Code of practice Concrete structures for the storage of liquids, Part 1: General requirements

IS 3370 Part 1: Scope & Key Specifications

Scope:

• Covers design and construction of concrete structures for water tanks.
• Excludes: dams, pipes, pipelines, lined structures, and damp-proofing of basements.

Key Specifications (Clause 5(a), Foreword)

Durability (Clause 6.1)

• Concrete mix design must ensure durability.
• Limits on water-cement ratio and cement content are critical for durability.
• Minimum cement content and max water-cement ratio ensure resistance against water penetration and chemical attack.

Summary:

• Use M30 grade or above for reinforced concrete water tanks.
• Maintain water-cement ratio ≤ 0.45 for reinforced concrete.
• Cement content ≥ 320 kg/m³ for reinforced concrete.

flowchart LR
    A[Scope] --> B[Concrete Water Tanks]
    A --> C[Excludes Dams, Pipes, Basements]
    B --> D[Concrete Types]
    D --> E[Plain Concrete: M20, 250kg/m³, 0.50 W/C]
    D --> F[Reinforced Concrete: M30, 320kg/m³, 0.45 W/C]
    D --> G[Prestressed Concrete: M40, 360kg/m³, 0.40 W/C]

This ensures structural integrity and durability for water retaining structures per IS 3370 Part 1.

IS 3370 Part 1: Referenced Standards & Key Specifications

• Referenced Standards:

  • IS 11682: Design criteria for RCC staging of overhead water tanks.
  • IS 456: General code for plain and reinforced concrete construction.
  • IS 1343: Code for prestressed concrete structures.
  • These are mandatory unless otherwise specified.

• Durability & Concrete Quality (Table 1):

• Notes:
  • Use latest editions of referenced standards.
  • Special forms or unusual cases require additional verification by analysis or testing.

flowchart LR
    A[IS 3370 Part 1] --> B[Design & Construction]
    B --> C[IS 11682 (RCC Staging)]
    B --> D[IS 456 (Reinforced Concrete)]
    B --> E[IS 1343 (Prestressed Concrete)]
    B --> F[Special Cases: Analysis/Test]

This ensures safety and durability in liquid retaining RCC structures.

IS 3370 Part 1: Materials - Key Specifications

1. Concrete Mix Requirements (Table 1)

2. Material Standards

• Concrete materials must comply with IS 456 (Reinforced Concrete) and IS 1343 (Prestressed Concrete).
• Cement content should generally not exceed 400 kg/m³ (excluding fly ash/GGBS) to avoid cracking risks.

3. Jointing Materials (Clause 3.2)

• Joint fillers, sealants, and water bars must meet relevant IS standards.
• Polyurethane and silicone sealants are allowed if proven suitable.
• Joint materials must not contaminate the stored liquid.

4. Exposure Conditions (Clause 4)

• Structures in contact with liquid or vapor are considered under 'severe' exposure per IS 456.
• For 'very severe' or 'extreme' exposures, follow IS 456 provisions strictly.

Summary Diagram: Material Selection Flow

flowchart TD
    A[Start: Concrete Type] --> B{Type?}
    B -->|Plain| C[Min Cement 250 kg/m³, W/C 0.50, Grade M20]
    B -->|Reinforced| D[Min Cement 320 kg/m³, W/C 0.45, Grade M30]
    B -->|Prestressed| E[Min Cement 360 kg/m³, W/C 0.40, Grade M40]
    C --> F[Check IS 456]
    D --> F
    E --> F
    F --> G{Exposure Condition}
    G -->|Severe| H[Follow IS 456]
    G -->|Very Severe/Extreme| I[Strictly follow IS 456]

This ensures durability and compliance with IS 3370 Part 1 requirements.

IS 3370 Part 1: Design Requirements - Key Specifications

1. Material Requirements (Clause 3.1)

• Follow IS 456 for reinforced concrete.
• Follow IS 1343 for prestressed concrete.
• Additional requirements specific to water tanks apply.

2. Durability (Clause 6.1)

• Durability provisions ensure watertightness and resistance to chemical attack.
• Minimum cement content and max water-cement ratio are specified to maintain durability.

3. Concrete Mix Requirements (Table 1)

Summary:

• Use M30 or higher for reinforced concrete tanks.
• Maintain water-cement ratio ≤ 0.45 for reinforced concrete to ensure durability.
• Cement content must not be less than specified for watertightness.

flowchart TD
    A[Design Requirements] --> B[Material Standards]
    B --> C[IS 456 - Reinforced Concrete]
    B --> D[IS 1343 - Prestressed Concrete]
    A --> E[Durability Provisions]
    E --> F[Minimum Cement Content]
    E --> G[Max Water-Cement Ratio]
    A --> H[Concrete Grades]
    H --> I[Plain Concrete - M20]
    H --> J[Reinforced Concrete - M30]
    H --> K[Prestressed Concrete - M40]

This ensures structural safety, watertightness, and durability as per IS 3370 Part 1.

IS 3370 Part 1 (2009) - Durability Key Points

1. Concrete Mix Requirements (Table 1)

2. Exposure Conditions

• Parts retaining liquid or enclosing space above liquid are "severe" exposure (per IS 456).
• For very severe/extreme exposure, follow IS 456 provisions strictly.

3. Cement Content Limits

• Cement content (excluding fly ash/GGBS) should not exceed 400 kg/m³ without special design consideration to avoid:
  • Drying shrinkage cracking
  • Early thermal cracking
  • Alkali-silica reaction risks

4. Jointing Materials (Clause 3.2)

• Must comply with relevant IS standards.
• Polyurethane/silicone sealants allowed if proven suitable.
• No adverse effect on stored liquid quality.

Summary:

• Use minimum cement content and max water-cement ratio as per Table 1.
• Follow IS 456 for durability detailing.
• Control cement content to minimize cracking risks.
• Use approved jointing materials ensuring liquid quality.

flowchart LR
    A[Durability Requirements] --> B[Concrete Mix per Table 1]
    A --> C[Exposure Condition: Severe or Higher]
    A --> D[Cement Content ≤ 400 kg/m³]
    A --> E[Approved Jointing Materials]
    B --> F[Min Cement Content & Max W/C Ratio]
    C --> G[IS 456 Provisions]
    D --> H[Control Cracking Risks]
    E --> I[No Adverse Effect on Liquid]

This ensures long-term durability of concrete structures storing liquids.

IS 3370 Part 1: Causes and Control of Cracking

Key Causes of Cracking (Clause 8.1.2)

• Temperature changes: Heat from cement hydration causes expansion; later cooling causes contraction.
• Moisture changes: Loss or gain of moisture causes volume changes.
• Restraints: Internal/external restraints to these dimensional changes cause tensile stresses and cracking.

Control Measures (Clause 8.2.4 & 8.2.8)

• Reduce temperature/moisture gradients: Use proper shuttering, gradual deshuttering, and curing for minimum 14 days.
• Reinforcement: Provide adequate reinforcement to control crack width and distribution.
• Movement joints: Include joints to accommodate expansion/contraction.
• Strengthening: When cracks or tension overstressing are unavoidable, strengthen sections using IS 456 coefficient of thermal expansion.

Thermal Expansion Coefficient (from IS 456)

Summary Formula for Thermal Stress:

[ \sigma = E \times \alpha \times \Delta T ]

• ( \sigma ) = thermal stress
• ( E ) = modulus of elasticity of concrete
• ( \alpha ) = coefficient of thermal expansion
• ( \Delta T ) = temperature change

flowchart LR
    A[Temperature & Moisture Change] --> B[Dimensional Changes]
    B --> C[Restraint by Reinforcement/Structure]
    C --> D[Internal Stresses]
    D --> E[Cracking]
    E --> F[Control Measures]
    F --> G[Proper Curing & Shuttering]
    F --> H[Reinforcement Design]
    F --> I[Movement Joints]
    F --> J[Strengthening Sections]

Note: Always consider site-specific factors like soil pressure, floatation, and foundation movement (Clause 7.2) to prevent structural distress leading to cracking.

IS 3370 Part 1: Site Selection & Foundation Considerations

Key Factors (Clause 7.1 & 7.2)

• Soil Characteristics: Physical, chemical, geological properties influence design.
• Floatation Risk: Check uplift and stability due to water-logged ground.
• Earth Pressure: Account for adverse soil pressure on walls; no credit for beneficial pressure when full.
• Stability: Check against sliding and overturning, especially on slopes.
• Settlement/Subsidence: Consider geological faults, mining, earthquakes—use joints for movement.
• Injurious Soils: Chemical analysis essential; follow IS 456 for sulphate attack protection.

Floatation Design (7.2b)

• Factor of Safety (FoS) against uplift: 1.2
• Design walls/floor to resist uplift stresses.
• Provide drainage to lower external water table.
• Use relief valves if contamination is not a concern.
• Design both faces as water-retaining if submerged.
• Consider sudden groundwater changes.

Stability Checks (per IS 456)

• Overturning: Moment of resisting forces > Moment of overturning forces.
• Sliding: Frictional resistance + passive earth pressure > horizontal forces.

Typical Uplift Stability Formula:

[ \text{FoS} = \frac{\text{Weight of structure} + \text{Downward soil pressure}}{\text{Upward hydrostatic pressure}} \geq 1.2 ]

Summary Table: Site Considerations

flowchart TD
    A[Site Selection] --> B[Soil Physical & Chemical Tests]
    B --> C{Water-Logged?}
    C -- Yes --> D[Design for Floatation]
    C -- No --> E[Standard Foundation Design]
    D --> F[Uplift Stability Check (FoS ≥ 1

IS 3370 Part 1: Joints in Concrete Structures - Key Points

1. Types of Joints (Clause 10.1)

• Movement Joints: Allow relative movement; maintain water tightness.

  • Contraction Joints: No initial gap; accommodate contraction.
    • Complete: Both concrete & steel interrupted.
    • Partial: Concrete interrupted, steel continuous.
  • Expansion Joints: Initial gap; accommodate expansion/contraction; both steel & concrete interrupted.
  • Sliding Joints: Allow sliding with minimal restraint; both steel & concrete interrupted.

• Construction Joints: For construction convenience; full structural continuity expected; surface roughened for bond.

• Temporary Open Joints: Initially left open, later filled with concrete or jointing materials.

2. Design & Detailing of Movement Joints (Clause 10.2)

• Must accommodate repeated movement without water tightness loss.
• Prevent grit/debris entry.
• Joint materials must:
  • Resist permanent distortion, extrusion.
  • Not slump in heat or become brittle in cold.
  • Be insoluble, durable, non-toxic if required.
• Avoid reinforcement congestion; use careful steel selection and bundling.

3. Jointing Materials (Clause 3.2)

• Use IS-approved joint fillers, sealing compounds, water bars.
• Polyurethane/silicone sealants allowed if proven suitable.
• Materials must not contaminate stored liquid.

4. Construction Joints (Clause 10.4.1)

• Minimize number of joints.
• Place at accessible locations.
• Clean laitance/cement slurry immediately after initial setting.
• Roughen surface for bond (wire brushing, sand blasting).
• Keep surface damp for 6+ hours before new concrete placement.

Typical Joint Details (from figures in IS 3370 Part 1):

IS 3370 Part 1: Jointing Materials Key Points

1. Classification (Clause 10.5):

• Joint fillers
• Water bars
• Joint sealing compounds (including primers)

2. Properties of Joint Materials (Clause 10.2):

• Accommodate repeated movement without losing water tightness.
• Exclude grit/debris to allow joint closure.
• Should not distort, extrude, slump (hot), or become brittle (cold).
• Insoluble, durable, unaffected by light or evaporation.
• Non-toxic or chemically resistant if specified.

3. Joint Sealing Compounds (Clause 10.5.3):

• Based on asphalt, bitumen, or coal tar pitch + fillers (limestone, slate dust, asbestos fiber, hemp, rubber).
• Applied hot/cold by pouring, trowelling, gunning, or strips.
• Primer recommended for adhesion; surface drying advised.
• Used in floor joints (in chases) or expansion joints (with joint filler below).
• Chase dimensions must allow complete filling and maintain water path length.
• Cover slabs (Fig. 6E) can reduce tension on sealing compound.

4. Standards Compliance (Clause 3.2):

• Materials must conform to relevant IS standards.
• Polyurethane/silicone sealants allowed if proven suitable.
• No adverse effect on stored liquid quality.

Typical Chase Dimensions for Floor Joints (Indicative)

Design Considerations Summary

flowchart TD
    A[Movement Joint] --> B[Joint Filler]
    A --> C[Water Bar]
    A --> D[Sealing Compound]
    D --> E[Primer for Adhesion]
    D --> F[Applied Hot/Cold]
    B --> G[Prevents Concrete Contact]
    C --> H[Stops Water Penetration]
    E --> I[Improves Adhesion]

References:

• IS 3370 Part 1: Clauses 10.2, 10.5, 10.5.3, 3.2
• IS 456 for exposure conditions and concrete requirements

IS 3370 Part 1: Construction Key Points

1. Durability Requirements (Clause 6.1 & Table 1)

• Minimum Cement Content, Max Water-Cement Ratio & Concrete Grade:

2. General Construction Guidelines

• Common methods of design and construction are covered.
• For special forms or unusual conditions, special design and construction methods may be used with adequate proof of safety (analysis or tests).

3. Wall Construction (Clause 11.4)

• Specific provisions for construction of walls are detailed in Clause 11.4 (refer IS 3370 Part 2 for reinforced concrete structures).

Summary:

• Use minimum cement content and maximum water-cement ratio as per Table 1 to ensure durability.
• Follow standard construction practices unless special designs are justified.
• Refer to Part 2 for reinforced concrete wall construction details.

flowchart TD
    A[Start Construction] --> B{Concrete Type}
    B -->|Plain| C[Min Cement 250 kg/m³]
    B -->|Reinforced| D[Min Cement 320 kg/m³]
    B -->|Prestressed| E[Min Cement 360 kg/m³]
    C --> F[Max W/C 0.50, Grade M20]
    D --> G[Max W/C 0.45, Grade M30]
    E --> H[Max W/C 0.40, Grade M40]
    F & G & H --> I[Ensure Durability & Safety]
    I --> J[Proceed with Construction]

For detailed reinforcement and structural design, refer to IS 3370 Part 2 and related literature.

IS 3370 Part 1 does not explicitly detail testing procedures for concrete liquid retaining structures. Instead, it refers to:

• IS 456 (Plain and Reinforced Concrete Code) and
• IS 1343 (Prestressed Concrete Code)

for construction and testing norms of reinforced and prestressed concrete structures respectively.

Key Points on Testing from Related Codes:

• IS 456:

  • Concrete cube tests for compressive strength (usually 7 and 28 days).
  • Slump test for workability.
  • Non-destructive tests (rebound hammer, ultrasonic pulse velocity) for quality assessment.
  • Load testing for structural elements if required.

• IS 1343:

  • Prestressing force measurement and losses.
  • Proof load tests on prestressing tendons.
  • Deflection and crack width monitoring during testing.

General Recommendations for Testing Liquid Retaining Structures:

• Water tightness tests: Filling the tank and monitoring leakage.
• Load tests: Applying design loads and monitoring deflections and cracks.
• Leakage criteria: As per IS 3370 Part 2 & 4 for permissible leakage rates.

Summary Table: Testing Essentials

flowchart TD
    A[Design & Construction] --> B[IS 3370 Part 1]
    B --> C{Special Structures?}
    C -- Yes --> D[Special Analysis or Testing]
    C -- No --> E[Refer IS 456 & IS 1343]
    E --> F[Testing per IS 456 & IS 1343]
    F --> G[Concrete Strength & Workability]
    F --> H[Prestress Force & Losses]
    F --> I[Load & Water Tightness Tests]

In brief: For testing of liquid

Lightning Protection for Liquid Retaining Structures (IS 3370 Part 1)

• Clause 13 of IS 3370 Part 1 states:
  "The liquid retaining structures shall be protected against lightning in accordance with IS 2309."

• Key Reference:

  • IS 2309:1989 — Code of practice for the protection of buildings and allied structures against lightning.

Summary of Lightning Protection Requirements (per IS 2309):

• Air Terminals (Lightning Rods): Installed at highest points of the structure.
• Down Conductors: Low resistance path to earth, minimum cross-section as per IS 2309.
• Earth Electrodes: Proper earthing system with earth resistance typically less than 10 Ω.
• Bonding: Metallic parts and reinforcement should be bonded to the lightning protection system.
• Minimum Ventilation: Ensure ventilation openings as required for safety and structural integrity.

Typical Lightning Protection Design Formulae (from IS 2309):

Testing & Inspection (per IS 3370 Clause 12.1.3):

• Roof water-tightness test to ensure no leakage before lightning protection installation.
• Continuous water application or flooding to check for leaks.

graph TD
    A[Air Terminal] --> B[Down Conductor]
    B --> C[Earth Electrode]
    C --> D[Earth]
    A -. Bonding .-> E[Reinforcement]

In brief: IS 3370 Part 1 mandates lightning protection per IS 2309, focusing on proper air terminals, down conductors, earthing, and bonding to ensure safety of liquid retaining structures.

IS 3370 Part 1: Annexes & Committee Composition Summary

Annex A: List of Referenced Indian Standards

• These standards are integral references and should be used in conjunction with IS 3370 Part 1.

Annex B: Committee Composition Highlights

• Chairman: Shri Jose Kumian
• Member Organizations:
  • Central Public Works Department, New Delhi
  • Central Water Commission, New Delhi
  • Indian Institute of Technology, Roorkee
  • Cement Manufacturers' Association, Noida
  • Indian Concrete Institute, Chennai
  • Nuclear Power Corporation of India Ltd., Mumbai
  • Military Engineer Services, New Delhi
  • Various cement companies and research institutes
• Secretariat: Bureau of Indian Standards (BIS) with key scientists and engineers.

Key Specifications:

• Roof water-tightness test: Flood roof with ≥25 mm water for 24 h or continuous water flow for ≥6 h.
• Lightning protection per IS 2309.
• Ventilation requirements must be ensured.

This committee and annex list ensure the standard reflects comprehensive expertise and cross-disciplinary inputs for safe, durable liquid-retaining concrete structures.

flowchart LR
  A[IS 3370 Part 1] --> B[Annex A: Referenced IS Codes]
  A --> C[Annex B: Committee Composition]
  B --> D[IS 456 - Concrete Code]
  B --> E[IS 2309 - Lightning Protection]
  B --> F[IS 3370 Part 2 - RCC Structures]
  C -->