Methods of test for soils, Part 38: Compaction control test (Hilf method)

IS 2720 Part 37: Scope & Key Specifications

Scope:

• Specifies the determination of sand equivalent value of soils and fine aggregates to assess the relative proportions of clay-like fines and sand.
• Harmonized with international standards and adapted to Indian field practices.

Key Formula for Sand Equivalent (Clause 8.1):

[ \boxed{ SE = \frac{S_s}{C_s} \times 100 } ]

• SE = Sand Equivalent value (nearest 0.1)
• S_s = Sand reading (height of sand layer)
• C_s = Clay reading (height of clay suspension)

Apparatus (Clause 1.6 & Table 3):

All dimensions in millimeters.

Precision (Clause 9.1):

• Operator consistency: Three test results on the same sample should not vary more than ±4 points from their average.

Summary Diagram (Test Process):

flowchart TD
    A[Prepare soil sample] --> B[Fill cylinder with soil suspension]
    B --> C[Allow sedimentation]
    C --> D[Measure sand layer (S_s)]
    C --> E[Measure clay layer (C_s)]
    D --> F[Calculate SE = (S_s / C_s) × 100]
    E --> F

This standard ensures reliable assessment of fines in soils for engineering applications.

IS 2720 Part 37 (1976) – Definitions & Key Specifications

1. Sand Equivalent (SE) Formula (Clause 8.1)

[ \boxed{ SE = \frac{S}{C} \times 100 } ]

• S = Sand reading (Clause 7.11)
• C = Clay reading (Clause 7.10)
• SE is reported to the nearest 0.1.

2. Apparatus Dimensions (Clause 1.6 & Fig. 1)

3. **

IS 2720 Part 37 — Apparatus Specifications for Sand Equivalent Test

Key Apparatus Components & Dimensions (All in mm)

Important Assembly Notes

• Drill & tap for M6 × 0.75 - 6H, 20 mm deep for attaching drill rod & indicator.
• Use 1.

IS 2720 Part 37 - Reagents Preparation Summary

Stock Calcium Chloride Solution (Clause 4.1 & 4.1.1)

• Ingredients:

  • Calcium chloride: 480.4 g
  • Glycerine (technical grade, IS:1796-1961): 2179 g
  • Formaldehyde: 49.7 g
  • Distilled water: initially 2 L + diluted to 4 L total volume

• Preparation Steps:

  1. Dissolve 480.4 g calcium chloride in 2 L distilled water.
  2. Cool and filter through rapid filtering paper.
  3. Add 2179 g glycerine and 49.7 g formaldehyde to filtered solution.
  4. Mix thoroughly and dilute to 4 litres.

Storage (Clause 3.8)

• Use 4-litre bottles (two) for:
  • Stock solution
  • Working solution

Sieving Sample (Clause 5.1.1)

• Use 4.75-mm IS sieve with lateral, vertical motion + jarring.
• Continue until residue passing sieve ≤ 1% by mass per minute.
• Can be done by hand or mechanical means.

Specifications:

• Calcium chloride, glycerine, formaldehyde must conform to relevant IS standards (IS: 1796 for glycerine).

flowchart TD
    A[Calcium Chloride 480.4g] --> B[Dissolve in 2L distilled water]
    B --> C[Cool & Filter]
    C --> D[Add Glycerine 2179g + Formaldehyde 49.7g]
    D --> E[Mix well & Dilute to 4L]
    E --> F[Store in 4L bottle]

This ensures reagent quality and consistency per IS 2720 Part 37.

IS 2720 Part 37 — Sample Preparation Key Points

Sieving (Clause 5.1.1)

• Use a 4.75 mm IS sieve with lateral, vertical, and jarring motion.
• Continue sieving until ≤1% by mass passes the sieve in 1 minute.
• Can be done manually or mechanically; verify mechanical thoroughness by hand sieving a single layer.

Splitting/Quartering (Clause 5.2.1.4)

• Return sieved material to sample.
• Split/quarter to get the predetermined mass or volume.
• Two successive splits/quarters without adjustment should yield the correct quantity.

Moisture Conditioning (Clause 5.2.1.1)

• Damp material if needed to prevent segregation or fines loss.
• Add water carefully to keep material free-flowing.

Calcium Chloride Solution (Clause 4.2)

• Prepare working solution by diluting 90 ml stock CaCl₂ to 4 litres with distilled/demineralized water.
• Local tap water may be used if it does not affect test results (verify by comparative testing).

Summary Table for Sample Preparation

flowchart TD
    A[Start: Sample] --> B[Sieve on 4.75 mm IS Sieve]
    B -->|Residue ≤1% in 1 min| C[Return material to sample]
    C --> D[Split/Quarter to required mass/volume]
    D --> E{Is sample free-flowing?}
    E -->|No| F[Dampen sample carefully]
    E -->|Yes| G[Proceed to test]
    G --> H[Prepare CaCl₂ solution if needed]

This ensures representative, uniform samples for testing per IS 2720 Part 37.

IS 2720 Part 37: Test Procedure Key Points

1. Test Specimen Preparation

• Repeat procedures in Clauses 5.2.2.3 to 5.2.2.5 to obtain additional specimens (Clause 5.2.2.6).
• Sample separation on 4.75 mm IS Sieve by lateral & vertical motion with jarring until <1% residue passes per minute (Clause 5.1.1).

2. Apparatus Preparation (Clause 1.6 & Table 3)

IS 2720 Part 37: Calculation and Expression of Results

• Rounding Off (Clause 0.5):
  Final values must be rounded as per IS 2-1960. Generally, round to the nearest whole number or specified decimal place.

• Reading Measurements (Clause 7.12):
  If readings fall between graduations (e.g., 2-mm marks), record the higher graduation as the value.

• Example Calculation (Clause 40.9):
  Given values: 41.2, 43.8, 40.9
  Round each up to next whole number: 42, 44, 41
  Average = (42 + 44 + 41) / 3 = 42.3
  Since average is not whole, round to nearest whole number → 43 (final sand equivalent).

Summary Table for Rounding and Recording

This ensures consistent, standardized reporting of test results in sand equivalent tests as per IS 2720 Part 37.

IS 2720 Part 37: Precision and Accuracy Summary

Precision (Clause 9.1)

• An operator must demonstrate consistent test results before performing sand equivalent tests.
• Consistency criteria:
  • Perform 3 tests on the same material sample.
  • Individual results should not vary by more than ±4 points from the average of the 3 tests.

Rounding Off (Clause 0.5 & 40.9)

• Final test values must be rounded per IS 2-1960 rules.
• Example:
  • Values: 41.2, 43.8, 40.9 → rounded up to 42, 44, 41
  • Average = (42 + 44 + 41) / 3 = 42.3
  • Sand equivalent reported as 43 (rounded to nearest whole number).

Key Points:

flowchart LR
    A[Test 1] --> B[Round per IS 2-1960]
    C[Test 2] --> B
    D[Test 3] --> B
    B --> E[Calculate Average]
    E --> F{Average whole number?}
    F -- Yes --> G[Report Average]
    F -- No --> H[Round Average to nearest whole number]
    H --> G

This ensures accuracy in reporting sand equivalent values and maintains precision in operator testing.

IS 2720 Part 37 (1976) — Key Specifications & Tables for Sand Equivalent Test Report

1. Apparatus Dimensions (Clause 1.6 & Fig. 1)

2. Precision of Test (Clause 9.1)

• Operator consistency: Results from 3 tests on the same sample should not vary by more than ±4 points from the average.
• Ensures repeatability and reliability of sand equivalent values.

3. Reporting Guidelines (Clause None: 0.5)

• Final test values must be rounded as per IS 2:1960 rounding rules.
• Report should include:
  • Sample identification
  • Test method used
  • Apparatus details
  • Individual test results and average
  • Any deviations or observations

4. Summary Diagram of Apparatus Assembly

graph TD
    A[Siphon Assembly] -->|Copper tube, rubber hoses|

IS 2720 Part 37: Sand Equivalent Test Apparatus - Key Details

Apparatus Components & Dimensions (All in mm)

Key Specifications

• Drill & Tap: M6 × 0.75 - 6H thread, 20 mm deep.
• Roll Pin Guide Hole: Ø1.6 mm