Methods of test for aggregates for concrete, Part 6: Measuring mortar-making properties of fine aggregates

IS 2386 Part 6: Scope & Key Specifications

• Scope:
  Methods for testing mortar making properties of fine aggregates for concrete. Helps assess aggregate quality relevant to concrete performance.

• Basis for Comparison:

  • Flow Table and Flow Mould per IS 1727:1960 (Pozzolanic Materials test methods).
  • Flow Table size updated: 50 mm diameter (instead of 7.06 cm).

• Tamping Bar Specifications (Clause 2.2):

  • Material: Non-absorbent, abrasion-resistant, non-brittle (e.g., rubber compound Shore A hardness 80±10 or seasoned teak wood treated with paraffin).
  • Dimensions: Cross-section 12.5 mm x 25 mm, length 125 to 150 mm.
  • Flat tamping face at right angles to length.

• Standard Reference:

  • Based on ASTM C87-62T method for mortar making properties.
  • Rounding off values per IS 2-1960.

Summary Table

flowchart LR
  A[Fine Aggregate] --> B[Test Setup]
  B --> C[Flow Table (50 mm)]
  B --> D[Tamping Bar (12.5x25 mm, 125-150 mm)]
  C --> E[Measure Flow]
  D --> E
  E --> F[Assess Mortar Making Properties]

This standard guides testing for fine aggregate suitability in mortar, ensuring concrete quality.

IS 2386 Part 6: Apparatus and Materials - Key Points

1. Flow Table & Flow Mould

   • Must conform to IS 1727:1960 (Clause 12) for pozzolanic materials testing.
   • Ensures consistency in mortar flow measurement.

2. Temperature Control

   • Mixing water, moist closet, and storage tank temperature: 27 ± 2°C (Clause 5.2).
   • Critical for consistent mortar properties.

3. Apparatus Specifications

   • Flow Table: Circular table with a diameter of about 700 mm, capable of being dropped 15 mm about 15 times in 15 seconds.
   • Flow Mould: Cylindrical, 70 mm diameter and 50 mm height, open at top and bottom.

4. Materials

   • Fine aggregate passing 2.36 mm sieve.
   • Standard cement (usually OPC) for mortar.

Summary Table: Apparatus Dimensions

Conceptual Flow Table Operation

flowchart LR
    A[Prepare Mortar] --> B[Place Mortar in Flow Mould]
    B --> C[Lift Mould Vertically]
    C --> D[Place Mould on Flow Table]
    D --> E[Drop Flow Table 15 times]
    E --> F[Measure Spread Diameter]

This ensures standardized measurement of fine aggregate mortar properties as per IS 2386 Part 6.

IS 2386 Part 6: Preparation of Mortar - Key Points

Mortar Mixing & Flow Measurement (Clauses 3.1 & 4.1)

• Water-Cement Ratio: Use 0.6 by weight.
• Mixing Sequence:
  1. Mix cement and water; allow 1 min absorption.
  2. Add saturated surface-dry sand; mix to smooth paste.
  3. Adjust sand to achieve flow of 100 ± 5%.
• Typical Quantities for 6 cubes (70 mm):
  • Cement: 1650 g
  • Water: 90 g
  • Sand: 3300 - 5500 g (depends on sand fineness)

Flow Test Procedure (Clause 4.1)

• Fill flow mould in 25 mm layers, tamp 20 times per layer.
• Level surface flush with mould top.
• Remove mould 1 min after mixing.
• Drop flow table 10 times from 12.5 mm height within 15 seconds.
• Measure average diameter increase on 4+ diameters.
• Calculate flow as:

[ \text{Flow (%)} = \frac{\text{Final Average Diameter} - \text{Original Diameter}}{\text{Original Diameter}} \times 100 ]

Acceptance Criteria

• Flow must be 100 ± 5%.
• If flow > 105%, add sand and retest.
• If flow < 95%, discard batch.
• Maximum 2 trials allowed; else prepare new batch.

flowchart TD
    A[Start: Mix Cement + Water (w/c=0.6)] --> B[Add Saturated Surface-Dry Sand]
    B --> C[Mix to Smooth Paste]
    C --> D[Fill Flow Mould in 25 mm Layers]
    D --> E[Tamp 20 times per Layer]
    E --> F[Level Surface]
    F --> G[Remove Mould after 1 min]
    G --> H[Drop Table 10 times from 12.5 mm]
    H --> I[Measure Diameter Increase]
    I --> J{Flow 100 ± 5%?}
    J -- Yes --> K[Use Mortar for Specimens]
    J -- No --> L{Flow > 105%?}
    L

Flow Test for Mortar Consistency (IS 2386 Part 6)

Key Steps & Specifications:

• Flow Table & Mould: As per IS 1727:1960 (Clause 2.1).
• Mortar Preparation (Clause 3.1):
  • Water-cement ratio = 0.6 by weight.
  • Cement absorbs water for 1 min, then mixed to smooth paste.
  • Add saturated surface-dry sand; mix until flow = 100 ± 5%.
  • Typical quantities for six 7 cm cubes:
    • Cement = 1650 g
    • Water = 90 g
    • Sand = 3300 g (fine) to 5500 g (coarse).

Flow Test Procedure (Clause 4.1):

• Fill mould in two layers, each ~25 mm thick.
• Tamp each layer 20 times with light pressure.
• Level off mortar flush with mould top.
• Lift mould 1 min after mixing.
• Drop flow table 10 times from 12.5 mm height within 15 seconds.
• Measure average diameter increase in at least 4 directions.
• Calculate flow (%) =
  [ \text{Flow} = \frac{\text{Final average diameter}}{\text{Original diameter}} \times 100 ]
• If flow > 105%, add sand and retest (max 2 trials).

Moulding Test Specimens (Clause 5.1):

• Immediately after flow test, fill 7.06 cm cube moulds in 2 layers.
• Rod each layer 25 strokes.
• Fill to overflowing, cure moist for 3-4 hours.
• Strike off surface, demould after 20-24 hours.
• Store specimens in water until testing.

flowchart TD
    A[Prepare Cement + Water (w/c=0.6)] --> B[Mix to Smooth Paste]
    B --> C[Add Saturated Dry Sand]
    C --> D[Mix to Desired Consistency (Flow 100±5)]
    D --> E[Fill Flow Mould in 2 Layers]
    E --> F[Tamp Each Layer 20 Times]
    F --> G[Level Surface & Lift Mould]
    G --> H[Drop Table 10 Times from 12.5 mm]
    H

Key Specifications & Procedures for Moulding Test Specimens (IS 2386 Part 6):

Mould Dimensions

• Cube size: 7.06 cm × 7.06 cm × 7.06 cm (Clause 2.4)

Flow Table & Flow Mould

• Follow IS 1727:1960 specifications (Clause 2.1)
• Flow mould placed centrally on the flow table.
• Mortar filled in layers (~25 mm thick), tamped 20 times per layer with uniform pressure (Clause 4.1).

Flow Test Procedure (Clause 4.1)

• After mixing, fill mould, tamp, and level surface.
• Remove mould 1 min after mixing.
• Drop table 10 times from 12.5 mm height within G seconds.
• Measure average diameter increase on 4+ diameters.
• Flow (%) = [(Final diameter - Original diameter) / Original diameter] × 100
• Target flow: 100 ± 5%
• Adjust sand content if flow is off; discard if too dry.

Specimen Surface Preparation (Clause 6.1.2)

• Surface-dry specimens.
• Remove loose sand and incrustations.
• Check bearing faces with a straight edge; grind if curvature is noticeable.
• Grinding method: rub on fine emery paper glued to a flat surface, moderate pressure.
• Discard specimens if > few hundredths mm grinding needed.

Summary Table

flowchart TD
    A[Mix Mortar] --> B[Fill Mould in Layers]
    B --> C[Tamp 20 times per layer]
    C --> D[Level Surface with Trowel]
    D --> E[Remove Mould after 1 min]
    E --> F[Drop Flow Table 10 times from 12.5 mm]
    F --> G[Measure Diameter

Curing and Storage of Specimens as per IS 2386 Part 6

• Specimen Moulds:

  • Use 7.06 cm cube moulds (Clause 2.4, 5.1).

• Specimen Preparation:

  • Place mortar in two layers, rodding each with 25 strokes.
  • Fill mould to overflowing, keep in moist closet for curing.
  • After 3-4 hours, strike off to smooth surface.
  • Remove specimens from mould after 20-24 hours (Clause 5.1).

• Curing Conditions:

  • Store specimens in water at 27 ± 2℃ (Clause 5.2).
  • Maintain moist closet and storage tank temperature at 27 ± 2℃.

• Testing Timing & Handling:

  • Test 24-hour specimens immediately after removal from moist closet.
  • Test other specimens immediately after removal from storage water.
  • Keep multiple specimens covered with damp cloth (24-hour specimens) or immersed in water at 27 ± 2℃ until testing (Clause 6.1.1).

Summary Table

flowchart TD
    A[Mixing & Flow Test] --> B[Fill 7.06 cm Moulds in 2 layers]
    B --> C[Rod each layer 25 strokes]
    C --> D[Place in Moist Closet (3-4 hrs)]
    D --> E[Strike off surface]
    E --> F[Demould after 20-24 hrs]
    F --> G[Store in Water at 27 ± 2℃]
    G --> H[Test immediately after removal]

This ensures standard curing and storage for reliable strength testing as per IS 2386 Part 6.

IS 2386 Part 6: Testing of Specimens - Key Specifications & Procedures

Specimen Preparation (Clause 6.1.2)

• Surface-dry specimens before testing.
• Remove loose sand/incrustations from faces contacting bearing blocks.
• Check specimen faces with a straight edge; if curvature is appreciable:
  • Grind lightly on fine emery paper glued to a flat surface.
  • Discard if more than a few hundredths of a millimeter grinding needed.
• Ensure moulds are clean to avoid surface irregularities.

Loading Procedure (Clause 6.1.3)

• Place specimen so loaded faces were in contact with true plane mould surfaces.
• No cushioning/bedding materials allowed.
• Apply initial load up to ½ expected max load if expected load > 2500 kg.
• Apply remaining load continuously to failure within 20 to 80 seconds.
• Do not adjust machine controls during rapid yielding before failure.

Reporting (Clause 7)

• Report compressive strength as per test results.

Summary Table: Loading Rate

Note: Proper surface preparation and controlled loading rate ensure accurate compressive strength measurement.

flowchart TD
    A[Prepare Specimen] --> B[Surface-dry & clean faces]
    B --> C{Check face flatness}
    C -->|Flat| D[Place specimen in testing machine]
    C -->|Curved| E[Light grinding or discard]
    D --> F[Apply initial load (if >2500 kg)]
    F --> G[Apply load continuously to failure (20-80s)]
    G --> H[Record compressive strength]

IS 2386 Part 6 — Reporting of Results (Clause 7.1)

• Test Specimens: Minimum of 3 specimens tested for crushing strength.
• Result Reporting: Report the average crushing strength of the specimens.
• Age of Test: Clearly specify the age (in days) of the specimen at testing.
• Loading Procedure:
  • Apply load on specimen faces that contacted true plane surfaces of mould.
  • Initial load up to ½ expected max load (if > 2500 kg) at any rate.
  • Remaining load applied continuously to failure within 20–80 seconds.
  • No adjustments during rapid yielding before failure.

Summary Table for Reporting

Additional Notes:

• No cushioning materials during testing.
• Load applied centrally below upper bearing block.
• Follow IS 1727 for flow table and mould specifications (Clause 2.1).

flowchart TD
    A[Test Specimens (≥3)] --> B[Crushing Strength Test]
    B --> C[Load Application]
    C --> D{Load Rate}
    D -->|Initial ≤ 0.5 Max Load| E[Apply at any rate]
    D -->|Remaining Load| F[Apply continuously (20-80 sec)]
    F --> G[Failure Load Recorded]
    G --> H[Calculate Average Crushing Strength]
    H --> I[Report Result + Age of Test]

This ensures standardized, reproducible reporting per IS 2386 Part 6.