concrete masonry units, Part 2: Hollow and solid lightweight concrete blocks

IS 2185 Part 2 — Scope & Measurement of Dimensions

Scope (Clause 2.0)

• Defines terms relevant to concrete masonry units.
• Applies to precast concrete blocks for masonry construction.

Measurement of Dimensions (Clause 8.2 & Appendix A)

• Overall dimensions of concrete blocks must conform to specified sizes with tolerances.
• Measurement tools:
  • Steel scale: Graduated in 1 mm divisions for overall size.
  • Caliper rule: Graduated in 0.5 mm divisions for face shell and web thickness, with jaws 15–25 mm long.

Key Points:

Tolerances

• Refer to Clause 3 and Appendix A for permissible dimensional tolerances.

flowchart LR
    A[Concrete Block] --> B[Measure Overall Dimensions]
    B --> C[Steel Scale (1 mm)]
    A --> D[Measure Face Shell & Web Thickness]
    D --> E[Caliper Rule (0.5 mm, jaws 15-25 mm)]

This ensures uniformity and quality control in block manufacturing per IS 2185 Part 2.

IS 2185 Part 2 — Definitions & Key Specifications

1. Definitions (Clause 2.0)

• Defines terms related to concrete masonry units (CMUs) such as load-bearing, non-load-bearing, hollow, and solid units.
• Ensures uniform understanding for design and testing.

2. Physical Requirements (Clause 5.8 & Table 1)

• Water absorption is average of 3 units tested as per Appendix D.
• Strength values are minimum compressive strengths after curing.

3. Dimensions (Clause 8.2 & Appendix A)

• Overall unit dimensions measured as per Appendix A.
• Must comply with nominal sizes in Clause 3 with specified tolerances.
• Ensures interchangeability and proper fit in masonry.

Summary:

• Use Table 1 for selecting block grade based on strength & absorption.
• Confirm dimensions per Appendix A and Clause 3.
• Water absorption and compressive strength are critical for durability and load capacity.

flowchart TD
    A[Definitions - Clause 2.0] --> B[Physical Requirements - Clause 5.8]
    B --> C[Min Compressive Strength & Water Absorption]
    A --> D[Dimensions - Clause 8.2]
    D --> E[

IS 2185 Part 2: Shapes and Sizes of Concrete Masonry Units

Key Specifications (Clause 3.1 & 3.2.1)

Concrete masonry units (CMUs) include various shapes:

• Stretcher, Corner, Double Corner (Pier)
• Jamb, Header, Bull Nose, Partition block
• Concrete floor units

Nominal Dimensions (Clause 3.2.1)

• Units can be customized by agreement (Clause 3.2.2).
• Special blocks like jallie or ornamental blocks may not follow these sizes.

Compressive Strength (Clause 5.1)

[ f_c = \frac{P_{max}}{A_g} ]

• (f_c): compressive strength (N/mm²)
• (P_{max}): maximum load (N)
• (A_g): gross cross-sectional area (mm²), including cells and re-entrant spaces unless occupied by adjacent masonry.

Summary Diagram of Typical CMU Dimensions

graph TD
    A[Concrete Masonry Unit] --> B[Length: 400/500/600 mm]
    A --> C[Height: 100/200 mm]
    A --> D[Width: 50/75/100/150/200/250/300 mm]

Use these sizes for design and procurement, ensuring compatibility with structural and architectural requirements.

IS 2185 Part 2: Key Material Specifications

1. Physical Requirements (Clause 5.8, Table 1)

2. Testing Methods

• Compressive Strength (Clause 8.4): Average of 8 units; individual unit min strength per Table 1, tested as per Appendix C.
• Water Absorption (Clause 5.8): Average of 3 units, tested as per Appendix D.

3. Additional Specifications

• Average dimensions and thicknesses (face-shell, web) must be reported for 20 specimens (Clause 3.3).
• Sulphur content in proprietary mixtures: 40-60% by mass (Clause 3.1).

Summary Formula for Compressive Strength:

[ f_c = \frac{\sum_{i=1}^8 f_i}{8} \geq f_{min} ]

where ( f_i ) = compressive strength of each unit, ( f_{min} ) = minimum average strength from Table 1.

This ensures durability and structural adequacy of masonry units per IS 2185 Part 2.

IS 2185 Part 2: Mixing and Manufacture of Concrete Blocks

Key Specifications:

• Clause 6.2: Concrete shall normally be mixed in a mechanical mixer for uniformity.
• Clause 6.2.1: Mixing continues until the mass is uniform in colour and consistency.
• Clause 6.2.2: Hand mixing (if permitted) must be done on a water-tight platform until uniformity is achieved.

Important Notes:

• Mixing time depends on mixer type but typically ranges 2-5 minutes for mechanical mixers.
• Hand mixing requires thorough turning and blending to avoid non-uniformity.
• Use of oil on capping plates is optional if separation without damage is possible.

Typical Mixing Procedure:

Sulphur Content (Clause 3.1):

• Sulphur content in mixtures: 40-60% by mass in proprietary or lab-prepared mixes.

flowchart LR
    A[Start: Dry Ingredients] --> B[Mechanical Mixing]
    B --> C{Uniform Colour & Consistency?}
    C -- No --> B
    C -- Yes --> D[Add Water]
    D --> E[Mix until Uniform]
    E --> F[Ready for Moulding]

This ensures consistent quality and strength of concrete blocks as per IS 2185 Part 2.

IS 2185 Part 2: Placing and Compaction of Concrete Blocks

Key Specifications (Clause 6.3 & 6.3.1)

• Layer Thickness: Place concrete mix in layers of 50 to 75 mm.
• Compaction: Each layer must be thoroughly tamped using suitable tampers.
• Finishing: After filling, strike off the top level with a trowel for a smooth finish.

Compressive Strength (Clause 8.4 & Appendix C)

• Strength is determined by testing 8 units; average and individual minimum values must meet Table 1 requirements.
• Testing method: As per Appendix C, compressive strength is measured on blocks after curing.

Typical Placing & Compaction Procedure

flowchart TD
    A[Start: Prepare mould] --> B[Place concrete mix in 50-75 mm layers]
    B --> C[Tamp each layer thoroughly]
    C --> D[Fill mould completely]
    D --> E[Strike off surface level with trowel]
    E --> F[Cure blocks as per standards]
    F --> G[Test compressive strength]

Summary Table (Example from Table 1 - Compressive Strength)

(Refer IS 2185 Part 2 Table 1 for exact values)

Note: Proper compaction ensures uniform density and strength; inadequate tamping leads to weak blocks.

IS 2185 Part 2: Appearance and Surface Finish - Key Specifications

Measurement of Dimensions (Clause 8.2 & Appendix A)

• Overall dimensions measured with a steel scale (1 mm divisions).
• Face shell and web thickness measured with a caliper rule (0.5 mm divisions, jaw length 15-25 mm).
• Measurements must be accurate to ±0.0025 mm immediately after specimen removal from water (Clause 4.1).
• Length measurement is relative to an Invar rod of similar length to minimize thermal expansion errors.

Tolerances (Clause 8.2)

• Dimensions must comply with specified tolerances in Clause 3 (refer to IS 2185 Part 2 Table for exact values).
• Surface finish should be free from visible defects like cracks, honeycombing, or excessive roughness.

Summary Table for Measurement Tools

flowchart LR
    A[Specimen Removal from Water] --> B[Wipe Grease from Steel Balls]
    B --> C[Measure Length]
    C --> D[Compare with Invar Rod]
    D --> E[Record Original Wet Measurement]

This ensures precise dimensional accuracy and surface quality compliance per IS 2185 Part 2.

IS 2185 Part 2: Physical Requirements Summary

1. Water Absorption (Clause 5.8)

• Average of 3 units tested per Appendix D.
• Max average water absorption depends on concrete density:
  • For concrete density < 1360 kg/m³: Use column (4)
  • For concrete density < 1600 kg/m³: Use column (5)

2. Minimum Compressive Strength (Clause 8.4)

• Average of 8 units and individual unit minimum strength tested per Appendix C.
• Values from Table 1:

3. Dimensions (Clause 8.2)

• Measured as per Appendix A.
• Must conform to specified tolerances in Clause 3.

Key Notes:

• Water Absorption affects durability.
• Compressive Strength ensures structural performance.
• Dimension tolerances maintain uniformity and fit.

flowchart LR
    A[Physical Requirements] --> B[Water Absorption]
    A --> C[Compressive Strength]
    A --> D[Dimensions]
    B --> E{Concrete Density}
    E -->|<1360 kg/m³| F[Use Table 1 Col 4]
    E -->|<1600 kg/m³| G[Use Table 1 Col 5]

IS 2185 Part 2: Key Testing Methods & Specifications

1. Compressive Strength Test (Appendix C, Clause 8.4)

• Loading Rate:

  • Apply load up to 50% of expected max load at any convenient rate.
  • Then apply remaining load uniformly over 1 to 2 minutes at a controlled head travel rate.

• Purpose: Ensures consistent and accurate strength measurement.

2. Drying Shrinkage Test (Appendix E, Clause 8.6)

• Number of Tests:

  • Minimum 20 full-size units for length, width, height measurements.
  • For cored units, also measure minimum thickness of face shells and webs.

• Measurements:

  • Length, width, height recorded at intervals to calculate shrinkage.

Key Formula for Compressive Strength, ( f_c ):

[ f_c = \frac{P}{A} ]

• (P) = Maximum load at failure (N)
• (A) = Cross-sectional area (mm²)

Summary Table: Test Specimens & Parameters

flowchart TD
    A[Start Test] --> B[Apply Load up to 50%]
    B --> C[Control Load for 1-2 min]
    C --> D[Record Max Load]
    D --> E[Calculate Compressive Strength]

This ensures compliance with IS 2185 Part 2 testing protocols for reliable structural performance evaluation.

IS 2185 Part 2: Sampling of Concrete Blocks

Key Clauses on Sampling:

• Clause 10.2: Sampling in Motion

  • Samples should be taken during block movement (loading/unloading).
  • Divide the batch into convenient portions.
  • Draw one sample from each portion to meet the minimum sample size (Clause 10.1).

• Clause 10.3: Sampling from a Stack

  • Samples must be taken randomly from:
    • Top of stacks
    • Accessible sides
    • Interior by opening trenches from the top

• Clause 9.1: Testing Samples

  • Tests (Appendices A-F) must be conducted on these samples.
  • Samples ensure conformity with physical requirements in Clause 8.

Sampling Specifications Summary:

Sampling Procedure Flow:

flowchart TD
    A[Batch of Blocks] --> B{Divide into Portions}
    B --> C[Draw 1 Sample per Portion]
    C --> D[Minimum Sample Size Met?]
    D -- No --> B
    D -- Yes --> E[Conduct Tests (Appendices A-F)]
    E --> F[Verify Conformity with Clause 8]

Note:

• Sampling ensures representativeness and reliability of test results.
• Follow random selection to avoid bias.
• Refer Appendix A for dimensional measurement methods.

IS 2185 Part 2: Criteria for Conformity

Key Clauses Summary:

• Clause 11.1: Lot conformity depends on fulfilling conditions in Clauses 11.2 to 11.5.
• Clause 8.2 & Appendix A: Dimensional measurements are per Appendix A.
• Clause 8.4 & Table 1: Compressive strength requirements.
• Clause 9.1: Tests (Appendices A-F) on samples per sampling procedure (Clause 10).

Important Specifications:

Compressive Strength (Table 1 excerpt):

Conformity Criteria Flow:

flowchart TD
    A[Start: Sample Lot] --> B{Dimensional Check (Appendix A)}
    B -- Pass --> C{Compressive Strength Test (Table 1)}
    B -- Fail --> F[Lot Rejected]
    C -- Pass --> D{Other Tests (Appendices B-F)}
    C -- Fail --> F
    D -- Pass --> E[Lot Accepted]
    D -- Fail --> F

Summary:
To confirm conformity, verify dimensional accuracy, conduct compressive strength tests ensuring average and individual units meet minimum values, and perform other specified tests on sampled units as per the standard.

IS 2185 Part 2: Manufacturer's Certificate Key Points

• Clause 12.1: The manufacturer must ensure masonry units conform to IS 2185 Part 2 requirements and provide a Manufacturer's Certificate upon request.

• Certificate should confirm:

  • Compliance with compressive strength as per Clause 8.4 and Table 1 (average of 8 units).
  • Water absorption limits per Clause 11.6 (mean ≤ max limit in Clause 8.5).
  • Dimensional tolerances and measurements as per Clause 2.1 and Appendix A (20 full-size units measured).

Key Table Reference (Excerpt from Table 1: Compressive Strength for Masonry Units)

Typical Manufacturer's Certificate Format

flowchart TD
    A[Manufacturing] --> B[Quality Checks]
    B --> C{Tests}
    C -->|Compressive Strength| D[Appendix C Test]
    C -->|Water Absorption| E[Clause 11.6]
    C -->|Dimensions| F[Clause 2.1]
    D & E & F --> G[Manufacturer's Certificate]
    G --> H[Provided to Purchaser]

This ensures traceability and compliance for masonry units per IS 2185 Part 2.

IS 2185 Part 2: Independent Tests Key Points

1. Number of Tests (Clause 10.4 & E-1)

• Minimum number of specimens for independent tests should be as per Clause 10.4 and Appendix E (E-1).
• Typically, 3 specimens per test age are recommended for reliable results.

2. Compressive Strength Test (Appendix C, Clauses 8.4 & 9.1)

• Speed of Testing (C-4.2):

  • Load applied up to 50% of expected max load at any convenient rate.
  • Remaining load applied uniformly over 1 to 2 minutes at a constant rate of moving head travel.

• Calculation: [ f_c = \frac{P}{A} ] Where:

  • ( f_c ) = compressive strength (N/mm²)
  • ( P ) = maximum load applied (N)
  • ( A ) = cross-sectional area of specimen (mm²)

3. Drying Shrinkage Test (Appendix E, Clauses 8.6 & 9.1)

• Number of specimens: Minimum 3 specimens per test.
• Measurements taken at specified intervals to monitor shrinkage strain.

Summary Table: Test Specimens & Rate

flowchart TD
    A[Start Test] --> B{Load up to 50% max?}
    B -- Yes --> C[Apply load at any rate]
    B -- No --> D[Control machine for uniform load]
    D --> E[Apply load over 1-2 minutes]
    E --> F[Record max load]
    F --> G[Calculate compressive strength]

This ensures standardized, reliable independent testing as per IS 2185 Part 2.

IS 2185 Part 2 — Marking of Concrete Masonry Units

Key Specifications (Clause 14.1 & 14.1.1)

• Permanent marking on each unit must include:
  • Manufacturer's identification
  • Grade of the unit
  • Year of manufacture (if requested by purchaser)
• Optional marking:
  • ISI Certification Mark (subject to ISI rules and licensing)

Measurement of Dimensions (Clause 8.2 & Appendix A)

• Overall dimensions: Measured with a steel scale graduated in 1 mm divisions.
• Face shell and web thickness: Measured with a caliper rule graduated in 0.5 mm divisions.
• Caliper jaws length: 15 mm to 25 mm (parallel jaws).

Summary Table

flowchart TD
    A[Concrete Masonry Unit] --> B[Marking]
    B --> C[Manufacturer ID]
    B --> D[Grade of Unit]
    B --> E[Year of Manufacture (optional)]
    B --> F[ISI Certification Mark (optional)]
    A --> G[Dimension Measurement]
    G --> H[Overall Dimensions (1 mm scale)]
    G --> I[Face Shell & Web Thickness (0.5 mm caliper)]

This ensures traceability, quality assurance, and compliance with IS 2185 Part 2.