Code of Practice for Preparation and Use of Masonry Mortars

IS 2250 - Scope Overview

IS 2250 covers the code of practice for preparation and use of masonry mortars. It defines materials, mixing, testing, and application methods.

Key Points from the Scope:

• Clause 6.4: Record the maximum load at failure during testing of mortar samples.

• Clause 2.0: Definitions align with IS 6508-1972 (testing of cement mortar) and IS 4305-1967 (sand for masonry mortars).

• Clause 2.1: Scales for weighing materials must meet accuracy requirements to ensure correct mix proportions.

• Clause 2.2: Flow Table test as per IS 5512-1969 is used to assess mortar consistency.

Important Specifications:

Typical Mortar Mix Proportions (by volume):

flowchart LR
    A[Material Weighing] --> B[Mixing Mortar]
    B --> C[Flow Table Test (IS 5512)]
    C --> D[Apply Mortar in Masonry]
    D --> E[Test Load at Failure]

Summary: IS 2250 ensures mortar quality by standardizing material measurement, consistency testing, and strength evaluation.

IS 2250 - Definitions & Key References

• Clause 2.0: Definitions supplement those in IS 6508:1972 (Rubber Mouldings) and IS 4305:1967 (Rubber Testing).

• Flow Table (Clauses 2.2 & 2.6): Refer to IS 5512:1969 for the Flow Table used in testing workability of rubber compounds. This table provides standard flow values for different compound types.

• Maximum Load at Failure (Clause 6.4): The maximum load recorded during testing is critical to assess material strength.

Key Notes:

Typical Flow Table (from IS 5512):

(Exact values depend on compound specifics)

Summary:

• Use IS 6508 & IS 4305 for base definitions.
• Use IS 5512 for flow properties.
• Record maximum load at failure per Clause 6.4.

flowchart LR
    A[IS 2250 Definitions] --> B[IS 6508: Rubber Mouldings]
    A --> C[IS 4305: Rubber Testing]
    A --> D[IS 5512: Flow Table]
    D --> E[Flow Value for Compound]
    F[Testing] --> G[Max Load at Failure]

IS 2250: Necessary Information - Key Formulas, Tables, and Specifications

1. Maximum Load at Failure

• As per Clause 6.4, record the maximum load at failure during testing for design validation.

2. Mortar Grades & Mix Proportions (Clause 1.5 & 5.3.2)

• Mortar grades are defined by cement, lime, pozzolana, and sand proportions (by loose volume).
• Compressive strength at 28 days varies by mortar grade.

Sample Table: Grade of Masonry Mortars

3. Flow Table Reference

• Use IS 5512-1969 for flow table data related to mortar consistency and workability (Clause 2.2).

Summary Diagram (Mermaid.js)

flowchart TD
    A[Start: Select Mortar Grade] --> B{Choose Mix Proportions}
    B --> C[Cement]
    B --> D[Lime]
    B --> E[Pozzolana]
    B --> F[Sand]
    C & D & E & F --> G[Calculate Compressive Strength]
    G --> H[Refer IS 2250 Tables]
    H --> I[Record Max Load at Failure]

Note: Always verify mix proportions and compressive strength with site tests and IS 2250 guidelines.

IS 2250: Materials for Masonry Mortars — Key Specifications

1. Grades of Mortar & Mix Proportions (by loose volume)

• Lime classes (A, B, C, D, E) refer to IS 712:1973.
• LP-20, LP-40: Lime-Pozzolana mixtures with 20% or 40% pozzolana.
• Compressive strength measured as per Appendix A of IS 2250.

2. Notes:

• Mortar strength depends on mix and curing.
• Lime pozzolana mixtures improve durability.
• Cement used should conform to IS 269 (Ordinary Portland Cement).

3. Compressive Strength Test (Appendix A)

• Mortar cubes 70.6 mm tested at

Durability and Hardening of Mortars (IS 2250)

Key Factors Affecting Durability (Clause 5.1.1)

• Volumetric changes during setting, hardening, temperature, and moisture variations.
• Crack nature and distribution: fine distributed cracks are preferable over large localized cracks.
• Bond integrity: mortar-to-unit bond should resist rupture to prevent strength loss and water seepage.
• Chemical resistance: mortar must resist aggressive environmental attacks.

Mortar Grades & Compressive Strength (Clause 5.3.2, Table 6)

• Lime classes A, B, C, D, E per IS 712.
• Pozzolana reactivity ≥ 4 N/mm².
• Compressive strength tested as per Appendix A of IS 2250.

Notes:

• Mortar mix proportions are by loose volume.
• Strength values are for wet-ground mortar ingredients.
• Use ordinary Portland cement as per IS 269 for cement-pozzolana mixes.

flowchart LR
    A[Durability Factors] --> B[Volumetric Changes]
    A --> C[Crack Distribution]
    A --> D[Bond Integrity]
    A --> E[Chemical

IS 2250: Grade of Mortar Summary

Key Points from Clause 5.3.2 & Table 1

• Grade Definition: Mortar grade is defined by its 28-day compressive strength (N/mm²).
• Mortar mixes are given by loose volume proportions of Cement, Lime, Pozzolana, and Sand.
• Lime Pozzolana Mixture (LP) is used in some mixes, e.g., LP-20, LP-40.

Typical Grades & Mix Proportions (Loose Volume)

Notes:

• LP-20 and LP-40: Lime-Pozzolana mixtures with specific proportions (20% or 40% Pozzolana).
• Compressive strength testing follows Appendix A procedure.
• Lime types (A, B, C, D, E) refer to different qualities as per IS standards.
• Mix proportions vary based on mortar strength requirements and materials.

Compressive Strength Testing

• Determined on mortar cubes/cylinders at 28 days.
• Standard procedure ensures uniformity in grade classification.

flowchart LR
    A[Raw Materials] --> B[Cement]
    A --> C[Lime]
    A --> D[Pozzolana

Criteria for Selection of Masonry Mortars (IS 2250)

Key Points (Clause 7.1 & Table 1):

• Selection depends on loading and exposure conditions.
• Mortars are classified by grade, defined by minimum compressive strength at 28 days.
• Mortar mix proportions are given by loose volume of Cement, Lime, Pozzolana, and Sand.
• Lime classes A, B, C, D, E refer to IS 712.
• Pozzolana must have minimum lime reactivity of 4 N/mm².

Table 1: Grade of Masonry Mortars (Summary)

Important Notes:

• Pozzolana-lime mixtures are expressed as LP-7, LP-20, LP-40 indicating lime-pozzolana volume ratios.
• Compressive strength testing follows Appendix A procedure.
• Ordinary Portland Cement should conform to IS 269.

Formula for approximate cement-pozzolana ratio by weight:

[ \text{Cement : Pozzolana} \approx 0.8 : 0.2 ]

Summary diagram of mortar selection factors:

flowchart TD
    A[Loading & Exposure] --> B[Mortar Grade Selection]
    B --> C[Mix Proportion: Cement, Lime, Pozzolana, Sand]
    C --> D[Compressive Strength @ 28 days]
    D --> E[Durability

IS 2250: Preparation of Masonry Mortars – Key Points

1. Grades & Mix Proportions (Table 1, Clause 5.3.2 & 6.1)

Masonry mortars are classified by minimum 28-day compressive strength (N/mm²) and mix proportions by loose volume:

• Lime classes A, B, C, D, E as per IS 712-1973.
• Pozzolana must have minimum lime reactivity of 4 N/mm².
• Strength tested per Appendix A procedure.

2. Unit Weights for Volume-Weight Conversion (Table 2, Clause 8.1.1)

• Loose condition = poured without compaction.

3. Notes:

• Mortar strength depends on wet grinding of ingredients.
• Cement-pozzolana ratio by volume ~0.8:0.2 corresponds to weight ratio.
• Ordinary Portland Cement as per IS 269-1976.

Summary Formula for Mortar Mix by Loose Volume:

[ \text{Mortar Mix

IS 2250 Key Points on Consistency & Workability of Mortar

Consistency (Clauses 2.5, 9.1)

• Defined by the worker’s judgment during application.
• Should maintain fluidity for ease of spreading without causing segregation.
• Water content depends on:
  • Type of masonry units (e.g., burnt clay or concrete blocks require good water retention).
  • Joint thickness (thinner joints need higher fluidity).
  • Load conditions (heavily loaded joints require stiffer mortar).
• Water retentivity is critical to prevent rapid suction by masonry units.

Workability (Clause 2.9)

• Ease of mixing, placing, compacting, and finishing mortar.
• Related to the energy required to overcome internal friction and achieve full consolidation.

Re-Tempering (Clause 8.6.1)

• Water can be added to stiffened mortar within 60 minutes of cement addition to restore workability.

Typical Water Content Guidelines for Mortar (Indicative)

Summary Formula for Water Requirement:

[ W = f(\text{masonry unit absorption}, \text{joint thickness}, \text{desired fluidity}) ]

Where W = water content (liters per 50 kg cement)

flowchart LR
    A[Mixing Mortar] --> B[Check Consistency]
    B -->|Too stiff| C[Add Water]
    B -->|Too fluid| D[Add Dry Mix]
    C --> E[Apply Mortar]
    D --> E
    E --> F[Workability: Easy to place & finish]

Note: IS 2250 emphasizes practical judgment over strict numeric values for consistency and workability; adjustments are made on-site based on material behavior.

IS 2250: Sampling of Freshly Mixed Masonry Mortars

Key Points from Clause 10 (Sampling):

• Sample Size & Method:
  Collect representative samples immediately after mixing. Use clean containers to avoid contamination.

• Marking & Records (Clause 10.3):

  • Place & method of sampling
  • Date of preparation
  • Quantity of batch/consignment

Water Retentivity (Clause 9.2 & Appendix C):

• Used when masonry units have high suction.
• Water retentivity test:
  [ \text{Flow after suction} \geq 70% \times \text{Flow before suction} ]

Mortar Grades & Mix Proportions (Table 1, Clause 5.3.2):

Summary Diagram for Sampling Process:

flowchart TD
    A[Freshly Mixed Mortar] --> B[Sampling Immediately]
    B --> C[Mark Sample Container]
    C --> D[Record Details]
    D --> E[Testing: Water Retentivity & Strength]

Use IS 2250 Appendix A for compressive strength testing procedures and Appendix C for water retentivity tests.

IS 2250: Determination of Compressive Strength of Masonry Mortar

Key Points from Clause 6.1 & Table 1 (Grade of Mortars)

• Mortars are specified by grade based on minimum compressive strength at 28 days.
• Compressive strength is tested as per Appendix A procedure.
• Mortar mix proportions are by loose volume of Cement, Lime, Pozzolana, and Sand.

Notes:

• Lime classes A-E as per IS 712:1973.
• Pozzolana must have minimum lime reactivity of 4 N/mm².
• Wet grinding of ingredients improves strength.
• Cement-Pozzolana ratio approx. 0.8:0.2 by weight for some mixes.

Compressive Strength Test (Appendix A summary):

• Prepare mortar cubes (usually 70.6 mm size).
• Cure for 28 days under standard conditions.
• Test in compression machine; calculate strength as:

[ 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)

flowchart TD
    A[Prepare mortar mix as per grade] --> B[Cast cubes (70.6 mm)]
    B --> C[Cure for 28 days]
    C

IS 2250: Determination of Consistency of Masonry Mortar

Key Clauses:

• Clause 1.1 & B-1.1: Purpose is to determine mortar consistency.
• Appendix B (Clause 9.1.1 & 4.1): Procedure for consistency test.
• Clause 8.1 & Appendix C: Related to water retentivity, affecting consistency.

Consistency Test Method (Appendix B):

• Objective: Find the water content at which mortar attains a standard flow.
• Procedure:
  • Prepare mortar with varying water content.
  • Use a flow table or flow cone test.
  • Measure flow diameter or flow time.
  • Average of two tests reported as consistency.

Typical Flow Table Test (IS 2250):

Consistency is considered optimum when flow diameter is about 110 mm.

Water Retentivity (Appendix C):

• Indicates mortar's ability to retain water.
• Important for proper hydration and bond strength.

Summary:

• Consistency: Water content at which mortar flows to ~110 mm diameter.
• Test: Flow table method, average of two tests.
• Water Retentivity: Ensures mortar doesn't lose water too fast.

flowchart LR
    A[Prepare mortar mix] --> B[Add varying water content]
    B --> C[Test flow on flow table]
    C --> D[Measure flow diameter]
    D --> E{Flow ~110 mm?}
    E -- Yes --> F[Report water content as consistency]
    E -- No --> B

This ensures mortar consistency suitable for masonry work as per IS 2250.

IS 2250: Water Retentivity of Masonry Mortar (Appendix C)

Purpose

• To measure the ability of mortar to retain water against suction and evaporation.
• Important for mortars used with high-suction masonry units.

Key Specification

• After suction, the flow of mortar shall not be less than 70% of the flow before suction.

Test Procedure (Summary)

1. Prepare fresh mortar and place on a standard flow table.
2. Measure initial flow (before suction).
3. Apply a specified suction to the mortar sample.
4. Measure flow after suction.
5. Calculate water retentivity as:

[ \text{Water Retentivity} = \frac{\text{Flow after suction}}{\text{Flow before suction}} \times 100% ]

Acceptance Criteria

• Water Retentivity ≥ 70%

Flow Table Dimensions (Typical)

Summary Diagram

flowchart LR
    A[Prepare Mortar Sample] --> B[Place on Flow Table]
    B --> C[Measure Initial Flow]
    C --> D[Apply Suction]
    D --> E[Measure Flow After Suction]
    E --> F[Calculate Water Retentivity]
    F --> G{Retentivity ≥ 70%?}
    G -- Yes --> H[Mortar Suitable]
    G -- No --> I[Modify Mix]

Note: This test indirectly measures workability and water retention, critical for bond strength and durability in masonry construction.