Concrete masonry units, Part 1: Hollow and solid concrete blocks

Scope & Key Specifications from IS 2185 (Part 1):

• Scope: Covers concrete masonry units (blocks) used for load-bearing and non-load-bearing walls.
• Measurement (Clause 1.1 & 9.2):
  • Overall dimensions measured with steel scale (±1 mm).
  • Face shell & web thickness with caliper (±0.5 mm).
  • Sample size: 20 full-size units for dimensional checks.
• Physical Requirements (Clause 5.2, Table 2):

• Testing: Samples tested per Annex B to G for physical conformity.
• Sampling: Per Clause 11 for quality assurance.

Summary Diagram of Measurement Process

flowchart TD
    A[Select 20 Units] --> B[Measure Length, Width, Height (±1 mm)]
    B --> C[Measure Face Shell & Web Thickness (±0.5 mm)]
    C --> D[Test Physical Properties (Compressive Strength)]
    D --> E{Conform to IS 2185?}
    E -- Yes --> F[Approve Batch]
    E -- No --> G[Reject/Retest Batch]

This ensures standardized quality and dimensions for concrete masonry units as per IS 2185 Part 1.

IS 2185 (Part 1) - Key Definitions & Specifications

1. Definitions (Clause 3.0)

• The standard defines types and grades of concrete masonry units (CMUs) based on load-bearing capacity, density, and strength.
• Units are classified as Hollow (open/closed cavity) or Solid load bearing units.
• Grades are designated as A, B, or C with numeric values indicating minimum compressive strength in N/mm².

2. Physical Requirements (Table 2, Clause 5.2)

3. Measurement Specifications (Clause 1.1)

• Overall dimensions: Measured with steel scale (1 mm divisions).
• Face shell & web thickness: Measured with caliper (0.5 mm divisions, jaws 15-25 mm).
• Sample size: 20 full-size units for length, width, height, and thickness.

Summary Diagram of Unit Classification

graph TD
    A[Concrete Masonry Units]
    A --> B[Hollow Units]
    A --> C[Solid Units]
    B --> B1[Grade A (≥1500 kg/m³)]
    B --> B2[Grade B (1100-1500 kg/m³)]
    C --> C1[Grade C (≥1800 kg/m³)]
``

IS 2185 Part 1: Dimensions and Tolerances for Concrete Blocks

Key Definitions (Clause 3.12)

• Width: External dimension at bedding plane, measured perpendicular to length and height.

Measurement Procedure (Annex B)

• Use a steel scale with 1 mm divisions for length, width, height.
• Use a caliper with 0.5 mm divisions and jaws 15-25 mm long for face shell and web thickness.
• Measure 20 full-size units for length, width, height.
• For cored units, also measure minimum thickness of face shells and webs.

Tolerances (Clause 4 and 9.2)

• Overall dimensions must conform to tolerances specified in Clause 4 (not detailed here).
• Measurements as per Annex B ensure compliance.

Typical Tolerance Table (Summary from IS 2185 Part 1)

Measurement Setup Diagram

graph TD
A[Concrete Block] --> B[Length (Steel Scale)]
A --> C[Width (Steel Scale)]
A --> D[Height (Steel Scale)]
A --> E[Face Shell Thickness (Caliper)]
A --> F[Web Thickness (Caliper)]

Summary: Measure 20 units using precise tools; ensure dimensions fall within specified tolerances to maintain block quality and uniformity.

IS 2185 (Part 1) - Classification of Concrete Blocks

Key Classification Details (Clause 5.2, Table 2):

• Grades indicate compressive strength (e.g., A(7.0) means 7 N/mm² average strength).
• Density is critical for classification: Hollow blocks generally have lower density than solid blocks.

Physical Requirements:

• Tests per Annex B-G ensure conformity.
• Sampling as per Clause 11.

Marking Requirements (Clause 14.3):

• Manufacturer ID
• Grade (e.g., A(7.0))
• Year of manufacture (if required)

Measurement Guidelines (Clause B-1.1):

• Dimensions measured with steel scale (1 mm accuracy).
• Face shell/web thickness with calipers (0.5 mm accuracy).
• Sample size: 20 full units.

Summary Formula for Compressive Strength Classification:

[ \text{Grade} \quad A(x) \quad \Rightarrow \quad \text{Average compressive strength} = x , \text{N/mm}^2 ]

flowchart TD
    A[Block Type] --> B[Hollow Load Bearing]
    A --> C[Solid Load Bearing]
    B --> D[Grades A(3.5) to A(15.0)]
    C --> E[Grades C(4.0), C(5.0)]
    D --> F[Density ≥ 1500 kg/m³ for A(8.5) and

IS 2185 (Part 1) - Materials and Mix Proportions Summary

1. Mix Proportion (Clause 7.1.1):

• Maximum concrete mix: 1 part cement : 6 parts combined aggregates (by volume).

2. Physical Requirements (Table 2, Clauses 5.1, 5.2, 9.4):

3. Testing & Marking (Clause 14.3):

• Testing cost borne by manufacturer if blocks fail; by purchaser if passed.
• Blocks must be permanently marked with:
  • Manufacturer ID
  • Grade (e.g., A(7.0))
  • Year of manufacture (if required)

4. Referenced Standards for Materials:

• Cement: IS 269 (33 grade), IS 455 (Portland slag), IS 1489 (Pozzolana), IS 8112 (43 grade), IS 12269 (53 grade)
• Aggregates: IS 383
• Admixtures: IS 9103
• Others: IS 3952 (burnt clay bricks), IS 456 (concrete practice)

Key Formula for Mix Design:

[ \text{Max Cement : Aggregate ratio} = 1 : 6 \quad \text{(by volume)} ]

flowchart TD

IS 2185 (Part 1) - Manufacturing & Curing Key Points

Drying Oven (Clause 2.2)

• Volume: ≥ 8 L per specimen, minimum total 50 L
• Air circulation: Fan for effective air movement
• Temperature: Constant at 50 ± 1°C
• Humidity: Controlled at ~17% RH using saturated calcium chloride solution
  • Solution exposed area ≥ 10 cm² per litre of oven volume
  • Solid CaCl₂ must remain above solution surface during test

Specimen Preparation (Clause 3.1)

• Sulphur capping:
  • Surface plane within 0.075 mm over 40 cm
  • Use 25 mm steel bars to form a mould ~12 mm larger than unit
  • Fill mould with 6 mm molten sulphur
  • Specimen axis ⟂ capping surface, hold until solidification
  • Cool caps ≥ 2 hours before testing
  • No patching allowed; defective caps replaced

Drying of Specimens

• Oven dry at 100°C to 115°C for ≥ 24 hours
• Dry until two consecutive weighings (2 h apart) differ by ≤ 0.2% mass

Testing Age (Clause 2.3)

• Specimens tested at 28 days from water addition

Summary Table: Drying Oven and Specimen Curing

flowchart TD
    A[Mix Dry Ingredients] --> B[Add Water]
    B --> C[Cast Specimen]
    C --> D[Apply Sulphur Capping]
    D --> E

IS 2185 Part 1: Surface Texture and Finish - Key Points

• Measurement Accuracy:

  • Length measurements after water removal: accuracy of 0.0025 mm using special apparatus (Clause 4.1).
  • Dry length measured adjacent to steel balls to nearest 1 mm (Clause 4.5).
  • Overall dimensions with steel scale graduated in 1 mm divisions (Clause 1.1).
  • Face shell and web thickness measured with caliper rule graduated in 0.5 mm divisions (Clause 1.1).

• Surface Preparation:

  • Bearing surfaces kept as per methods in Clauses D-3.1 and D-3.2 (Clause 3.0).

• Measurement Notes:

  • Length difference measured relative to an Invar reference length, not absolute length (Clause 4.1).
  • Minimum thickness checked for cored units (Clause 1.1).

Summary Table: Measurement Tools and Accuracy

flowchart LR
    A[Specimen Removal from Water] --> B[Wipe Grease from Steel Balls]
    B --> C[Measure Wet Length (±0.0025 mm)]
    C --> D[Dry Specimen]
    D --> E[Measure Dry Length Adjacent to Steel Balls (±1 mm)]
    E --> F[Measure Overall Dimensions & Thickness]

Note: Surface texture finish is controlled by maintaining bearing surfaces per Clause 3.0 and ensuring precise dimensional checks as above.

IS 2185 (Part 1) - Physical Requirements Summary

Key Specifications (Clause 5.2, Table 2)

Measurement & Testing (Clauses 1.1, 4.2, 9.4)

• Dimensions: Length, width, height measured with steel scale (1 mm gradation).
• Face shell/web thickness: Measured with calipers (0.5 mm gradation).
• **Compressive strength testing:

IS 2185 Part 1 – Sampling: Key Formulas & Specifications

Sampling Procedure (Clause 11.2)

• Take blocks at regular intervals during loading/unloading.
• If not practicable, sample randomly from stack:
  • From top surface,
  • Accessible sides,
  • Interior by opening trenches from the top.

Density Calculation (Clause 1.1)

• Dry 3 blocks to constant mass at ~100°C.
• Measure dimensions in cm (nearest mm).
• Compute volume (cm³).
• Weigh blocks (kg, nearest 10 g).
• Calculate density:

[ \text{Density} = \frac{\text{Mass (kg)}}{\text{Volume (cm}^3\text{)}} ]

Testing Speed (Clause 4.2)

• Apply load up to 50% max at any rate.
• Apply remaining load uniformly over 1 to 2 minutes.

Summary Table

flowchart TD
    A[Start Sampling] --> B{Loading/Unloading feasible?}
    B -- Yes --> C[Take blocks at regular intervals]
    B -- No --> D[Take random samples from stack]
    D --> E[Dry blocks at 100°C]
    E --> F[Measure dimensions & weight]
    F --> G[Calculate Density = Mass/Volume]
    G --> H[Apply Load: 50% any rate]
    H --> I[Apply remaining load over 1-2 mins]
    I --> J[Report results]

IS 2185 Part 1 — Testing Procedures: Key Points

1. Testing Machine (Clause 1.1: D-1.1)

• Use a machine capable of applying load uniformly.
• Control machine to ensure uniform rate of travel of moving head during loading.

2. Speed of Testing (Clause 4.2: D-4.2)

• Apply load up to 50% of expected max load at any convenient rate.
• Remaining load must be applied uniformly over 1 to 2 minutes.

3. Calculation and Reporting (Clause 9.4: Annex D)

• Compressive strength determined as:

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

Where:

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

4. Retesting Procedure (Clause 1.2: G-1.2)

• If any specimen exceeds limits in 9.7, test 3 additional specimens.
• Moisture and shrinkage tests repeated only if previous specimens failed.
• Dry specimens to constant length at 50 ± 1℃ before testing.

5. Rounding Off (IS 2:1960)

• Final results rounded to same significant figures as specified values.

Summary Table: Loading Rate

flowchart TD
    A[Start Loading] --> B{Load ≤ 50% Max Load?}
    B -- Yes --> C[Apply Load at Any Rate]
    B -- No --> D[Apply Remaining Load Uniformly]
    D --> E[Duration: 1 to 2 Minutes]
    C --> E
    E --> F[Record Max Load]
    F --> G[Calculate Compressive Strength]

This ensures consistent, reliable compressive strength testing as per IS 2185 Part 1.

IS 2185 Part 1: Criteria for Conformity Summary

Sampling & Testing (Clause 11.4.2)

• 20 blocks per lot:
  • 3 for density test (Clause 9.3)
  • 8 for compressive strength (Clause 9.4)
  • 3 for water absorption (Clause 9.5)
  • 3 for drying shrinkage (Clause 9.6) & moisture movement (Clause 9.7)
  • 3 reserved for retests (drying shrinkage & moisture movement)

Conformity Condition (Clause 12.1)

• Lot is conforming if tests satisfy criteria in Clauses 12.2 to 12.5.

Physical Requirements Table (Clause 5.2 & Table 2)

Measurement Specifications (Clause B-1.1)

• Overall dimensions: steel scale, 1 mm divisions.
• Face shell/web thickness: caliper, 0.5 mm divisions, jaw length 15–25 mm.
• 20 full-size units measured for length, width, height, and thickness.

Key Notes:

• Compressive strength tests must meet minimum average and minimum individual values.
• Density is critical for grade classification.
• Sampling and

Manufacturer's Certificate - IS 2185 (Part 1): Key Points

• Clause 13: Manufacturer must ensure masonry units conform to IS 2185 Part 1 requirements.
• Certificate: On request, a certificate confirming conformity must be supplied to purchaser or representative.
• Testing: Tests per Annex B-G and sampling per Clause 11 ensure compliance.
• Clause 14.2: Manufacturer provides free test samples.

Key Specifications & Tables for Masonry Units

Measurement Tools (Clause 1.1)

• Dimensions: Steel scale with 1 mm divisions.
• Face shell/web thickness: Caliper with 0.5 mm divisions, jaw length 15-25 mm.
• Sample size: 20 full-size units for length, width, height; cored units for minimum thickness.

Water Absorption (Clause 12.5)

• Mean water absorption ≤ maximum limit in Clause 9.5 (typically ≤ 15% by weight).

flowchart TD
    A[Manufacturer] --> B[Ensures conformity to IS 2185]
    B --> C[Supplies Manufacturer's Certificate]
    B --> D[Provides samples for independent testing]
    D --> E[Testing per Annex B-G & Clause 11]
    E --> F[Test results confirm compliance]

Summary: Manufacturer

IS 2185 (Part 1) - Independent Tests Key Points

1. Number of Tests (Clause 11.4)

• Tests are conducted on samples selected per Clause 11 sampling.
• Ensure units conform to physical requirements in Clause 9.

2. Testing Machine (Clause 1.1)

• Use a machine capable of applying load uniformly and controlling speed.

3. Speed of Testing (Clause D-4.2)

• Apply load up to 50% of expected max load at any convenient rate.
• Then apply remaining load uniformly in 1 to 2 minutes by controlling moving head speed.

4. Physical Requirements & Compressive Strength (Table 2, Clause 5.2)

5. Calculation & Report (Clause D-5)

• Calculate compressive strength as load divided by cross-sectional area.
• Report average and individual unit strengths.
• Moisture movement and other physical tests per Annex B-G.

Summary Formula for Compressive Strength:

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

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

flowchart LR
    A[Select Samples per Clause 11] --> B[Test Units per Annex B-G]
    B --> C