Methods of physical tests for hydraulic cement, Part 8: Determination of transverse and compressive strength of plastic mortar using a prism

IS 4031 Part 8 - Scope: Key Specifications & Tables

Scope:
IS 4031 Part 8 specifies test methods for hydraulic cement, focusing on apparatus and procedures for determining properties like compressive strength.

Key Specifications:

• Scraper (Clause 4.6):

  • Rubber blade semi-rigid, 75 mm long × 50 mm wide
  • Tapered edge thickness: ~2 mm
  • Handle length: ~150 mm

• Planetary mixer & Jolting apparatus:

  • Standardized equipment for cement and pozzolana testing (details per IS 4031 Part 8).

Important Table: Permissible Variations on Weights (Clause 4.2)

Additional Notes:

• Rounding off (Clause 0.4): Use IS 2-1960 for rounding test results to the same significant figures as specified values.
• Typical Jig Components (Clause 9.2): Includes ball bearings, sliding assembly, springs, spherical seating, upper/lower platens of jig and machine (see Fig. 2 in IS 4031 Part 8).

This scope ensures standardized apparatus and procedures for cement testing, critical for quality control in construction materials.

IS 4031 Part 8: Sampling and Selection of Test Specimens for Plastic Mortar Strength

Key Points from IS 4031 Part 8:

• Scope: Covers procedure for determining transverse and compressive strength of plastic mortar using prism specimens.

• Sampling & Moulding (Clause 7.1):

  • Specimens are moulded into prisms of standard dimensions as per the code.
  • Proper compaction and curing are essential for valid results.

• Apparatus & Weights (Clause 4.2):
  Permissible variations on standard weights used in weighing cement:

• Typical Test Setup (Fig. 2):
  Includes upper/lower platens, spherical seating, ball bearings, sliding assembly, and return spring for compressive strength testing.

Calculation Formula (Clause 9.2):

• Compressive Strength, ( f_c ):

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

Where:

• ( P ) = Maximum load applied (N)
• ( A ) = Cross-sectional area of the specimen (mm²)

Summary:

• Use standard prisms moulded as per Clause 7.1.
• Weigh cement with permissible weight variations (Table 1).
• Test using the jig setup (Fig. 2) for compressive strength.
• Calculate strength using ( f_c = P/A ).

flowchart TD
    A[Sampling of Plastic Mortar] --> B[Moulding into Prisms]
    B --> C[Curing as per IS]
    C --> D[Testing in Compressive Strength Jig]
    D --> E[Measure Load P

IS 4031 Part 8: Temperature and Humidity Requirements

• Moulding Room, Dry Materials & Water:

  • Temperature: 27 ± 2°C
  • Relative Humidity: 65 ± 5%

• Moist Closet / Moist Room:

  • Temperature: 27 ± 2°C
  • Relative Humidity: ≥ 90%

• Specimen Handling:

  • After moulding, cover specimens with steel/rubber sheets.
  • Store in moist room/cabinet at 27 ± 2°C and ≥ 90% RH until demoulding to prevent evaporation.

Summary Table

Notes:

• Maintaining these conditions ensures consistent hydration and curing of cement specimens.
• Sampling per IS 3535-1986 ensures representative cement samples for testing.

flowchart LR
    A[Moulding Room] -->|27±2°C, 65±5% RH| B[Moulding & Covering]
    B -->|Cover with steel/rubber sheet| C[Moist Room]
    C -->|27±2°C, ≥90% RH| D[Demoulding & Curing]

IS 4031 (Part 8) - Apparatus Key Details

1. Jolting Apparatus (Clause 4.5)

• Must conform to IS: 10078-1982.
• Used for compacting cement paste in molds by jolting action.

2. Standard Weights (Clause 4.2 & Table 1)

Permissible variation on weights used for weighing cement:

3. Scraper (Clause 4.6)

• Semi-rigid rubber blade attached to a handle (~150 mm long).
• Blade dimensions: ~75 mm long, 50 mm wide, tapering to 2 mm thick edge.

4. Typical Jig for Compressive Strength Test (Clause 9.2)

• Comprises ball bearings, sliding assembly, return spring, spherical seating, upper/lower platens of jig and machine.
• Ensures uniform load application during testing.

Summary Diagram: Apparatus Components

flowchart TD
    A[Jolting Apparatus] --> B[Conforms to IS:10078-1982]
    C[Weights] --> D[Permissible Variations (Table 1)]
    E[Scraper] --> F[Semi-rigid rubber blade]
    G[Jig for Compressive Strength] --> H[Ball bearings]
    G --> I[Sliding assembly]
    G --> J[Return spring]
    G --> K[Spherical seating]
    G --> L[Upper & Lower Platens]

Use this apparatus with specified tolerances for accurate cement testing per IS 4031 (Part 8).

IS 4031 Part 8: Composition of Mortar - Key Specifications

• Mix Proportions by Mass (Clause 5.1):

  • Cement : Standard Sand : Water = 1 : 3 : 0.5 (w/c ratio)
  • Standard sand conforms to IS 650-1966
  • Water used should be potable or distilled

• Quantities for 3 Test Specimens (Clause 6.1):

  • Cement = 450 g
  • Sand = 1350 g (usually 3 equal fractions of coarse, medium, fine sand)
  • Water = 225 g

• Mixing:

  • Mechanical mixing as per Clause 4.3
  • Use demoulding device as per Fig. 1 (Clause 4.7)

• Strength Testing (Clause 9.1):

  • Flexural and compressive strength in N/mm²
  • Test on at least 3 prisms per age
  • Avoid more than 2 prisms from same batch per age

Summary Table: Mortar Mix Composition

flowchart LR
    Cement -->|1 part| MortarMix
    Sand -->|3 parts| MortarMix
    Water -->|0.5 part| MortarMix
    MortarMix --> Mixing[Mechanical Mixing]
    Mixing --> Testing[Strength Testing on 3 prisms]

This ensures consistent mortar for strength tests as per IS 4031 Part 8.

IS 4031 Part 8: Preparation of Mortar - Key Points

1. Mortar Proportions (Clause 5.1)

• Cement : Standard Sand : Water = 1 : 3 : 0.5 (by mass)
• Water-cement ratio = 0.50
• Standard sand as per IS 650-1966
• Use potable or distilled water

2. Mixing Procedure (Clause 6.1.1)

• Pour water → add cement
• Start mixer at 140-150 rpm for 30s
• Add fine, medium, coarse sand fractions steadily over next 30s
• Increase mixer speed to 285 ± 10 rpm, mix 30s
• Stop mixer for 1 min 30s:
  • First 15s: scrape mortar from bowl walls, mix back
  • Cover bowl for remaining 1 min 15s
• Resume mixing at 285 ± 10 rpm for 1 minute

3. Mix Quantities for 3 Specimens (Clause 6.1)

4. Demoulding Device

• Use apparatus as per Fig. 1 (IS 4031 Part 8) for specimen demoulding.

flowchart TD
    A[Add Water to Mixer] --> B[Add Cement]
    B --> C[Mix at 140-150 rpm for 30s]
    C --> D[Add Sand Fractions (fine → medium → coarse) over 30s]
    D --> E[Mix at 285 ± 10 rpm for 30s]
    E --> F[Stop Mixer for 1 min 30s]
    F --> G[Scrape bowl walls for 15s]
    G --> H[Cover bowl for 1 min 15s]
    H --> I[Mix at 285 ± 10 rpm for 1 min]

This ensures uniform mortar consistency and reproducibility in cement testing.

IS 4031 Part 8: Preparation and Curing of Test Specimens

Key Specifications:

1. Mixing Procedure (Clause 6.1.1)

• Pour water into mixer bowl.
• Add cement.
• Start mixer at low speed: 140 ± 5 rpm for 30 s.
• Add fine, medium, coarse sand fractions steadily over next 30 s.
• Switch to medium speed: 285 ± 10 rpm, mix for 30 s.
• Stop mixer for 1 min 30 s:
  • During first 15 s, scrape mortar from bowl walls into center.
  • Cover bowl for remaining 1 min 15 s.
• Resume medium speed mixing for 1 min.

2. Curing of Specimens (Clause 7.2.3)

• After demoulding, cure specimens by immersion in water at 27 ± 2°C.
• Keep vertical faces vertical; specimens separated for free water access.
• Change water every 14 days.
• Remove specimens from water less than 15 min before testing.
• Transport specimens in water-filled container.
• Wipe specimens clean before testing.

Summary Table for Curing Conditions

flowchart TD
    A[Mixing] --> B[Demoulding]
    B --> C[Curing in water at 27±2°C]
    C --> D[Water replaced every 14 days]
    D --> E[Specimens removed <15 min before test]
    E --> F[Testing]

This ensures consistent hydration and reliable test results for cement mortar specimens.

IS 4031 Part 8: Test Procedures – Key Formulas, Tables & Specifications

1. Test Setup Components (Clause 9.2 & Fig. 2)

• Ball bearings, sliding assembly, return spring, spherical seating, upper & lower platens of jig and machine ensure uniform load application during compressive strength testing.

2. Permissible Variations on Weights (Clause 4.2, Table 1)

3. Rounding Off Results (Clause 0.4)

• Round off test results as per IS 2-1960.
• Maintain the same number of significant digits as specified in the standard.

4. Curing of Test Specimens (Clause 7.2)

• Test specimens must be cured under specified conditions to ensure consistent strength results.

Summary Diagram: Compressive Strength Test Setup

graph TD
    A[Upper Platen of Machine] --> B[Spherical Seating of Machine]
    B --> C[Upper Platen of Jig]
    C --> D[Ball Bearings]
    D --> E[Sliding Assembly]
    E --> F[Return Spring]
    F --> G[Spherical Seating of Jig]
    G --> H[Lower Platen of Jig]
    H --> I[Lower Platen of Machine]

Note: Always verify calibration of weights and apparatus before testing to ensure accuracy and compliance with IS 4031 Part 8.

IS 4031 Part 8 — Key Calculations & Specifications for Compressive Strength Testing

Load Application (Clause 8.2.1)

• Load increase rate: 1 N/mm² per second up to ~half the expected crushing load.
• Test duration: ≥ 10 seconds (can be longer if load rate is higher).

Calculation Essentials (Clause 9.2 & Table 9)

• Components considered in calculations:
  • Ball bearings
  • Sliding assembly
  • Return spring
  • Spherical seating (machine & jig)
  • Upper & lower platen (machine & jig)

Compressive Strength Formula

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

Where:

• (f_c) = Compressive strength (N/mm²)
• (P) = Maximum load at failure (N)
• (A) = Cross-sectional area of specimen (mm²)

Permissible Weight Variations for Weighing Cement (Table 1, Clause 4.2)

Rounding Off (Clause 0.4)

• Round final test results as per IS 2:1960.
• Retain significant figures equal to the specified value.

flowchart TD
    A[Start Test] --> B[Apply Load @ 1 N/mm²/s]
    B --> C{Load = 0.5 × Expected Crushing Load?}
    C -- No --> B
    C -- Yes --> D[Continue Load Application]
    D --> E[Record Peak Load P]
    E --> F[Calculate Compressive Strength \(f_c = P/A\)]
    F --> G[