gypsum building plaster, Part 1: Excluding premixed lightweight plaster

IS 2547 Part 1: Scope - Key Specifications & Formulas

Scope:
Covers physical requirements and test methods for gypsum plasters.

Important Clauses & Formulas

• Rounding off test values:
  Final test values must be rounded per IS 2-1960, retaining significant figures as specified.

• Test result evaluation (Clause 6.4.1):
  For setting time, transverse strength, and residue on 1.18 mm sieve:
  [ \text{Calculate average } (X), \text{ range } (R) \ \text{Check } X - 0.4R \geq \text{min limit} \ \text{and } X + 0.4R \leq \text{max limit} ]

Table 2: Physical Requirements Summary

Notes

• *Transverse strength and mechanical resistance vary by plaster type (Plaster of Paris, Retarded Hemihydrate, Keene's plaster).
• Definitions as per IS 2469-1976 apply.

flowchart LR
    A[Test Samples] --> B[Calculate Average (X) & Range (R)]
    B --> C{Check Limits}
    C -->|X - 0.4R >= Min Limit| D[Pass Lower Bound]
    C -->|X + 0.4R <= Max Limit| E

IS 2547 Part 1 - Key Definitions & Specifications Summary

1. Definitions

• Refer to IS 2469-1976 for all gypsum plaster-related definitions (Clause 2.1).

2. Test Result Evaluation (Clause 6.4.1)

• Calculate average (X) and range (R) for setting time, transverse strength, residue on 1.18 mm sieve.
• Check compliance using:
  [ X - 0.4R \geq \text{Minimum limit}, \quad X + 0.4R \leq \text{Maximum limit} ]

3. Physical Requirements (Table 2, Clause 5.2)

4. Mechanical Resistance

• Indentation diameter limits for neat plaster vary by type (3–4.5 mm depending on plaster type).

5. Rounding Off

• Test results rounded per IS 2-1960 with significant digits matching specified values.

This concise summary captures key definitions, formulas, and physical requirements for gypsum plaster per IS 2547 Part 1. For detailed test methods, refer to IS 2542 (Part I)-1964.

Classification & Key Specifications as per IS 2547 Part 1

1. Classification Basis:

• Based on setting time, transverse strength, and residue on 1.18-mm IS sieve.
• Use average (X) and range (R) of test results.
• Calculate:
  [ X + 0.4R \quad \text{and} \quad X - 0.4R ]
• Compliance requires:
  [ X - 0.4R \geq \text{Minimum limit}, \quad X + 0.4R \leq \text{Maximum limit} ]

2. Rounding Off:

• Follow IS 2-1960 for rounding test results.
• Retain significant figures as per specified values.

3. Physical Requirements (Table 2 Highlights):

4. Mechanical Resistance:

• Diameter of indentation on set neat plaster:
  • Retarded hemi-hydrate: 3 - 4.5 mm
  • Keene's plaster: ≤ 3.5 mm

flowchart TD
    A[Test Results: Setting time, Strength, Residue] --> B[Calculate X and R]
    B --> C[Calculate X + 0.4R

IS 2547 Part 1: Chemical Requirements for Gypsum Plasters

Key Chemical Composition (Table 1)

Important Physical Requirements (Table 2)

IS 2547 Part 1: Physical Requirements for Gypsum Plaster (Clause 5.2, Table 2)

Important Notes (Clause 6.4.1):

• For setting time, transverse strength, and residue, calculate average (X) and range (R).
• Check:
  • ( X - 0.4R \geq ) minimum limit
  • ( X + 0.4R \leq ) maximum limit

Chemical Composition Summary (Clause 4.1, Table 1):

IS 2547 Part 1 — Sampling Key Points

Sampling Size (Clause 6.2, Table 3)

Sampling Procedure

• Random selection of packages from the lot is mandatory (Clause 6.2.1).
• Use procedures from IS 4905-1968 to ensure randomness.

Testing

• Samples are tested separately for each lot to verify conformity (Clause 6.1.1).
• Results are rounded off per IS 2-1960, maintaining the same significant figures as specified.

Summary Diagram

flowchart TD
    A[Lot of Packages] --> B[Determine Lot Size]
    B --> C{Lot Size}
    C -->|Up to 100| D[Select 3 Packages]
    C -->|101-150| E[Select 4 Packages]
    C -->|151-300| F[Select 5 Packages]
    C -->|301-500| G[Select 7 Packages]
    C -->|501+| H[Select 10 Packages]
    D & E & F & G & H --> I[Random Selection as per IS 4905-1968]
    I --> J[Test Samples Separately]
    J --> K[Round Results as per IS 2-1960]

This ensures statistically valid sampling and reliable test results for quality control.

IS 2547 Part 1 – Packaging and Marking Key Points

Packaging (Clause 7.1)

• Gypsum plaster must be dry, lump-free, and packed in watertight bags/containers.
• Markings on each package must include:
  • Manufacturer’s name
  • Class and type of plaster
  • Date of manufacture and batch number (if any)

Sampling for Testing (Clause 6.2 & Table 3)

Marking (Clause 7.2)

• Use of BIS Standard Mark is governed by the Bureau of Indian Standards Act, 1986.
• Manufacturers may apply for a license to use the Standard Mark.
• Marking with the Standard Mark is optional but recommended.

Summary Diagram: Packaging & Marking Process

flowchart TD
    A[Gypsum Plaster Production] --> B[Dry & Lump-Free]
    B --> C[Pack in Watertight Bags]
    C --> D[Mark Package with Info]
    D --> E[Sample Selection per Lot Size]
    E --> F[Test Composite Samples]
    F --> G{Test Results Satisfactory?}
    G -- Yes --> H[Mark with BIS Standard Mark (optional)]
    G -- No --> I[Reject Lot]

This ensures quality control and traceability in gypsum plaster packaging per IS 2547 Part 1.

IS 2547 Part 1: Criteria for Conformity (Clause 6.4)

A lot conforms if both 6.4.1 and 6.4.2 are satisfied:

1. Statistical Criteria (Clause 6.4.1)

• For setting time, transverse strength, residue on 1.18-mm IS sieve:
  • Calculate average ( X ) and range ( R ).
  • Compute: [ X - 0.4R \geq \text{Minimum limit} ] [ X + 0.4R \leq \text{Maximum limit} ]
  • Both must hold true for conformity.

2. Rounding Off (IS 2-1960)

• Final test values are rounded to the same decimal places as specified in the standard.

Key Physical Requirements (Table 2, Clause 5.2)

Summary Diagram

flowchart TD
    A[Start: Test a lot of gypsum plaster] --> B[Calculate average (X) and range (

IS 2547 Part 1: Determination of Soluble Sodium and Magnesium Salts

Key Specifications (Table 1 - Chemical Composition)

Procedure Summary (Clause A-1.1)

• Weigh 1 g of plaster (ground to pass 212 micron IS sieve).
• Add 100 ml water + 1 g salt-free gypsum in a polyethylene bottle.
• Shake occasionally for 1 hour to prevent caking.
• Allow to settle until clear supernatant liquid forms.
• Analyze supernatant for soluble Na and Mg salts.

Expression of Results

• Sodium salts expressed as Na2O %
• Magnesium salts expressed as MgO %

Chemical Requirements for Plaster Types (Excerpt from Table 1)

Notes:

• The method for quantifying soluble salts is detailed in Appendix A of IS 2547 Part 1.
• Loss on ignition and free lime tests are referenced in Appendices B and C respectively.

IS 2547 Part 1: Determination of Loss on Ignition (LOI)

Key Points and Specifications:

• Loss on Ignition (LOI) is the percentage mass loss when the sample is heated to a specified temperature, indicating moisture, volatile matter, and carbonates.

• Limits for LOI (% by mass) from Table 1 (Clause 4.1):

• Test Method Reference: See Appendix B of IS 2547 Part 1 for detailed procedure.

Calculation of Average and Range (Clause 6.4.1):

For test results (including LOI), calculate:

• Average, ( X = \frac{\sum x_i}{n} )
• Range, ( R = \max(x_i) - \min(x_i) )

Then verify:

[ X - 0.4R \geq \text{Minimum Limit} ] [ X + 0.4R \leq \text{Maximum Limit} ]

Additional Chemical Limits (Table 1):

• Soluble magnesium salts (as MgO): Max 0.3%
• Soluble sodium salts (as Na2O): Max 0.3%

Summary:

• LOI indicates impurities and moisture.
• Must be within specified limits for quality assurance.
• Use average and range method for test validation.
• Refer to Appendix B for detailed LOI test procedure.

flowchart LR
    A[Sample Preparation] --> B[Weigh Sample]
    B --> C[Heat to Specified Temp]
    C --> D[Cool and Weigh Residue]
    D --> E[Calculate LOI = ((Initial - Final)/Initial)*100]
    E --> F{Check Limits}
    F -->|Within Limits| G[Accept Sample]
    F -->|Out of Limits| H[Reject Sample]

This ensures compliance with IS 2547 Part 1 for plaster quality control.

IS 2547 Part 1: Determination of Free Lime in Gypsum Plaster

Key Specification:

• Free lime minimum content:
  • Retarded Hemihydrate Gypsum Plaster: ≥ 3% (Clause 4.1, Table 1)

Chemical Composition Table Extract (Table 1):

Method for Free Lime Determination (Appendix C):

• Use 5 g sample.
• Titrate with 0.5 N HCl;
• 1 ml 0.5 N HCl = 0.37% Ca(OH)2 free lime.

Calculation Formula:

[ \text{Free Lime %} = \frac{\text{ml HCl used} \times 0.37}{\text{sample weight in grams}} \times 100 ]

Summary of Test Procedure:

1. Weigh 5 g of plaster sample.
2. Titrate with 0.5 N HCl.
3. Calculate free lime % using above formula.
4. Ensure free lime ≥ 3% for Retarded Hemihydrate Gypsum Plaster.

This ensures gypsum plaster quality per IS 2547 Part 1 for durability and performance.