Methods of test for aggregates for concrete, Part 3: Specific gravity, density, voids, absorption and bulking

IS 2386 Part 3: Scope & Key Specifications

1. Scope (Clause 5.5)

• Covers test methods for determination of specific gravity, water absorption, bulk density, and voids in aggregates.

2. Apparatus for Bulk Density & Voids (Clause 3.2)

• Tamping Rod: 16 mm diameter, 60 cm length, rounded end.

3. Key Calculations

Summary Diagram:

flowchart TD
    A[Aggregate Sample] --> B[Weigh SSD in Air (B)]
    A --> C[

IS 2386 Part 3: Key Formulas for Specific Gravity & Water Absorption

1. Definitions of Weights

2. Formulas (per Clauses 2.2.4, 2.3.4 & 2.4.3)

• Clause 2.2.4: [ SG = \frac{B - A}{B - C} ]
• Clause 2.3.4: [ \text{Apparent SG} = D - (A - B) ]
• Clause 2.4.3: [ \text{Apparent SG} = D - (B - C) ] | | Water Absorption (%) |
• Clause 2.2.4: [ \text{Water Absorption} = 100 \times \frac{B - C}{C} ]
• Clause 2.3.4: [ \text{Water Absorption} = 100 \times \frac{C - D}{D} ]
• Clause 2.4.3: [ \text{Water Absorption} = 100 \times \frac{A - D}{D} ] |

3. Notes:

• Saturated Surface-Dry (SSD) condition is critical for accurate water absorption measurement.
• Use oven-dried weight (D or C) as the base for percentage calculations.
• Pycnometer or gas jar is used for fine aggregates; direct weighing for coarse aggregates.

flowchart TD
    A[Oven-Dried Sample (D)] -->|Saturate| B[Saturated Surface-Dry Sample (A or B)]
    B -->|Weigh in Air| C[Weight in Air]
    B

IS 2386 Part 3: Bulk Density and Voids Determination

Key Apparatus (Clause 3.2)

• Balance: Accurate to 0.5% of sample weight.
• Cylindrical Metal Measure: Watertight, rigid, corrosion-resistant.
  • Capacity depends on largest particle size (see Table I).
• Tamping Rod: 16 mm diameter, 60 cm length, rounded end.

Table I: Container Size for Bulk Density Test

Condition of Specimen (Clause 3.4.1)

• Test on dry material for voids.
• For bulking tests, material may have specified moisture content.

Calculation of Voids (Clause 3.5)

[ \text{Percentage of voids} = \left(1 - \frac{Y}{G}\right) \times 100 ]

Where:

• ( Y ) = Bulk density (kg/litre)
• ( G ) = Specific gravity of aggregate

Reporting (Clause 3.6)

• Bulk density: Report to 0.01 kg/litre.
• Voids: Report as whole percentage.
• State aggregate condition: (a) oven dry, (b) saturated surface dry, (c) with moisture %.

This ensures accurate measurement of bulk density and voids essential for mix design and quality control.

IS 2386 (Part 3) - Determination of Bulking of Fine Aggregate (Field Method)

Key Points:

• Objective (Clause 4.1): Determine the necessary adjustment for bulking of fine aggregate in the field.
• Specimen Condition (Clause 3.4.1): Test usually on dry material; for bulking, material with moisture can be used.
• Reporting (Clause 4.4): Report bulking percentage to the nearest whole number.

Bulking of Fine Aggregate - Formula:

Bulking occurs due to moisture causing particles to separate, increasing volume.

[ \text{Bulking %} = \frac{V_w - V_d}{V_d} \times 100 ]

Where:

• (V_w) = Volume of wet sand
• (V_d) = Volume of dry sand

Typical Bulking Values (Approximate):

Note: Bulking varies with sand type and moisture.

Procedure Summary:

1. Fill a container with dry sand, level it, and record volume (V_d).
2. Add water to sand, mix, and record new volume (V_w).
3. Calculate bulking % using the formula above.
4. Adjust mix design volume of fine aggregate accordingly.

flowchart TD
    A[Start: Collect Fine Aggregate] --> B[Measure Volume of Dry Sand (Vd)]
    B --> C[Add Water to Achieve Moisture Content]
    C --> D[Measure Volume of Wet Sand (Vw)]
    D --> E[Calculate Bulking % = ((Vw - Vd)/Vd)*100]
    E --> F[Report Bulking % to Nearest Whole Number]

Remember: Bulking affects volume batching in concrete; adjust fine aggregate volume to avoid mix inconsistency.

IS 2386 Part 3: Surface Moisture in Fine Aggregate (Field Method)

Key Specifications:

• Sample size: Minimum 200 g (Clause 5.3)
• Method: Displacement of water to find surface moisture.
• Accuracy depends on: Specific gravity (G) of saturated surface-dry (SSD) fine aggregate.

Important Formulas:

Let:

• ( V_1 ) = weight of water displaced by wet sample (g)
• ( V_a ) = weight of sample / specific gravity (SSD basis)
• ( M_1 ) = weight of wet sample (g)
• ( G ) = specific gravity of SSD fine aggregate

1. Percentage surface moisture w.r.t SSD fine aggregate:

[ P_1 = \frac{V_1 - V_a}{M_1 - V_a} \times 100 ]

2. Percentage surface moisture w.r.t wet fine aggregate:

[ P_2 = \frac{M_1 - V_a}{M_1} \times 100 ]

3. Relationship involving ratio ( r ) (surface moisture weight / SSD weight):

[ 1 + r = \frac{V_3}{V_a} ]

4. Weight of sample:

[ M_1 = V_a \times G ]

Reporting:

• Report percentage bulking to nearest whole number (Clause 4.4).
• Use larger samples for higher accuracy.

Summary Diagram:

flowchart TD
    A[Collect Sample ≥ 200g] --> B[Measure Wet Weight \(M_1\)]
    B --> C[Immerse in Water to find Displaced Water Weight \(V_1\)]
    C --> D[Calculate \(V_a = \frac{M_1}{G}\)]
    D --> E[Compute Surface Moisture % using formulas \(P_1\) and \(P_2\)]
    E --> F[Report Results (Moisture %, Bulking %)]

This method provides a reliable field estimation of surface moisture critical for mix design adjustments.

IS 2386 Part 3 - Apparatus Summary

Key Apparatus and Specifications:

1. Balance:

   • Capacity: ≥ 2 to 3 kg (depending on clause)
   • Sensitivity: 0.5 g or better
   • Must allow weighing vessel with sample and water.

2. Flask / Vessel:

   • Volume: 2 to 3 times the loose volume of sample (approx. 1 to 1.25 litres for pycnometer)
   • Accuracy: Volume reading/filling within ±0.5 ml
   • Types:
     • Pycnometer with metal conical screw top and 6 mm hole (airtight with washer)
     • Wide-mouthed glass vessel with flat ground lip and plane glass disc cover
   • Material: Glass or non-corrosive metal

3. Oven:

   • Temperature: 100 to 110°C
   • Well ventilated and thermostatically controlled

4. Additional Apparatus:

   • Warm air supply (e.g., hair drier)
   • Tray (area ≥ 325 cm²)
   • Airtight container for sample storage
   • Filter papers and funnel

5. Bulk Density Cylindrical Metal Measure:

6. Tamping Rod:
   • Diameter: 16 mm
   • Length: 60 cm
   • Rounded end

Notes:

• The vessel volume should allow filling to a constant volume with ±0.5 ml accuracy.
• Balance sensitivity must be at least 0.5% of sample weight.
• Metal measures must be watertight, corrosion-resistant, and rigid.

flowchart TD
    A[Sample Preparation] --> B[Weighing on Balance]
    B -->

IS 2386 Part 3 — Sample Preparation: Key Apparatus & Specifications

Apparatus & Containers

• Glass Vessel/Jar: Wide-mouthed, ~1.25 to 1.5 litres capacity, flat ground lip, plane ground disc cover for watertight fit.
• Tray: Shallow tray, minimum area 325 cm².
• Cloths: Two dry, soft absorbent cloths, each ≥ 75 x 45 cm.
• Airtight Container: Large enough to hold the sample without spillage.
• Filter Papers & Funnel: For filtration during preparation.
• Means of Warm Air Supply: E.g., hair drier for drying samples.

Measuring & Weighing Equipment

• Balance:
  • Capacity ≥ 2 to 3 kg (depending on clause).
  • Sensitivity/accuracy ≤ 0.5 g.
  • Shape suitable for suspending sample basket (for water weighing).
• Flask/Container:
  • Glass or non-corrosive metal.
  • Volume 2 to 3 times the loose volume of the sample.
  • Volume reading accuracy within ±0.5 ml.
• Oven:
  • Thermostatically controlled.
  • Temperature range: 100 to 110°C.

Summary Table of Key Specifications

flowchart TD
    A[Sample Collection] --> B[Drying in Oven (100-110°C)]
    B --> C[Weighing on Balance (±0.5g)]
    C --> D[Measurement in Flask (±0.5 ml)]
    D --> E[Storage in Airtight Container]
    E --> F[Further Testing]
``

IS 2386 Part 3: Test Procedures for Different Aggregate Sizes

Key Methods for Specific Gravity & Water Absorption Tests

Sample Size & Preparation (Clause 2.2.2)

• Minimum 2000 g sample for aggregates > 10 mm.
• Avoid artificially heated aggregates or declare if used.
• Perform two tests on separate samples for reliability.

General Procedure Highlights (Clause 2.1 & 2.5.2)

• Remove entrapped air by stirring with a rod (for 10-40 mm aggregates) instead of jolting.
• Determine:
  • Specific Gravity (G)
  • Apparent Specific Gravity (Ga)
  • Water Absorption (%)

Typical Formula for Water Absorption:

[ \text{Water Absorption (%)} = \frac{W_{ssd} - W_{dry}}{W_{dry}} \times 100 ]

Where:

• ( W_{ssd} ) = Weight of saturated surface dry sample
• ( W_{dry} ) = Weight of oven-dried sample

Summary Diagram of Methods by Aggregate Size:

flowchart TD
    A[Aggregate Size] --> B{Size > 40 mm?}
    B -- Yes --> C[Method I: Wire Basket + Stirring]
    B -- No --> D{Size 10-40 mm?}
    D -- Yes --> E[Method I or II: Wire Basket + Stirring]
    D -- No --> F{Size < 10 mm?}
    F -- Yes --> G[Method III: Fine Aggregate Procedure]
    F -- No --> H[Method IV: Alternate Method]

Reference: IS 2386 (Part 3) - 1963, Clauses 2

IS 2386 Part 3 provides formulas for Specific Gravity, Apparent Specific Gravity, and Water Absorption of aggregates from different clauses:

Key Formulas:

Variables (Typical meanings):

• A = Weight of saturated surface-dry sample or vessel with sample + water
• B = Weight of pycnometer/gas jar/vessel with sample + distilled water or saturated surface-dry aggregate in air
• C = Weight of pycnometer/gas jar/vessel filled with distilled water only or oven-dried aggregate in air
• D = Weight of oven-dried sample
• G = Weight of saturated aggregate in water

Example (Clause 2.4.3):

• Apparent SG = ( D - (B - C) )
• Water Absorption (%) = ( 100 \times \frac{A - D}{D} )

These calculations ensure accurate determination of aggregate properties critical for concrete mix design and quality control.

flowchart TD
    A[Oven-Dried Sample (D)]
    B[Pycnometer + Sample + Water (B)]
    C[Pycnometer + Water Only (C)]
    D[Saturated Surface-Dry Sample (A)]
    
    A -->|Weight| ApparentSG

IS 2386 Part 3: Reporting of Results — Key Points

• Individual & Mean Results: Always report both individual test values and their arithmetic mean for clarity and accuracy (Clauses 2.2.5, 2.3.5, 2.4.4).

• Aggregate Grading: State the grading (size distribution) of the aggregate tested (Clauses 2.3.5, 2.4.4).

• Aggregate Size & Condition: Specify the size of the aggregate sample and whether it was artificially heated before testing (Clause 2.2.5).

• Bulking of Sand: Report the percentage bulking of sand rounded to the nearest whole number (Clause 4.4).

• Surface Moisture (Field Method): Report surface moisture content determined by the field method as per Clause 5.

Typical Reporting Format Example:

Notes:

• No direct formulas are specified for reporting; focus is on clarity and completeness.
• Use standard IS 2386 test methods for determining values before reporting.

flowchart TD
    A[Start Testing] --> B{Test Type}
    B --> C[Aggregate Size & Condition]
    B --> D[Bulk Density]
    B --> E[Grading]
    B --> F[Bulking of Sand]
    B --> G[Surface Moisture]
    C --> H[Record Size & Heating]
    D --> H
    E --> H
    F --> H
    G --> H
    H --> I[Report Individual & Mean Results]
    I --> J[Include Grading & Conditions]
    J --> K[Complete