Methods of test for stabilized soils, Part 5: Determination of unconfined compressive strength of stabilized soils

IS 4332 Part 5 (1970) — Scope & Key Specifications

Scope:
This part covers the preparation, curing, and testing of stabilized soil specimens, mainly for unconfined compressive strength tests.

Key Specifications & Requirements

• Specimen Details to Report (Clause 17.2):

  • Size and shape of specimen
  • Composition of stabilized soil mixture
  • Dry density (soil + stabilizer)
  • Moisture content (as per Clause 15(c))
  • Methods of compaction and curing
  • Curing period and temperature

• Curing Temperature Tolerance:

  • ±2°C for lab/preliminary tests
  • ±5°C for site quality control (with max & min temps reported)

• Curing Method:

  • Storage in sealed tin to maintain moisture
  • Suitable for cement or lime stabilization
  • For other stabilizers, follow manufacturer guidance

• Storage Periods for Strength Testing:

  • Cement-stabilized: 3, 7, 14, 28 days
  • Rapid assessment: typically 7 days for cement
  • Other stabilizers: as per manufacturer

Specimen Mold Dimensions (Fig. 3 & 4)

Summary Diagram: Specimen Preparation & Curing Process

flowchart TD
    A[Soil + Stabilizer Mix] --> B[Compaction in Mold]
    B --> C[Specimen Storage in Sealed Tin]
    C --> D[Curing at Constant Moisture]
    D --> E[Strength Testing at 3,7,14,28 Days]
    E --> F[Report with Specimen & Test Details]

Note: Always maintain curing temperature and moisture as per the code for reliable strength results.

IS 4332 Part 5: Grouping of Soil

Soil Grouping Criteria (Clauses 2.1 & 11.1)

Key Points:

• Fine-grained soils: Mostly silts and clays, with >90% passing 2.36 mm sieve.
• Medium-grained soils: Sands and fine gravels, with >90% passing 20 mm sieve.
• Coarse-grained soils: Gravels and larger particles, with >90% passing 40 mm sieve.

Application:

• Used for classification and selection of soil specimens for unconfined compressive strength tests.
• Specimens are prepared at pre-determined dry density or constant compactive effort for consistent strength evaluation.

Summary Diagram

flowchart TD
    A[Soil Sample] --> B{Particle Size Distribution}
    B -->|≥90% passes 2.36 mm| C[Fine-Grained Soil]
    B -->|≥90% passes 20 mm| D[Medium-Grained Soil]
    B -->|≥90% passes 40 mm| E[Coarse-Grained Soil]

This grouping ensures proper test specimen preparation and reliable strength assessment in stabilized soil engineering.

IS 4332 Part 5: Apparatus for Specimen Preparation

Key Apparatus & Specifications

1. General Apparatus (Clause 12.1)

• Sieves: 20 mm (medium-grained), 40 mm (coarse-grained)
• Balance: Accuracy ±1 g
• Moulds: Steel/Cast iron, for 150 mm cubes
  • Height & face distance: 150 ± 0.2 mm
  • Interior angle: 90° ± 0.5°
  • Plane surfaces tolerance: 0.03 mm
  • Baseplate with clamps
• Trowel: Plasterer's steel
• Curing tins: 160×160×155 mm with lids and sealing tape
• Compression testing machine: Uniform stress increase ~35 kgf/cm²/min
• Palette knife: Blade ~200×30 mm
• Flat metal plates: ~200×200×3 mm (to prevent moisture loss)
• Moisture content apparatus: As per IS 4332 Part II

2. For Pre-determined Dry Density Specimens (Clause 12.2)

• Electric or pneumatic vibrating hammer
• Square/rectangular tamper (~8,000 mm² area), preferably square
• Tamper collars to limit penetration into mould to 50 mm, 100 mm, or 150 mm (Fig. 5)

3. For Constant Compactive Effort Specimens (Clause 12.3)

• Additional apparatus as per Clause 12.2

4. For Specimens Compacted to Refusal (Clause 12.4)

• Vibrating hammer
• Square tamper (~8,000 mm²)
• Straightedge: steel strip 300×25×3 mm, one beveled edge

Tamper Collar Dimensions (Fig. 5)

flowchart TD
    A[Specimen Preparation] --> B[General Apparatus]
    A --> C[Pre-determined Dry Density]
    A --> D[Constant Comp

IS 4332 Part 5 (1970) — Key Specifications & Materials

1. Specimen & Mould Dimensions (Clause 12.1)

• Cube size: 150 mm × 150 mm × 150 mm ± 0.2 mm height & face distance
• Angle between faces: 90° ± 0.5°
• Surface flatness: ≤ 0.03 mm variation
• Mould: Steel or cast iron, robust, with baseplate & clamps
• Curing tins: 160 mm × 160 mm × 155 mm deep, sealed with lids & tape

2. Testing Equipment

• Sieve sizes: 20 mm (medium-grained), 40 mm (coarse-grained)
• Balance accuracy: ±1 g
• Compression machine: Lever or proving ring type, stress rate ~35 kgf/cm²/min
• Palette knife: Blade approx. 200 mm × 30 mm
• Flat metal plates: 200 mm × 200 mm × 3 mm (to prevent moisture loss)

3. Moisture Content (Clause 7.3)

• Determined as per IS 4332 (Part II) - 1967 on interior specimen fragments.

4. Curing Conditions (Clause 17.2)

• Temperature tolerance: ±2°C (lab), ±5°C (site QC)
• Storage: Sealed tins to maintain moisture
• Curing periods: 3, 7, 14, 28 days (cement stabilization)
• Rapid assessment: 7 days for cement-stabilized specimens

Summary Table: Key Dimensions & Equipment

IS 4332 Part 5: Preparation of Specimen - Key Points

1. Specimen Coating (Clause 4.1)

• Use paraffin wax or suitable wax to coat specimens.
• Maintains constant moisture content.
• Wax should be cooled before application for easy removal.

2. Apparatus for Specimens Compacted to Refusal (Clause 12.4)

• Electric/Pneumatic Vibrating Hammer
• Square Tamper: ~8,000 mm² area (preferably square)
• Straightedge: Steel strip, 300 mm × 25 mm × 3 mm, one bevelled edge

3. Specimen Dimensions & Moulds (Clause 12.1)

• Cube Moulds: 150 mm cubes with ±0.2 mm height and face distance tolerance
• Interior faces: Plane within 0.03 mm, angles 90° ± 0.5°
• Baseplate with robust clamps
• Use 20 mm or 40 mm IS test sieve for medium/coarse soils

4. Compaction & Curing

• Use tamper with spacing collar (Fig. 5) for predetermined dry density
• Curing tins: 160×160×155 mm with lids and sealing tape
• Curing temperature tolerance: ±2°C (lab), ±5°C (site QC)
• Typical curing periods for cement-stabilized soils: 3, 7, 14, 28 days

5. Reporting Requirements (Clause 9.2)

Include:

• Specimen size & shape
• Stabilized soil composition
• Dry density & moisture content
• Compaction & curing method, period, and temperature

6. Additional Notes

• Specimens of cohesive mixtures can be removed immediately; non-cohesive may remain 24h in mould.
• Strength increases with storage; test at multiple intervals.
• Compression testing machine rate: ~35 kgf/cm²/min.

Summary Table: Specimen Mould Dimensions

Curing of Specimens as per IS 4332 Part 5 (Clauses 13.2.2, 13.3.2, 14.1):

• Initial Curing:

  • After removing the upper mould, strike off excess material level with the lower mould using a straight edge.
  • Fill surface irregularities with material from the same sample.
  • Cover mould with a metal plate.
  • Store at 27 ± 2°C until the next day.
  • Remove specimen from mould and weigh to nearest 1 g (W2).

• Further Curing:

  • Place specimen in a curing tin, invert, seal lid with tape.
  • Weigh tin + specimen to nearest 1 g.
  • Store at 27 ± 2°C for a specified period depending on stabilizer type (see Note 4).

• Curing Period Recommendations:

  • Cement-stabilized specimens: 3, 7, 14, and 28 days.
  • Rapid assessment: typically 7 days curing.
  • Moisture retention: Wax coating (cool wax) recommended to maintain constant moisture.

• Temperature Tolerance:

  • Laboratory: ±2°C.
  • Site QC testing: ±5°C (report max/min temps).

Summary Table of Curing Conditions

Important Notes:

• Wax coating helps maintain moisture.
• Specimen removal timing depends on soil cohesion.
• Report curing method, period, temperature, specimen size, and composition (Clause 9.2).

flowchart TD
    A[Prepare specimen in mould] --> B[Strike off excess material]
    B --> C[Cover with metal plate]
    C --> D[Store at 27 ± 2°C for 24 hrs]
    D --> E[Remove specimen & weigh (W2)]
    E --> F[Place specimen in curing tin]
    F --> G

IS 4332 Part 5 (1970) — Test Procedure Key Points

Specimen Preparation & Compaction

• Compaction Types:

  • To Constant Compactive Effort (Clause 12.3): Requires additional apparatus like tampers.
  • To Refusal (Clause 12.4): Requires vibrating hammer, square tamper (~8000 mm²), and steel straightedge (300×25×3 mm).

• Specimen Handling:

  • Cohesive stabilized soils can be removed immediately from mould.
  • Non-cohesive soils with stabilizers may remain 24 hrs in mould for strength gain.
  • Wax coating (cooled) is used to maintain moisture content and ease specimen removal.

Curing & Storage

• Strength increases with curing period; typical cement stabilized specimen curing times:
  • 3, 7, 14, 28 days.
• For rapid quality assessment, 7 days curing is standard.
• Temperature tolerance for curing:
  • ±2°C for lab/preliminary tests.
  • ±5°C allowed for site QC tests (record max/min temps).

Reporting Requirements (Clause 9.2)

• Include:
  • Specimen size & shape
  • Stabilized soil composition
  • Dry density & moisture content
  • Compaction & curing methods, period, temperature

Summary Table: Curing Periods for Cement-Stabilized Specimens

flowchart TD
    A[Soil + Stabilizer Mix] --> B[Specimen Preparation]
    B --> C{Compaction Type}
    C -->|Constant Effort| D[Use Tamper & Apparatus]
    C -->|To Refusal| E[Vibrating Hammer + Tamper]
    D & E --> F[Wax Coat Specimen]
    F --> G[Curing]
    G --> H{Curing Period}
    H --> I[3,7,14,28 days]
    H --> J[7 days for rapid QC]
    G --> K[Maintain Temp ±2°C (Lab), ±5°C

IS 4332 Part 5 - Key Calculations & Specifications

1. Moisture Content Determination

• As per Clause 7.3, moisture content is determined according to IS 4332 (Part II)-1967 on a representative sample from the specimen interior.

2. Specimen Preparation & Compaction

• Clause 12.3 requires additional apparatus for specimens compacted to a constant compactive effort.

3. Reporting of Results (Clause 17.2)

Reports must include:

• Size and shape of specimen
• Composition of stabilized soil mixture
• Dry density (soil + stabilizer)
• Moisture content (from Clause 7.3)
• Compaction & curing methods
• Curing period and temperature

Tolerance on curing temperature:

• ± 2℃ for lab/preliminary tests
• ± 5℃ for site quality control (with recorded max/min temps)

4. Curing & Storage Notes

• Store specimens in sealed tins to maintain moisture.
• Suitable for cement/lime stabilization; consult stabilizer manufacturers for others.
• Strength testing periods (cement-stabilized): 3, 7, 14, 28 days.
• Rapid quality check: usually at 7 days.

Typical Formula for Dry Density (ρ_d):

[ \rho_d = \frac{W_d}{V} ]

Where:

• ( W_d ) = Dry weight of specimen
• ( V ) = Volume of specimen

Summary Table: Curing Periods for Cement-Stabilized Specimens

flowchart LR
    A[Soil + Stabilizer] --> B[Compaction to constant effort]
    B --> C[Specimen Preparation]
    C --> D[Moisture Content Determination (IS 4332 Part II)]
    D --> E[Curing in sealed tins at controlled temp]
    E --> F[Strength Testing at 3,7,14,28 days]
    F --> G[Report Results with all parameters]

Reporting of Results as per IS 4332 Part 5 (1970)

Key Requirements (Clause 17.2 & 9.2):

• Include specimen size and shape.
• Composition of the stabilized soil mixture.
• Dry density of soil or soil + stabilizer.
• Moisture content (as per Clause 7.3 / 15(c)).
• Methods of compaction and curing.
• Curing period and temperature (±2℃ tolerance in lab; ±5℃ for site QC).
• Report max and min curing temperatures if tolerance is relaxed.

Notes:

• Specimens should ideally be stored in sealed tins or coated with wax to maintain moisture.
• Strength tests usually at 3, 7, 14, and 28 days; 7 days is standard for quick assessment.
• For non-cohesive soils, specimens may remain in molds for 24 hours before removal.

Important Formula (Clause 78.54)

[ \gamma_a = \frac{100 \times W_2}{A_m \times L \times (100 + m)} \quad \text{(g/cm}^3\text{)} ]

Where:

• ( W_2 ) = Weight before wax coating (g)
• ( A_m ) = Cross-sectional area for medium-grained soil (cm²)
• ( L ) = Length of specimen (cm)
• ( m ) = Moisture content (%) after curing

Summary Table for Reporting

flowchart LR
    A[Prepare Specimen] --> B{Soil Type}
    B -->|C

Precision and Accuracy per IS 4332 Part 5

Key Specifications:

• Balance (Clause 3.1.2):

  • Must be readable and accurate to 1 g for soil testing measurements.

• Calipers (Clause 3.1.10):

  • Accuracy: 0.25 mm
  • Opening:
    • ≥ 100 mm for fine-grained soils
    • ≥ 200 mm for medium-grained soils

• Rounding Off (Clause 0.4):

  • Follow IS 2-1960 for rounding numerical values in test results.
  • Ensures consistency and avoids overstatement of precision.

IS 2-1960 Rounding Rules Summary:

Practical Notes:

• Use calibrated instruments meeting these precisions to ensure test reliability.
• Record measurements with the specified accuracy before rounding.
• Rounding should not introduce errors beyond the instrument's precision.

flowchart LR
    A[Measurement] --> B[Instrument Precision]
    B --> C{Balance or Caliper?}
    C -->|Balance| D[Accuracy = 1 g]
    C -->|Caliper| E[Accuracy = 0.25 mm]
    D --> F[Rounding per IS 2-1960]
    E --> F
    F --> G[Final Reported Value]

This ensures precision and accuracy in soil testing as per IS 4332 Part 5.

Soil Classification (IS 4332 Part 5, Clauses 2.1 & 11.1):

• Fine-Grained Soils: ≥ 90% passing 2.36 mm IS sieve
• Medium-Grained Soils: ≥ 90% passing 20 mm IS sieve
• Coarse-Grained Soils: ≥ 90% passing 40 mm IS sieve

Key Specifications:

• Sample Preparation (Clause 13.2):

  • Use only material passing 20 mm sieve for medium-grained soils
  • Use only material passing 40 mm sieve for coarse-grained soils
  • Follow IS: 4332 (Part I)-1967 for specimen compaction

• Specimen Handling (Clause 9.2 & Notes):

  • Wax coating recommended to maintain moisture
  • Specimens for cement stabilization cured at ±2°C tolerance (lab) or ±5°C (site)
  • Typical curing periods: 3, 7, 14, 28 days (7 days for quick assessment)

Summary Table of Soil Grouping:

Diagram: Soil Classification Flow

flowchart TD
    A[Soil Sample] --> B{Passing % on IS Sieve}
    B -->|≥ 90% passing 2.36 mm| C[Fine-Grained Soil]
    B -->|≥ 90% passing 20 mm| D[Medium-Grained Soil]
    B -->|≥ 90% passing 40 mm| E[Coarse-Grained Soil]

This classification guides specimen preparation and testing procedures for stabilized soils under IS 4332 Part 5.

IS 4332 Part 5: Additional Apparatus for Pre-determined Dry Density

Key Specifications (Clause 12.2)

For specimens compacted to a pre-determined dry density, the following apparatus is required:

• Electric or Pneumatic Vibrating Hammer: Suitable for controlled compaction.

• Square or Rectangular Tamper (preferably square) with an area of approximately 8,000 mm² for use with the vibrating hammer.

• Tamper Collar: Rigidly attached to the shank to limit penetration into the mould:

  • 50 mm penetration limit (Fig. 5 reference)
  • 100 mm penetration limit
  • 150 mm penetration limit

Purpose

These tampers ensure consistent compaction depth and energy, critical for achieving the pre-determined dry density.

Summary Table of Tamper Sizes

Notes:

• The tamper foot area controls compactive effort per unit area.
• The penetration limit ensures uniform compaction depth.
• Use of vibrating hammer improves compaction uniformity compared to manual tamping.

flowchart LR
    A[Vibrating Hammer] --> B[Square Tamper (8,000 mm²)]
    B --> C{Penetration Limit}
    C --> D[50 mm]
    C --> E[100 mm]
    C --> F[150 mm]

This setup ensures repeatable, controlled compaction to achieve the desired dry density.

IS 4332 Part 5: Specimen Compaction to Refusal

Key Specifications:

• Material grading:
  • Medium-grained soils: Use material passing 20-mm IS sieve.
  • Coarse-grained soils: Use material passing 40-mm IS sieve.
• Preparation follows IS 4332 (Part I)-1967 guidelines.

Apparatus (Clause 12.4):

• Electric/Pneumatic Vibrating Hammer
• Square/Rectangular Tamper: ~8000 mm² area (preferably square).
• Straightedge: Steel strip, 300 mm × 25 mm × 3 mm, one edge bevelled.

Procedure Highlights:

• Specimens compacted to refusal means compacting until no further densification occurs despite additional effort.
• Use vibrating hammer with tamper for compaction.
• Straightedge used to level the surface.

Typical Formula for Dry Density (ρd):

[ \rho_d = \frac{W_s}{V} ]

Where:

• (W_s) = Weight of dry soil (g)
• (V) = Volume of specimen (cm³)

Summary Table: Sieve Size for Soil Type

flowchart TD
    A[Prepare Soil Sample] --> B[Pass through IS Sieve]
    B -->|Medium-grained| C[20 mm Sieve]
    B -->|Coarse-grained| D[40 mm Sieve]
    C --> E[Compact with Vibrating Hammer + Tamper]
    D --> E
    E --> F[Compact to Refusal (No Further Densification)]
    F --> G[Measure Dry Density and Volume]

This ensures repeatable, standardized compaction for stabilized soil specimens as per IS 4332 Part 5.