart TD
    A[Sample Preparation] --> B[Weigh Sample (per Table I)]
    B --> C[Disperse Sample in Solution]
    C --> D[Allow Sedimentation]
    D --> E[Withdraw Volume V with Pipette]
    E --> F[Dry Residue and Weigh (W)]
    F --> G[Calculate % Clay & Fine Silt using formula]

This method ensures accurate quantification of fine particles affecting aggregate quality.

IS 2386 Part 2: Determination of Light-weight Pieces (Coal and Lignite)

Key Specifications:

• Heavy liquid specific gravity: 2.00 ± 0.01 (Clause 4.3.2.1)
• Reporting precision: Nearest 0.1% (Clauses 3.7 & 4.7)

Calculation Formulas:

Where:

• ( L ) = % of light-weight pieces (coal & lignite)
• ( W_1 ) = Dry weight (g) of floating pieces (decanted from heavy liquid)
• ( W_2 ) = Dry weight (g) of sample portion finer than 300-micron IS sieve (for fine aggregate)
• ( W_3 ) = Dry weight (g) of sample portion coarser than 4.75-mm IS sieve (for coarse aggregate)

Summary:

• Use heavy liquid with SG = 2.00 ± 0.01 to separate light-weight pieces.
• Weigh floating pieces after decanting.
• Calculate % light-weight pieces using above formulas.
• Report results to 0.1% accuracy.

flowchart LR
    A[Sample Preparation] --> B[Separate by Size: Fine or Coarse]
    B --> C[Immerse in Heavy Liquid (SG=2.00±0.01)]
    C --> D[Decant Floating Pieces]
    D --> E[Dry and Weigh Floating Pieces (W1)]
    B --> F[Weigh Relevant Sample Portion (W2 or W3)]
    E & F --> G[Calculate % Light-weight Pieces]
    G --> H[Report Result (nearest 0.1%)]

IS 2386 Part 2 — Determination of Soft Particles

Key Points & Procedure (Clause 5.1, 5.5)

• Objective: Identify soft particles in coarse aggregates by scratch hardness.
• Test: Use a brass rod to scratch particles of each size fraction.
• Report must include:
  • Weight & number of particles tested per size.
  • Weight & number classified as soft per size.
  • Percentage of soft particles by weight and number.
  • Weighted average percentage of soft particles based on grading (excluding sizes finer than 10 mm IS sieve).

Important Specifications

• Sizes with <10% by weight (Clause 5.3.2) are not tested; soft particle % is interpolated from adjacent sizes.
• Report light-weight pieces (coal/lignite) to nearest 0.1% (Clause 4.7).

Calculation Formula for Weighted Average % Soft Particles:

[ \text{Weighted Average % Soft} = \frac{\sum (\text{Percentage of soft particles in size } i \times \text{Weight fraction of size } i)}{\sum \text{Weight fractions of sizes } \geq 10 \text{ mm}} ]

Summary Table Format for Reporting

flowchart TD
    A[Sample Aggregate] --> B[Separate by Size]
    B --> C[Test each size with brass rod]
    C --> D[Count & weigh soft particles]
    D --> E[Calculate % soft per size]
    E --> F[Compute weighted average % soft (≥10 mm)]
    F --> G[Prepare Report]

This method ensures quantification of soft particles affecting aggregate quality per IS 2386 Part 2.

IS 2386 Part 2: Estimation of Organic Impurities in Aggregates

Key Points from Clause 6.1:

• Purpose: Approximate test to detect harmful organic compounds in natural sand.
• Outcome: Indicates if further detailed testing is needed.
• Note:
  • Harmless organics may cause color but not affect strength.
  • Some harmful organics may not cause color.

General Procedure (per IS 2386 Part II):

• Mix sand sample with a solution of sodium hydroxide.
• Observe color change indicating presence of organic impurities.
• If color intensity exceeds a certain threshold, organic content is considered harmful.

Reporting:

• Presence of organic impurities is reported qualitatively (color intensity).
• For quantitative effect on mortar strength, refer IS 2386 Part VI.

Additional Notes:

• No direct formula is given in IS 2386 Part II for organic content estimation.
• The test is qualitative and indicative only.
• For quantitative assessment of organic impurities' effect, IS 2386 Part VI (Mortar Making Properties) is used.

Summary Table:

flowchart TD
    A[Sand Sample] --> B[Mix with NaOH Solution]
    B --> C{Color Change?}
    C -- Yes --> D[Indicates Organic Impurities]
    D --> E{Color Intensity > Threshold?}
    E -- Yes --> F[Further Testing Needed (IS 2386 Part VI)]
    E -- No --> G[Organic Content Acceptable]
    C -- No --> G

In brief: IS 2386 Part II provides a simple colorimetric test to detect organic impurities in sand. It is a screening test; for strength impact, IS 2386 Part VI should be referred.

IS 2386 Part 2: Sampling and Sample Preparation Key Points

1. Sample Weights for Coarse Aggregate (Clause 2.3.4)

2. Apparatus (Clause 2.2)

• Balance: Sensitive to 0.1% of sample weight.
• Containers: Allow spreading sample in a thin layer.
• Sieves: As per IS 460-1962.

3. Test Sample Weights for Clay, Fine Silt, and Dust (Clause 3.4, Table I)

4. Clay Lump Removal Procedure (Clause 2.4)

• Spread sample thinly, break clay lumps manually.
• Remove residue using sieves as below:

This ensures representative sampling and preparation for accurate aggregate testing.

IS 2386 Part 2: Apparatus & Chemicals Summary

Apparatus (Clauses 2.2, 3.2, 4.2)

• Balances:
  • Fine aggregates: ≥ 500 g capacity, sensitivity 0.1 g
  • Coarse aggregates: ≥ 5000 g capacity, sensitivity 1 g
  • General weighing: ≥ 10 kg capacity, accuracy 1 g; and ≥ 250 g capacity, accuracy 0.001 g
• Containers:
  • Watertight screw-topped glass jar (~1 kg preserving jar size)
  • Containers for drying and holding heavy liquids
• Rotating Device:
  • Rotates jar horizontally at 80 ± 20 rpm
• Sedimentation Pipette:
  • Andreason type, ~25 ml with two-way tap and scale for height measurement
• Measuring Cylinder:
  • 1000 ml capacity
• Sieves:
  • Per IS 460-1962
• Skimmer:
  • 300-micron sieve cloth for separating floating particles
• Oven:
  • Thermostatically controlled, 100–110°C

Chemicals (Clause 4.3.2)

Notes:

• Volume mixing for heavy liquids is calculated using specific gravities.
• Pipette volume is calibrated by weighing distilled water expelled.

flowchart LR
    A[Sample Preparation] --> B[Weighing (Balances)]
    B --> C[Separation using Heavy Liquids]
    C --> D[Rotating Jar @ 80±20 rpm]
    D --> E[Sedimentation Pipette Measurement]
    E --> F[Drying in Oven (100-110°C)]

This setup ensures precise measurement of aggregate properties per IS 2386 Part 2.

IS 2386 Part 2: Key Test Procedures, Formulas & Tables

1. Test Sample Preparation (Clause 3.4 & Table I)

• Sample must represent finer material proportionally.

2. Sample Weight for Different Sieve Sizes (Clause 5.3.1)

• Aggregates must be free of particles finer than 10 mm sieve.

3. Apparatus Required (Clause 3.2)

• Watertight screw-topped glass jar (~1 kg size)
• Rotating device: 80 ± 20 rpm, horizontal axis
• Andreasen sedimentation pipette (~25 ml)
• 1000 ml measuring cylinder
• Balances: 10 kg (±1 g) & 250 g (±0.001 g)
• Oven: 100-110°C, thermostatically controlled

4. General Notes

• Sedimentation pipette volume is calibrated by weighing distilled water.
• Sample sizes ensure accuracy in clay, silt, and dust content determination.
• Rotation speed controls sedimentation rate during testing.

flowchart LR
    A[Main Sample] --> B[Prepare Test Sample]
    B --> C{Max Particle Size?}
    C -->|63-25 mm| D[Take 6 kg Sample]
    C -->|20-12.5 mm| E[Take 1 kg Sample]
    C -->|10-6.3 mm| F[Take 0.5 kg Sample]
    C -->|≤4.75

IS 2386 Part 2: Calculation and Reporting of Results

Key Reporting Requirements (Clause 5.5)

• a) Weight & number of particles per size for each sample tested with brass rod.
• b) Weight & number of particles classified as soft for each size.
• c) Percentage of soft particles by weight and by number.
• d) Weighted average % of soft particles based on grading of received sample or average grading of supply (exclude sizes finer than 10 mm IS sieve).

Reporting Precision

• Organic impurities (clay, fine silt, fine dust): Nearest 0.1% (Clause 3.7).
• Light-weight pieces (coal, lignite): Nearest 0.1% (Clause 4.7).
• Clay lumps: Nearest 0.1% (Clause 2.6).

Calculation of Weighted Average % Soft Particles

[ \text{Weighted Average % Soft} = \frac{\sum (% \text{soft in size fraction} \times \text{weight fraction of that size})}{\sum \text{weight fractions}} ]

• Exclude particles finer than 10 mm sieve in calculation.

Summary Table for Reporting

flowchart TD
    A[Sample Collection] --> B[Particle Size Separation]
    B --> C[Soft Particle Test (Brass Rod)]
    C --> D[Count & Weigh Particles per Size]
    D --> E[Calculate % Soft Particles per Size]
    E --> F[Weighted Average % Soft Particles]
    F --> G[Report Results (with grading info)]

This ensures standardized, precise reporting aligned with IS 2386 Part 2 requirements.

Safety and Handling of Chemicals (IS 2386 Part 2)

Key Specifications & Safety Notes:

• Heavy liquids used for specific gravity tests include:
  • 1,1,2,2-tetrabromoethane (SG = 2.97)
  • Carbon tetrachloride (SG = 1.58)
  • Bromoform (SG = 2.88)
  • Monobromobenzene (SG = 1.49)
  • Benzene (SG = 0.88)
• Mixtures are prepared to achieve a desired specific gravity, maintained within ±0.01 during tests.

Safety Precautions:

• These chemicals are highly toxic by skin absorption and inhalation.
• Use only in a fume hood.
• Avoid skin contact and inhalation of fumes.

Mixture Volume Calculation (approximate):

To prepare a mixture with desired specific gravity ( SG_m ):

[ V_1 \times SG_1 + V_2 \times SG_2 = (V_1 + V_2) \times SG_m ]

Where:

• ( V_1, V_2 ) = volumes of liquids 1 and 2
• ( SG_1, SG_2 ) = specific gravities of liquids 1 and 2

Rearranged to find volumes for two liquids:

[ V_1 = \frac{(SG_m - SG_2)}{(SG_1 - SG_2)} \times V_{total} ]

[ V_2 = V_{total} - V_1 ]

Additional Notes:

• Bromoform-benzene mixtures: benzene can be removed by washing with water.
• Sodium oxalate solution for impurity estimation: 8 g/L stock diluted 1:10 for use.

flowchart LR
    A[Heavy Liquids] --> B[Mix to Desired SG]
    B --> C{Calculate Volumes}
    C -->|Use Formula| D[Prepare Mixture]
    D --> E[Maintain SG ±0.01]
    E --> F[Use in Hood]
    F --> G[Avoid Skin Contact & Inhalation]

Summary: Always prepare and handle heavy liquids in a fume hood, use