Code of practice for the use of silicate-type chemical-resistant mortars

IS 4441: Scope & Key Specifications for Silicate Type Chemical Resistant Mortars

Scope (Clause 2.1 and 0.2):

• Applies to silicate type chemical resistant mortars used as bonding materials in acid-resistant flooring and jointing of acid-proof bricks/tiles.
• Suitable for acids like nitric, chromic, sulphuric, hydrochloric (pH ≤ 4).
• Not suitable for hydrofluoric acid, concentrated orthophosphoric acid, alkalies, boiling water, steam, or frequent water washing.
• Chemical resistance depends on acid concentration; weak acids (pH > 4) degrade mortar strength and resistance.

Chemical Resistance Table (Clause 7.1, Table 1)

Legend:

• R = Generally recommended
• L = Limited use (occasional spillage)
• N = Not recommended

Important Notes:

• Mortars develop resistance through chemical bonding with acids; exposure to acids with pH > 4 reduces effectiveness.
• Not recommended for continuous exposure to weak acids or frequent water washing areas.
• For questionable conditions, consult mortar manufacturer.

IS 4441: Definitions & Key Specifications for Silicate Type Chemical Resistant Mortars

Clause 2.0: Definitions

• Defines terms related to silicate type chemical resistant mortars for uniform understanding.

Chemical Resistance (Clause 7.1 & Table 1):
Silicate mortars are classified by their resistance to chemicals in immersion at ambient temperature:

Legend:

• R = Generally Recommended
• L = Limited Use (occasional spillage)
• N = Not Recommended

Additional Notes:

• Silicate mortars develop resistance via acid reaction; effective only if acid pH ≤ 4.
• Not suitable for weak acids (pH > 4), alkalies, boiling water, or frequent washing.
• Application differs for floors and walls with specified joint thickness.
• Rounding of numerical values per IS:2-1960.

flowchart LR
    A[Chemical Exposure] --> B{Type of Chemical}
    B -->|Acids (pH ≤ 4)| C[Use Silicate Mortar]
    B -->|Acids (pH > 4), Alkalies| D[Not Suitable

IS 4441: Storage and Handling of Silicate Type Chemical Resistant Mortars

Key Specifications:

• Filler Storage (Clause 3.1):

  • Must be protected from water.
  • Preferably stored under a roof.
  • If not possible, keep in original containers under a waterproof cover.

• Liquid Binder Storage (Clause 3.2):

  • Must be protected from freezing.
  • If frozen, thaw and remix thoroughly before use.
  • Use only if original consistency is restored.

Additional Notes:

• This standard complements IS 4832 (Part I)-1969 for chemical resistant mortar requirements.
• Emphasizes proper storage to maintain material integrity for effective mortar performance.

Summary Table:

flowchart LR
    A[Filler Storage] --> B{Under roof?}
    B -- Yes --> C[Store dry]
    B -- No --> D[Keep in original container + waterproof cover]

    E[Liquid Binder Storage] --> F{Freezing?}
    F -- No --> G[Store above freezing]
    F -- Yes --> H[Thaw + Remix]
    H --> I{Consistency restored?}
    I -- Yes --> J[Use]
    I -- No --> K[Reject]

This ensures mortar quality and durability per IS 4441 guidelines.

IS 4441: Mixing of Silicate Mortar – Key Points & Specifications

• Mixing Procedure (Clause 4.3):

  1. Add ~75% of filler to liquid binder in a clean container.
  2. Mix with a trowel until a paste forms.
  3. Add remaining filler and mix until uniform mortar is achieved.

• Batch Size (Clause 4.4):

  • Only mix the quantity of mortar that can be used before it sets.
  • Setting time varies with temperature; site personnel must judge batch size accordingly.

• Temperature Precautions (Clause 4.7):

  • For mixing/application at <10℃ or >27℃, consult manufacturer for special instructions.

• Additional Reference:

  • Composition and requirements of silicate mortars are detailed in IS 4832 (Part I) - 1969.

Practical Notes:

flowchart LR
    A[Start: Liquid Binder] --> B[Add 3/4 Filler]
    B --> C[Mix to form Paste]
    C --> D[Add Remaining Filler]
    D --> E[Mix to Uniform Mortar]
    E --> F[Use before Setting Time Expires]

This ensures proper consistency and workability of silicate mortars per IS 4441.

IS 4441: Surface Preparation & Application for Chemical Resistant Mortars

1. Surface Preparation (Clause 5.1 & 5.1.1)

• Surface must be clean, dry, and cured before laying bricks/tiles (IS:4860-1968 / IS:4457-1967).
• Apply bitumen primer (IS:158-1981) on prepared surface.
• Follow with a uniform coat of bitumen (IS:1580-1969).
• For epoxy/polyester resin bedding, bricks/tiles can be laid directly without primer.
• For furane, cashewnut shell liquid, phenolic resins, use bitumen primer depending on service conditions.
• Alternative membranes: rubber, lead, poly isobutane, fibre reinforced plastics.

2. Chemical Resistance Table (Clause 7.1)

Legend:

• R = Generally Recommended
• L = Limited Use (occasional spillage)
• N = Not Recommended

Summary Diagram of Surface Preparation Process

Key Specifications and Procedures for Curing of Mortar Joints (IS 4441)

1. Acid Curing (Clause 6.1)

• Acid Types & Concentrations:
  • Hydrochloric acid: 20–25%
  • Sulphuric acid: 30–40%
• Timing:
  • Apply acid curing not earlier than 2 days and not later than 6 days after bonding.
• Duration: Minimum 60 minutes.
• Preparation Notes:
  • Acid solution must be prepared by adding acid to water (not vice versa).
  • Sulphuric acid solution must be prepared outside the unit.
• Safety: Use aprons, gloves, boots, etc.

2. Mixing Acid Solutions (Note in 6.1)

3. Curing Time Before Use (Clause 6.3)

• Non-silicate mortars: Minimum 48 hours after bonding.
• Silicate mortars with acid curing: Minimum 24 hours after acid curing.
• Protect from rain/water during curing.

4. When Acid Curing is Not Required (Clause 6.2)

• If bedding is silicate mortar and jointing is epoxy, polyester, or sulphur mortar → No acid curing needed.
• If jointing is phenolic, furane, or cashewnut shell liquid → Acid curing as per 6.1 before jointing.

5. Joint Preparation (Clause 5.3.1)

• Mortar thickness: 6–8 mm.
• Joint width: max 6 mm.
• Remove mortar from joints to 20 mm depth before jointing.
• Fill joints fully after acid curing.

flowchart TD
    A[Bonding of Masonry Units] --> B{Wait 2 to 6

Chemical Resistance of Silicate Type Mortars (IS 4441: Clause 7.1)

Key points:

• Chemical resistance is rated for immersion at ambient temperature.
• Ratings can be upgraded for spillage exposure.
• Testing method per IS 4456 (Part I)-1967.

Chemical Resistance Table (Summary)

Legend:

• R = Generally Recommended
• L = Limited Use (occasional spillage)
• N = Not Recommended

Additional Notes:

• Joint thickness and application methods differ for walls and floors.
• Cure times vary: at least 24 hours after acid curing for silicate mortars.
• Protect from rain/water during curing.
• Consult manufacturer for questionable

IS 4441: Precautions and Safety Measures for Silicate Type Mortars

Key Specifications & Precautions:

• Storage of Filler (Clause 3.1):

  • Protect filler from water.
  • Store under roof or in original containers with waterproof cover.

• Temperature Precautions (Clause 4.7):

  • Avoid mixing, application, or setting below 10°C or above 27°C.
  • Consult manufacturer for special recommendations if outside this range.

• Chemical Resistance (Clause 7.1 & Table 1):

  • Chemical resistance varies by mortar type (Sodium Silicate or Potassium Silicate).
  • Ratings:
    • R = Recommended for immersion
    • L = Limited use (occasional spillage)
    • N = Not recommended
  • Examples:

    Substance	Sodium Silicate	Potassium Silicate
    Hydrochloric Acid (conc.)	R	R
    Sulphuric Acid (10-50%)	L	R
    Hydrofluoric Acid (any)	N	N
    Sodium Hydroxide (any)	N	N

Summary:

• Store materials dry and protected.
• Maintain temperature between 10°C and 27°C during handling.
• Refer to chemical resistance table for mortar selection based on exposure.
• Always consult the manufacturer for unusual conditions.

flowchart TD
    A[Storage] --> B[Protect filler from water]
    B --> C[Store under roof or waterproof cover]
    D[Temperature] --> E[Mixing/Application between 10°C-27°C]
    E --> F[Consult manufacturer if outside range]
    G[Chemical Resistance] --> H[Select mortar type based on exposure]
    H --> I[Use Table 1 for guidance]

This ensures safety and durability of silicate mortars as per IS 4441.