Methods of test for determination of permeability of natural building stones
1973 Edition

Overview of Scope under IS 4348

• Specimen Dimensions (Clause 5.1):

  • Cylindrical samples
  • Size: 100 mm diameter by 100 mm length
  • Testing sets consist of three specimens

• Test Documentation (Clause 9.1): Reports should include:

  • Sample identification
  • Testing duration
  • Specimen dimensions
  • Applied pressure and temperature
  • Measured permeability coefficient at test temperature
  • Temperature-corrected permeability coefficient
  • Variation in permeability over time (rate and trend)

• Reservoir Calibration (Clause 7.1): Calibration range from 0.9 to 1.10 times actual pressure

• Rounding Protocol (Clause 0.3): Apply IS 2:1960 for rounding numerical results

Temperature Correction Formula Example

[ k_c = k_t \times \frac{T_s + 273}{T_t + 273} ]

• (k_t): permeability at test temperature (T_t) (°C)
• (T_s): standard reference temperature (usually 27°C)

flowchart TD
    A[Prepare Specimen] --> B{Specimen Size}
    B -->|100 mm diameter x 100 mm length| C[Conduct Test]
    C --> D{Test Conditions}
    D -->|Pressure & Temperature Control| E[Measure Permeability]
    E --> F[Generate Report]
    F --> G[Include Specimen ID, Duration, Size, Pressure, Temperature, Permeability]

This section summarizes the scope and key specimen testing requirements according to IS 4348.

Guidelines for Choosing Samples for Permeability Evaluation of Natural Stones

Important Clauses:

• Clause 2.1:
  Samples must represent the average true quality of the stone type or grade.

• Clause 2.2:
  Selection is carried out by the purchaser or their authorized agent directly from quarried blocks or natural rock formations.
  Sample size should be sufficient to prepare all required test specimens.

• Clause 2.3:
  When stone quality varies noticeably, multiple samples must be chosen to cover the range of characteristics.

Practical Summary Table:

Rounding Notes:

• Follow current rounding standards, typically to nearest whole number or precision warranted by testing.

flowchart TD
    A[Quarried Stone/Natural Rock] --> B[Purchaser or Authorized Agent Selects Sample]
    B --> C{Is Quality Uniform?}
    C -- Yes --> D[Select Representative Sample]
    C -- No --> E[Select Multiple Samples]
    D & E --> F[Ensure Adequate Sample Size for Specimens]

This ensures sampling represents the stone's permeability characteristics per IS 4348.

Apparatus Specifications and Configuration as per IS 4348

1. Compressed Air System (Clause 4.1)

• Use suitable compressed air cylinders or air compressors with sufficient capacity.
• Maintain pressure within ±2% of the target setpoint.
• Employ precise pressure regulators and compatible gauges.
• A single air source may serve multiple permeability cells (refer to Fig. 2).

2. Water Supply (Clause 4.2)

• Utilize clean, de-aerated water obtained by boiling and cooling.
• Store water in sealed containers filled completely to prevent air intrusion.

3. Water Reservoir (Clause 3.2)

• Constructed from metal piping, 50–100 mm diameter and approximately 500 mm length.
• Equipped with a graduated side-arm gauge glass and valves for water and air admission, drainage, and bleeding.
• Reservoir connects directly to the permeability cell (see Fig. 1 & Fig. 2).

4. Assembly Procedure (Clause 7.4)

• Secure funnel and connect permeability cell to reservoir.
• Open valves for air bleed, reservoir-to-cell connection, and drainage.
• Fill reservoir with de-aerated water until water flows from the drain valve.
• Close drain valve and fill reservoir to required level.
• Close reservoir inlet and air bleed valves.

Equipment Flow Diagram (Fig. 2 Simplified):

flowchart LR
    CA[Compressed Air Source] --> PR[Pressure Regulator & Gauge]
    PR --> PC[Permeability Cell]
    WR[Water Reservoir] --> PC
    PC --> CB[Collection Container]
    WR --> GG[Graduated Gauge Glass]
    WR --> ABV[Air Bleeder Valve]

This setup ensures precise control of air pressure and water flow necessary for accurate permeability measurements.

Water Supply Requirements for Permeability Testing (IS 4348)

1. Water Quality and Preparation (Clause 4.2)

• Use clean, de-aerated water free from dissolved air.
• De-aerate by boiling the water and allowing it to cool.
• Store water in sealed, fully filled containers to prevent air absorption and agitation.

2. Reservoir Design (Clause 3.2)

• Metal pipe reservoir dimensions:
  • Diameter: 50 to 100 mm
  • Length: about 500 mm
• Features include graduated side-arm gauge glass and valves for water/air admission, drainage, and bleeding.
• Calibration constant for volume measurement is based on gauge divisions.

3. Filling and Calibration Procedure (Clause 7.1.1)

• Fill reservoir and purge air through the drain valve.
• Refill above zero mark on the gauge.
• Apply air pressure and adjust water level to zero by briefly opening the drain valve.
• Collect water in known increments (e.g., 250 ml) and record gauge readings for volume calculations.

4. Compressed Air Supply (Clause 4.1)

• Cylinders or compressors with pressure regulation within ±2%.
• Sensitive pressure gauges matched to regulators.
• Common air source can operate multiple testing cells.

Calibration Formula:

[ \text{Volume} = \text{Gauge divisions} \times \text{Calibration constant (ml/division)} ]

Setup Diagram (Fig. 2):

graph LR
  A[Compressed Air Source] --> B[Pressure Regulator & Gauge]
  B --> C[Air Bleeder Valve]
  C --> D[Water Reservoir with Gauge]
  D --> E[Permeability Cell]
  E --> F[Collection Vessel]

This arrangement guarantees accurate water and air pressure regulation during permeability tests.

Specifications and Preparation of Test Samples as per IS 4348

Specimen Size (Clause 5.1)

• Cylindrical shape
• Dimensions: 100 mm diameter × 100 mm length
• Each test set includes three specimens

Specimen Preparation (Clause 5.2)

• Use core drilling or comparable methods avoiding fractures; hammering is prohibited.
• Ends must be ground flat and plane using water and abrasive materials like carborundum or emery on a cast iron lap.
• The specimen axis should be perpendicular to natural stratification planes.
• Electrical polishing machines are recommended for effective surface finishing.

Test Water (Clause 4.2)

• Employ clean, de-aerated water (boiled and cooled).
• Store in sealed, fully filled containers to minimize air contact and disturbance.

Reporting Requirements (Clause 9.1)

Include for each specimen:

• Identification mark
• Testing duration
• Specimen dimensions
• Applied pressure and temperature
• Permeability coefficient at test and standardized temperatures
• Trends of permeability variation over time (direction and rate)

Summary Table for Specimens

flowchart TD
    A[Collect Sample] --> B[Core Drill Specimen]
    B --> C[Cut to 100x100 mm]
    C --> D[Grind & Polish Ends]
    D --> E[Specimen Ready for Testing]
    E --> F[Conduct Permeability Test with De-aerated Water]
    F --> G[Record Results and Prepare Report]

This ensures specimen uniformity and test reliability in accordance with IS 4348.

Key Points on Test Pressure as per IS 4348

1. Pressure Head (Clause 6.1)

• The test pressure head is set at 1.1 times the actual hydraulic head expected in service.
• Reservoir calibration spans 0.9 to 1.10 times the actual pressure (Clause 7.1).

2. Pressure Regulation (Clause 4.1)

• Use a compressed air supply regulated within ±2% of the desired pressure.
• Employ sensitive pressure gauges compatible with regulators.
• A common air source may supply multiple test cells (see Fig. 2).

3. Testing Procedure (Clause 7.5)

• Fill the system with de-aerated water.
• Apply the specified test pressure.
• Record initial gauge readings and collect outflow in a weighed container.
• Continue until steady state flow is established (inflow equals outflow).
• Maintain testing for approximately 100 hours beyond steady state to average outflows.

4. Preconditioning

• Preheat the permeability cell at 30–35°C for 24 to 30 hours before specimen placement to ensure proper sealing.

Summary Table: Pressure Parameters

flowchart LR
    A[Compressed Air Supply] --> B[Pressure Regulator ±2%]
    B --> C[Water Reservoir at 1.1 × Actual Pressure]
    C --> D[Permeability Cell]
    D --> E[Collection Bottle (Weighed)]
    E --> F[Measure Outflow & Gauge Readings]
    F --> G{Has Steady State Been Reached?}
    G -- No --> F
    G -- Yes --> H[Continue Testing for 100 Hours]
    H --> I[Calculate Average Flow Rate]

This approach simulates realistic hydraulic loading and ensures trustworthy permeability results.

Essential Steps in Permeability Testing as per IS 4348

1. Water Use (Clause 4.2)

• Employ clean, de-aerated water, prepared by boiling and cooling.
• Store water in sealed, fully filled containers to avoid air uptake and agitation.

2. Temperature Control (Clause 7.6)

• Maintain test temperature at 27 ± 3°C for consistency.

3. Reporting (Clause 9.1)

Include in the test documentation:

• Specimen identifier
• Test duration
• Specimen size
• Applied pressure
• Test temperature
• Permeability coefficient at test temperature
• Corrected permeability coefficient at standard temperature
• Time-dependent permeability changes (trend and rate)

4. Rounding Off

• Round numerical results in accordance with IS 2-1960 standards.

Additional Recommendations:

• Proper specimen preparation and handling are imperative.
• Avoid disturbances during testing to maintain accuracy.

flowchart TD
    A[Initiate Test] --> B[Prepare Specimen]
    B --> C[Use De-aerated Water]
    C --> D[Maintain Temperature 27±3°C]
    D --> E[Apply Pressure]
    E --> F[Measure Permeability]
    F --> G[Record Data & Observations]
    G --> H[Compile Report per Clause 9.1]
    H --> I[Conclude Test]

This outline ensures adherence to the prescribed test procedure under IS 4348.

Formulas and Considerations for Calculating Permeability Coefficient (IS 4348)

• Coefficient of Permeability (K):
  [ K = \frac{Q}{A \times T} \times \frac{L}{H} ] Where:

  • (K): permeability coefficient (cm/sec)
  • (Q): volume of water collected (ml)
  • (A): cross-sectional area of specimen (cm²)
  • (T): time during which (Q) was collected (sec)
  • (H/L): ratio of pressure head (H) to specimen thickness (L)

• Sample Representativeness: Samples should reflect the true average of the stone type or grade (Clause 2.1).

• Reporting: Include specimen ID, test duration, size, pressure, temperature, permeability at test and standard temperatures, and temporal permeability variation (Clause 9.1).

• Rounding: Apply IS 2-1960 standards for numerical rounding (Clause 0.3).

Parameter Summary Table

flowchart LR
    Q[Water Volume (ml)]
    A[Specimen Area (cm²)]
    T[Time (seconds)]
    HL[Pressure Head/Thickness]
    K[Permeability Coefficient (cm/sec)]

    Q --> K
    A --> K
    T --> K
    HL --> K

This calculation framework enables consistent permeability assessment in line with IS 4348.

Essential Contents of Permeability Test Reports as per IS 4348

According to Clause 9.1, reports must contain:

• Identification mark of the specimen
• Duration of the test
• Specimen dimensions
• Applied test pressure
• Test temperature
• Coefficient of permeability at the test temperature
• Temperature-corrected permeability coefficient (usually at 27°C)
• Observed trend in permeability over time (increase, decrease, rate)

Temperature Correction Formula Example

[ k_{27} = k_t \times \frac{\mu_t}{\mu_{27}} ]

Where:

• (k_t): measured permeability at test temperature (t)
• (k_{27}): permeability adjusted to 27°C
• (\mu_t), (\mu_{27}): dynamic viscosities of water at respective temperatures

Additional Notes:

• Use de-aerated water to prevent air bubble interference (Clause 4.2).
• Follow IS 2:1960 for rounding numerical data.
• Ensure specimen selection represents average stone quality (Clause 2.1).

flowchart TD
    A[Specimen Preparation] --> B[Perform Permeability Test]
    B --> C{Record Data}
    C --> D[Specimen ID]
    C --> E[Test Duration]
    C --> F[Specimen Dimensions]
    C --> G[Test Pressure & Temperature]
    C --> H[Calculate Permeability at Test Temp]
    H --> I[Correct Permeability to 27°C]
    I --> J[Evaluate Permeability Trend]
    J --> K[Generate Test Report]

This ensures comprehensive and standardized documentation as required by IS 4348.