burnt clay hollow bricks for walls and partitions - Specification

IS 3952: Scope - Key Specifications & Tables

Scope Summary:

• Applies to shell and web thickness, dimensional tolerances, and test methods for bricks (clay or similar).
• Definitions per IS 2248-1981.
• Rounding off test results per IS 2-1960.

Key Specifications

Dimensional Tolerances for 20 Bricks (mm)

Testing Methods (Figures referenced)

• Fig. 1: Test for winding or bowing in length.
• Fig. 2: Test for concavity or convexity.
• Fig. 3: Test for edge correctness using builder’s square.

Notes

• Final test values must be rounded as per IS 2-1960.
• All dimensional tolerances apply to overall measurements of 20 bricks, ensuring consistency in production quality.

flowchart TD
    A[Brick Dimensions] --> B[Thickness Checks]
    B --> C{Shell >= 11mm?}
    B --> D{Web >= 8mm?}
    A --> E[Dimensional Tolerances for 20 Bricks]
    E --> F[Length 290mm: 5680-5920mm]
    E --> G[Width 190mm: 3720-3880mm]
    E --> H[Height 140mm: 2740-2860mm]
    E --> I[Height 90mm: 1760-1840mm]
    A --> J[Tests]
    J --> K[Winding/Bowing]
    J --> L[Concavity/Convexity]
    J --> M[Edge Correctness]

This summary ensures compliance with IS 3952 scope requirements for brick dimensions and quality control.

IS 3952 - Definitions & Key Specifications

1. Definitions (Clause 2.1):

• Refer to IS 2248:1981 for all terms and definitions related to burnt clay building bricks.

2. Water Absorption (Clause 3.3):

• Average water absorption is calculated from 6 specimens.
• Formula:
  [ \text{Water Absorption} = \frac{\sum_{i=1}^6 \text{Absorption}_i}{6} ]

3. Dimensional Tolerances (Clause 5.3):
Permissible tolerances on overall dimensions for 20 bricks (in mm):

4. Rounding Off (Clause 0.4):

• Final test values shall be rounded as per IS 2:1960, matching the significant figures of the specified values.

This ensures compliance with IS 3952 for brick quality control, dimensional accuracy, and test reporting.

IS 3952: General Requirements Summary

1. Thickness Minimums (Clause 5.1.1)

• Shell thickness: ≥ 11 mm
• Web thickness: ≥ 8 mm

2. Dimensional Tolerances (Clause 5.3)

Permissible tolerances on overall dimensions (for 20 bricks):

3. Testing for Geometrical Accuracy

• Winding or Bowing: Checked along length dimension (see Fig. 1)
• Concavity or Convexity: Checked on webs (see Fig. 2)
• Edge correctness: Verified using builder’s square (see Fig. 3)

4. Rounding Off (Clause 0.4)

• Follow IS 2:1960 for rounding test results.
• Retain the same number of significant digits as specified values.

flowchart TD
    A[Brick Shell] -->|Thickness ≥ 11mm| B[Thickness Check]
    A -->|Web Thickness ≥ 8mm| C[Web Thickness Check]
    D[Dimensional Tolerance] --> E[Measure 20 Bricks]
    E --> F{Check Min & Max Limits}
    G[Geometrical Tests] --> H[Winding/Bowing Test]
    G --> I[Concavity/Convexity Test]
    G --> J[Edge Correctness Test]

This concise summary covers key general requirements from IS 3952 for shell and web thickness, dimensional tolerances, and testing methods.

IS 3952: Types of Bricks & Key Specifications

Types of Bricks (Clause 4.1)

• Type A: Both faces keyed for plastering/rendering.
• Type B: Both faces smooth, suitable for use without plastering.
• Type C: One face keyed, one face smooth.

Dimensions of Burnt Clay Hollow Bricks (Clause 5.1)

Permissible Tolerances on Overall Measurements of 20 Bricks (Clause 5.3)

Modular Size Limits for Individual Bricks (Clause 5.3.2)

Additional Notes:

• Crushing Strength (Clause 6) is critical for structural use but specific values/formulas are in IS 3495 or IS 1077.
• Keying improves plaster adhesion; smooth faces are for exposed brickwork.

flowchart LR
    A[Types of Bricks] --> B[Type A: Both faces keyed]
    A --> C[Type B: Both faces smooth]
    A --> D[Type C: One face keyed, one smooth]
    
    E[Dimensions] --> F[Length: 190, 290 mm]
    E --> G[Width: 90, 140, 190 mm]
    E --> H[Height: 90 mm]
    
    I[Tolerances] --> J[Overall measurements for 20 bricks]
    I --> K[

IS 3952: Dimensions and Tolerances for Bricks

Key Specifications:

• Minimum thickness:

  • Shell: ≥ 11 mm
  • Web: ≥ 8 mm

• Tolerance on overall dimensions (for 20 bricks):

• Angle tolerance:
  • Max deviation from 90° such that when a builder's steel square is placed, the gap ≤ 5 mm.

Tests for Tolerances:

• Winding/Bowing (Length)
• Concavity/Convexity (Web thickness ≥ 8 mm)
• Correctness of Edges (using builder's square)

Summary Table for Thickness and Angle Tolerance:

flowchart LR
    A[Brick Dimensions] --> B[Measure 20 bricks]
    B --> C{Check dimension tolerances}
    C -->|Within Min-Max| D[Accept]
    C -->|Outside limits| E[Reject]
    A --> F[Check thickness]
    F -->|Shell ≥11mm & Web ≥8mm| D
    F -->|Less thickness| E
    A --> G[Check angles with builder's square]
    G -->|Gap ≤ 5mm| D
    G -->|Gap > 5mm| E

This ensures bricks meet dimensional accuracy and quality for construction.

IS 3952: Crushing Strength of Bricks

Key Specifications:

• Mortar strength: 28 to 42 N/mm² before testing (Clause 3.1)
• Load application rate: 14 N/mm² per minute until failure (≥140 kgf/cm²/min) (Clause 3.1)
• Specimen setup: Bricks crushed between 3-ply plywood sheets (~3 mm thick) (Clause 3.1)

Crushing Strength Calculation (Clause A-4.1):

[ \text{Crushing Strength (N/mm}^2) = \frac{\text{Maximum Load (N)}}{\text{Area of Brick Face (mm}^2)} ]

• Use the average crushing strength of 6 bricks as the batch strength.
• Area = face area of the brick subjected to load (usually the smallest cross-sectional area).

Brick Dimensions (Clause 5.3.2):

Summary:

• Crush bricks axially at uniform load rate.
• Calculate crushing strength as load/area.
• Average results over 6 bricks.
• Brick sizes should not exceed modular sizes.

flowchart TD
    A[Prepare Brick Specimen] --> B[Apply Load Axially]
    B --> C{Load Reaches Failure}
    C --> D[Record Maximum Load]
    D --> E[Calculate Crushing Strength = Load / Area]
    E --> F[Average Strength of 6 Bricks]
    F --> G[Determine Batch Quality]

This ensures consistent and reliable crushing strength evaluation per IS 3952.

IS 3952 - Water Absorption Test for Bricks

Key Specifications & Procedure:

• Drying: Specimens dried at 110-115°C to constant mass (typically 48 hrs).
• Cooling: Cool to room temp (~4 hrs naturally, 2 hrs with fan).
• Soaking: Immerse fully in clean water at 27 ± 2°C for 24 hours.
• Weighing: Wipe surface water, weigh within 3 minutes.

Formula for Water Absorption (% by mass):

[ \text{Water Absorption} = \frac{M_2 - M_1}{M_1} \times 100 ]

Where:

• (M_1) = Mass of dry specimen (g)
• (M_2) = Mass after soaking (g)

Averaging:

• Test 6 specimens.
• Average their water absorption values for the lot.

Summary Table:

flowchart TD
    A[Dry Specimen] -->|Dry at 110-115°C| B[Constant Mass]
    B -->|Cool to room temp| C[Weigh dry mass M1]
    C -->|Soak in water 27±2°C for 24 hrs| D[Weigh wet mass M2]
    D -->|Calculate Water Absorption| E[Water Absorption %]

This ensures bricks meet durability and quality standards as per IS 3952.

IS 3952 - Efflorescence: Key Points & Test Method

Efflorescence Overview (Clause 8)

• Efflorescence is the deposit of soluble salts on brick surfaces, affecting aesthetics and durability.
• IS 3952 references a specific test method for efflorescence (Part 3 - second revision), but detailed procedures are not fully described in the provided text.

Related Specifications:

• Water Absorption (Clause 7.1): Max 20% by mass, tested per Appendix B.
• Proper drying and weighing of bricks before testing (Clause B-3.1).
• Bricks must be dried to constant mass at 110-115°C, cooled to room temperature before testing.

Efflorescence Test (Summary from IS 3952 & common practice):

• Bricks are partially immersed in water for a specified time.
• After drying, the surface is visually inspected for white salt deposits.
• Efflorescence is classified qualitatively (Nil, Slight, Moderate, Heavy).

Typical Efflorescence Rating Table (Example):

Additional Notes:

• Efflorescence depends on soluble salts, water absorption, and curing.
• Controlling water absorption (<20%) helps reduce efflorescence risk.
• Standard Mark (Clause 10.1.1) ensures quality compliance.

flowchart LR
    A[Brick Sample] --> B[Dry to constant mass at 110-115°C]
    B --> C[Cool to room temperature]
    C --> D[Partial immersion in water at 27±2°C for 24 hrs]
    D --> E[Dry and inspect surface]
    E --> F{Efflorescence Rating}
    F -->|Nil| G[No deposit]
    F -->|Slight| H[Up to 10% coverage]
    F -->|Moderate| I[10-50% coverage]
    F -->|Heavy| J

IS 3952: Sampling Key Points

Sampling Procedure (Clause 9.1)

• For every 1,000 bricks or fraction thereof in a lot, select at least 6 bricks at random.
• Minimum number of bricks for testing per lot: 20 bricks.
• All sampled bricks are checked for requirements in Clauses 3, 4, and 5.

Water Absorption (Clause 3.3)

• Average water absorption is calculated from the 6 specimens sampled.

Rounding Off (Clause 0.4)

• Final values from tests should be rounded as per IS 2:1960, keeping the same significant digits as specified.

Brick Dimensions (Clause 5.3.2)

Summary Formula

• Number of bricks sampled (n) = max(6 × number_of_thousands_in_lot, 20)

flowchart TD
    A[Start: Brick Lot] --> B{Count bricks in lot}
    B -->|<1000| C[Sample 6 bricks]
    B -->|≥1000| D[Sample 6 bricks per 1000 bricks]
    C --> E[Minimum 20 bricks per lot]
    D --> E
    E --> F[Conduct tests for clauses 3,4,5]
    F --> G[Calculate average water absorption]
    G --> H[Round off results per IS 2:1960]
    H --> I[Evaluate compliance]

This ensures representative sampling and consistent test data for quality control.

IS 3952 - Marking of Burnt Clay Building Bricks

Key Specifications (Clause 10.1 & 10.1.1)

• Manufacturer's Identification:
  Each brick must be marked with the manufacturer's identification mark or initials for traceability.

• Standard Mark:
  Bricks may bear the BIS Standard Mark indicating compliance with IS 3952 under BIS supervision.

  • Use governed by the Bureau of Indian Standards Act, 1986.
  • Indicates quality assurance via inspection, testing, and continuous surveillance by BIS.

Rounding Off Results (Clause 0.4)

• Test results must be rounded off as per IS 2:1960.
• The number of significant digits in the rounded value must match the specified value in the standard.

Summary Table: Marking Requirements

Notes:

• Marking ensures quality traceability and consumer confidence.
• For licensing and use of the Standard Mark, contact BIS.

flowchart LR
    A[Brick] --> B{Marking}
    B --> C[Manufacturer's ID Mark]
    B --> D[Optional BIS Standard Mark]
    D --> E[Quality Assurance by BIS]

This ensures bricks comply with IS 3952 and maintain quality standards.

IS 3952: Method of Test for Determination of Crushing Strength

Test Procedure (Clause 3.1)

• Test mortar strength between 28 to 42 N/mm².
• Crush specimen between 3-ply plywood sheets (≈3 mm thick).
• Apply axial load at a uniform rate of 14 N/mm² per minute until failure.

Calculation of Crushing Strength (Clause 4.1)

[ \text{Crushing Strength} = \frac{P_{\max}}{A} ]

• (P_{\max}) = Maximum load at failure (N)
• (A) = Cross-sectional area of the brick (mm²)
• Average crushing strength = Arithmetic mean of 6 bricks tested.

Brick Dimensions (Clause 5.3.2, Table 5)

Minimum Average Crushing Strength (Clause 6.1)

• As per IS 3952, minimum average crushing strength depends on brick type (refer to IS 1077 for typical values, usually ≥ 35 N/mm² for common burnt clay bricks).

flowchart TD
    A[Prepare Specimen] --> B[Check Mortar Strength (28-42 N/mm²)]
    B --> C[Place Brick Between Plywood Sheets]
    C --> D[Apply Axial Load @ 14 N/mm²/min]
    D --> E[Record Max Load at Failure]
    E --> F[Calculate Crushing Strength = Max Load / Area]
    F --> G[Average Crushing Strength of 6 Bricks]

Summary: Crush bricks between plywood sheets at a steady load rate, calculate strength using max load divided by area, and average results over 6 samples. Use modular sizes to verify brick dimensions.

IS 3952: Water Absorption Test for Bricks

Test Procedure (Clauses 3.1 to 3.3)

• Drying:
  Dry specimen in a ventilated oven at 110-115°C until constant mass (usually 48 hrs). Cool to room temperature (4 hrs naturally or 2 hrs with fan).

• Soaking:
  Immerse dry specimen completely in clean water at 27 ± 2°C for 24 hours.

• Weighing:
  After soaking, wipe surface water with a damp cloth and weigh immediately (within 3 minutes).

Formula for Water Absorption (% by mass)

[ \text{Water Absorption} = \frac{M_2 - M_1}{M_1} \times 100 ]

Where:

• ( M_1 ) = Mass of dry specimen (g)
• ( M_2 ) = Mass after soaking (g)

Final Value

• Average water absorption of six specimens is reported as the lot's water absorption.

Summary Table

This test ensures brick quality by measuring porosity and durability via water absorption.