soil-based blocks used in general building construction

IS 1725 - Scope: Key Specifications and Tables

Scope Summary:

• Covers soil-cement blocks with specified sizes and weathering test procedures.
• Focus on durability against weathering (rain impact and water exposure).

1. Block Sizes (Clause 4.1)

2. Weathering Test Procedure (Clause 4.1 & A-1)

• Test Setup:

  • Block mounted with one face exposed.
  • Water shower at 18 cm distance.
  • Shower simulates rain drop diameter: 2 mm (medium) to 4 mm (high).
  • Terminal velocity of raindrops: 6.5 m/s.
  • Rainfall intensity: 15-30 mm/hr.
  • Exposure duration: 2 hours.

• Acceptance Criteria:

  • Maximum pit diameter ≤ 1 cm.
  • Test on at least 3 blocks.

3. Units (SI Units)

4. Test Specimens (Clause 2.1)

• Select 3 whole blocks (A, B, C) after dimensional conformity test for weathering.

flowchart TD
    A[Select 3 Blocks] --> B[Mount block on test rig]
    B --> C[Expose one face to shower at 18 cm]
    C --> D[Simulate rain: 2-4 mm drops, 6.5 m/s velocity]
    D --> E[Expose for 2 hours]
    E --> F[Check pitting diameter ≤ 1 cm]
    F --> G{Pass/Fail}

Summary: IS 1725 defines soil-cement block sizes and a rigorous weathering

IS 1725: Classification and Specifications of Soil-Cement Blocks

1. Classification (Clause 3.1)

• Blocks are classified into:
  • Class 20 (20 MPa minimum compressive strength)
  • Class 35 (35 MPa minimum compressive strength)

2. Block Sizes (Clauses 4.1 & 4.2)

• Dimensions are measured for a sample of 20 blocks.
• Length, breadth, and height tolerances ensure uniformity.

3. Material & Manufacturing (Clause 2.1)

• Made from soil mixed with ordinary Portland cement or lime-pozzolana.
• Mixing preferably done mechanically.
• Blocks molded and cast as per specified sizes.

Summary Table: Block Classification and Sizes

flowchart LR
    A[Soil + Cement/Lime-Pozzolana] --> B[Mechanical Mixing]
    B --> C[Molding & Casting]
    C --> D[Blocks: Class 20 or Class 35]
    D --> E[Quality Check: Dimensions & Strength]

This classification ensures blocks meet strength and dimensional standards for structural use.

IS 1725: Sizes and Dimensions of Soil-Cement Blocks

Standard Sizes (Clause 4.1)

Dimensional Tolerances per 20 Blocks (Clause 4.2)

Note: Dimensions are total for 20 blocks (e.g., 19 cm × 20 = 380 mm nominal length).

Testing Procedure for Dimensions (Clause A-4.1)

• Blocks mounted on test rig with one face exposed to water shower.
• Shower distance: 18 cm.
• Exposure time: 2 hours.
• Check for pitting; max pit diameter ≤ 1 cm to pass.

Summary:

• 3 standard block sizes with specified dimensions.
• Dimensional tolerance ensures quality control.
• Weathering test ensures durability of exposed surfaces.

flowchart LR
    A[Block Size Selection]
    B[Dimension Check per 20 Blocks]
    C[Mount on Test Rig]
    D[Water Shower Exposure (2 hrs)]
    E[Inspect for Pitting ≤ 1 cm]
    F[Pass/Fail]

    A --> B --> C --> D --> E --> F

This ensures soil-cement blocks meet IS 1725 quality and dimensional standards.

IS 1725: Physical Requirements Summary

1. Frog Specification (Clause 4.3)

• Each block must have a frog on one flat side.
• Frog dimensions: 10 cm × 4 cm, depth 1 cm.

2. Dimensional Tolerances (Clause 4.2, Table 4)

3. Weathering Requirements (Clause 5.3 & Appendix A)

• Maximum weight loss after weathering test: ≤ 5%.
• Weathering test simulates:
  • Raindrop diameter: 2 mm (medium) to 4 mm (high intensity).
  • Terminal velocity: max 6.5 m/s.
  • Rainfall intensity: 15–30 mm/hr.

4. Sampling & Test Specimens (Clause 6.5)

• Weathering test parameters replicate natural rainfall impact conditions for durability assessment.

This ensures blocks meet dimensional accuracy and durability for structural use.

flowchart LR
    A[Block with Frog] --> B[Dimension Check]
    B --> C{Within Tolerance?}
    C -->|Yes| D[Proceed to Weathering Test]
    C -->|No| E[Reject Batch]
    D --> F[Weight Loss ≤ 5%?]
    F -->|Yes| G[Conforms to IS 1725]
    F -->|No| E

IS 1725: Sampling and Criteria for Conformity

Key Points from Clause 6 (Sampling & Conformity)

• Sampling and conformity criteria follow IS 5454-1978.
• Blocks are sampled after dimensional conformity tests.
• From the sample, 3 whole blocks (specimens A, B, C) are selected for further tests (Clause A-2.1).

Weathering Test (Clause 5.3 & Appendix A)

• Maximum weight loss after weathering test: ≤ 5%.
• Spray test (Clause 4.1):
  • Block face exposed to shower water at 18 cm distance for 2 hours.
  • Water must drain without wetting other faces.
  • Pitting diameter on surface must be ≤ 1 cm for passing.
  • Minimum 3 blocks tested.

Summary Table for Spray Test Setup

Sampling Procedure (IS 5454-1978)

• Follow standard sampling plan for lot acceptance.
• Test specimens selected randomly.
• Acceptance criteria based on sample test results per IS 5454.

flowchart TD
    A[Sample Blocks] --> B{Dimensional Conformity Test}
    B -->|Pass| C[Select 3 Blocks (A,B,C)]
    C --> D[Weathering Test (Weight loss ≤ 5%)]
    C --> E[Spray Test (Pit ≤ 1 cm)]
    D & E --> F{Conformity Criteria Met?}
    F -->|Yes| G[Accept Lot]
    F -->|No| H[Reject Lot]

References:

• IS 1725 Clause 6.1 & Appendix A
• IS 5454-1978 for sampling methodology

This ensures quality control of blocks by dimensional, weathering, and spray tests with clear acceptance criteria.

IS 1725 - Marking of Clay Building Bricks: Key Points

• Clause 7.1: Each brick block must be marked in the frog (the indentation on one face) with the manufacturer's identification mark or initials.

• Clause 7.1.1: Manufacturers may also use the ISI Certification Mark, which assures compliance with IS standards under ISI's inspection and quality control system.

Important Notes on ISI Mark:

• Governed by the Indian Standards Institution (Certification Marks) Act.
• Indicates production under continuous ISI supervision.
• License conditions for ISI mark use are provided by ISI.

Marking Summary Table:

Additional Reference:

• Marking ensures traceability and quality control.
• ISI mark is a legal certification symbol, not just a logo.

flowchart TD
    A[Brick Block] --> B[Frog]
    B --> C[Manufacturer's Mark/Initials]
    B --> D[ISI Certification Mark (Optional)]
    C --> E[Traceability]
    D --> F[Quality Assurance]

This concise marking protocol ensures bricks meet IS 1725 standards and maintain quality traceability.

IS 1725 Weathering Test Key Points

1. Principle (Clause 6.5)

• Rain drop diameter:
  • Medium intensity: ~2 mm
  • High intensity: ~4 mm
• Maximum terminal velocity: 6.5 m/s at impact
• Maximum rainfall intensity: 15-30 mm/hr

2. Test Specimens (Clause 5.3, A-2.1)

• Select 3 whole blocks (Specimens A, B, C) after dimensional conformity test.

3. Spray Test Procedure (Clause 4.1, Table A-4)

• Mount block exposing only one face to water spray.
• Shower nozzles placed 18 cm from block.
• Exposure duration: 2 hours.
• Water drains freely, no immersion.
• Examine surface for pitting:
  • Max pit diameter allowed: 1 cm.

4. Acceptance Criteria (Clause 5.3)

• Maximum weight loss ≤ 5% after weathering test.

Summary Table

flowchart TD
    A[Select 3 Blocks] --> B[Mount on Test Rig]
    B --> C[Expose One Face to Spray]
    C --> D[Spray Water @ 18 cm Distance]
    D --> E[2 Hours Exposure]
    E --> F[Check for Pitting (≤1 cm)]
    E --> G[Measure Weight Loss (≤5%)]
    F & G --> H{Pass/Fail}

This ensures durability of blocks against weathering as per IS 1725.