Code of practice Concrete structures for the storage of liquids, Part 1: General requirements
2009 Edition

Scope Overview:

• Addresses design and construction of concrete tanks for water storage.
• Excludes dams, pipelines, lined structures, and basement damp-proofing.

Concrete Specifications (Clause 5(a), Foreword):

Durability (Clause 6.1):

• Concrete mix must ensure long-term durability.
• Cement content and water-cement ratio limits are critical to resist water ingress and chemical attack.

Summary:

• Reinforced concrete tanks should use at least M30 grade with water-cement ratio ≤ 0.45 and cement content ≥ 320 kg/m³.

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

Ensures proper structural integrity and service life for water-retaining concrete applications.

Applicable Codes:

• IS 11682: Design criteria for RCC staging in overhead tanks.
• IS 456: General code for plain and reinforced concrete.
• IS 1343: Code for prestressed concrete structures.
• Latest versions to be used unless otherwise specified.

Concrete Quality and Durability Requirements (Table 1):

Remarks:

• Special or atypical situations require additional analysis or testing validation.

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

Supports safe and durable RCC liquid storage structures.

Material Requirements per IS 3370 Part 1:

Concrete Mix Criteria (Table 1):

Material Standards:

• Materials must conform to IS 456 and IS 1343 respectively.
• Cement content generally limited to 400 kg/m³ (excluding supplementary cementitious materials) to mitigate cracking.

Joint Materials (Clause 3.2):

• Joint fillers, sealants, and water bars should comply with relevant IS codes.
• Polyurethane and silicone sealants permitted if demonstrated suitable.
• Joint materials must not contaminate stored liquids.

Exposure Conditions (Clause 4):

• Liquid-contacting surfaces classified as 'severe' exposure under IS 456.
• For 'very severe' or 'extreme' exposures, IS 456 guidelines are strictly followed.

flowchart TD
  A[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 & D & E --> F[Check IS 456 Compliance]
  F --> G{Exposure Severity}
  G -->|Severe| H[Follow IS 456]
  G -->|Very Severe/Extreme| I[Strict IS 456 Adherence]

Ensures durability and compliance with concrete storage standards.

Design Principles (IS 3370 Part 1):

1. Material Standards:

   • Use IS 456 for reinforced concrete design.
   • Use IS 1343 for prestressed concrete design.
   • Additional water tank-specific provisions apply.

2. Durability Provisions:

   • Ensure watertightness and chemical resistance via minimum cement content and maximum water-cement ratios.

3. Concrete Mix Requirements: | Concrete Type | Min Cement Content (kg/m³) | Max Water-Cement Ratio | Min Concrete Grade | |-----------------------|----------------------------|-----------------------|--------------------| | Plain Concrete | 250 | 0.50 | M20 | | Reinforced Concrete | 320 | 0.45 | M30 | | Prestressed Concrete | 360 | 0.40 | M40 |

Summary:

• Reinforced concrete tanks require minimum M30 grade.
• Water-cement ratio for reinforced concrete limited to 0.45.
• Cement content must adhere to minimum values for durability.

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

Ensures safety, durability, and water tightness in storage structures.

Durability Guidelines According to IS 3370 Part 1 (2009):

Concrete Mix Parameters:

Exposure Conditions:

• Surfaces in contact with liquid or vapor are categorized as 'severe' exposure (per IS 456).
• For 'very severe' or 'extreme' exposure, strict adherence to IS 456 is mandated.

Cement Content Limits:

• Cement content excluding fly ash or GGBS should generally not exceed 400 kg/m³ to avoid drying shrinkage, early thermal cracks, and alkali-silica reactions.

Joint Materials:

• Must comply with IS standards.
• Polyurethane and silicone sealants permitted if validated.
• Should not adversely affect the stored liquid.

Summary:

• Minimum cement content and maximum water-cement ratio per Table 1.
• Follow IS 456 durability detailing.
• Control cement level to reduce cracking potential.
• Use approved jointing materials ensuring quality.

flowchart LR
  A[Durability Requirements] --> B[Concrete Mix per Table 1]
  A --> C[Exposure Severity: Severe or Greater]
  A --> D[Cement Content ≤ 400 kg/m³]
  A --> E[Approved Jointing Materials]
  B --> F[Minimum Cement & Max W/C Ratio]
  C --> G[IS 456 Compliance]
  D --> H[Crack Risk Control]
  E --> I[No Liquid Contamination]

Supports longevity of concrete liquid storage structures.

Causes and Mitigation of Cracking (IS 3370 Part 1):

Primary Causes (Clause 8.1.2):

• Thermal fluctuations: Heat from cement hydration induces expansion, followed by contraction upon cooling.
• Moisture variations: Changes in moisture content cause volume changes.
• Restraints: Structural or reinforcement constraints generate tensile stresses leading to cracks.

Control Strategies (Clauses 8.2.4 & 8.2.8):

• Minimize temperature and moisture gradients through proper formwork, gradual removal, and curing for at least 14 days.
• Adequate reinforcement to limit crack width and distribution.
• Incorporate movement joints for thermal expansion and contraction.
• Strengthen sections when unavoidable cracking or tension overstressing occur, using thermal expansion coefficients from IS 456.

Thermal Expansion Coefficients (IS 456):

Thermal Stress Formula: [ \sigma = E \times \alpha \times \Delta T ] Where:

• (\sigma): Thermal stress
• (E): Modulus of elasticity of concrete
• (\alpha): Coefficient of thermal expansion
• (\Delta T): Temperature change

flowchart LR
  A[Temperature & Moisture Changes] --> B[Volume Changes]
  B --> C[Restraint by Reinforcement/Structure]
  C --> D[Internal Tensile Stresses]
  D --> E[Cracking]
  E --> F[Control Measures]
  F --> G[Proper Curing & Formwork]
  F --> H[Reinforcement Design]
  F --> I[Inclusion of Movement Joints]
  F --> J[Structural Strengthening]

Site-specific factors like soil pressure, flotation, and foundation movement must be considered to avoid distress.

Site and Foundation Factors (IS 3370 Part 1):

Key Considerations (Clauses 7.1 & 7.2):

• Soil properties: Physical, chemical, and geological factors influencing design.
• Flotation risk: Evaluate uplift and stability in waterlogged soils.
• Earth pressures: Account for adverse soil pressure on walls; beneficial pressures when full are not credited.
• Stability: Ensure resistance against sliding and overturning, especially on inclined sites.
• Settlement and subsidence: Consider faults, mining, seismic activity; employ joints to accommodate movements.
• Harmful soils: Perform chemical analysis; protect against sulphate attack per IS 456.

Flotation Design (7.2b):

• Factor of safety against uplift ≥ 1.2.
• Design walls and base slabs to withstand uplift forces.
• Provide drainage systems to lower groundwater table.
• Relief valves may be used if contamination risk is minimal.
• Design submerged faces as water-retaining.
• Consider sudden groundwater fluctuations.

Stability Checks (IS 456):

• Overturning: Resisting moments must exceed overturning moments.
• Sliding: Friction plus passive earth pressure must exceed horizontal loads.

Uplift Stability Formula: [ \text{FoS} = \frac{ \text{Weight of Structure} + \text{Downward Soil Pressure} }{ \text{Upward Hydrostatic Pressure} } \geq 1.2 ]

Summary Table:

flowchart TD
  A[Site Selection] --> B[Soil Testing]
  B --> C{Water-Logged?}
  C -- Yes --> D[Flotation Design]
  C -- No --> E[Standard Foundation Design]
  D --> F[Uplift Stability Check (FoS ≥ 1.2)]
  F --> G[Drainage & Relief Valves]

Ensures foundation stability and longevity of storage structures.

Types of Joints (Clause 10.1):

• Movement Joints: Allow relative displacement while maintaining impermeability.

  • Contraction Joints: No initial gap; accommodate shrinkage; steel and concrete continuity varies (complete or partial).
  • Expansion Joints: Include initial gap; accommodate expansion and contraction; both steel and concrete interrupted.
  • Sliding Joints: Permit sliding movement; steel and concrete interrupted.

• Construction Joints: Created for construction sequencing; ensure full structural continuity; surface roughening for bonding.

• Temporary Open Joints: Initially open, later filled with concrete or sealants.

Design and Detailing (Clause 10.2):

• Joints must accommodate cyclic movements without water-tightness loss.
• Prevent intrusion of grit and debris.
• Joint materials should resist permanent deformation, extrusion, thermal effects, and maintain durability.
• Reinforcement congestion near joints should be avoided by proper detailing.

Joint Materials (Clause 3.2):

• Use IS-approved fillers, sealants, and water bars.
• Polyurethane and silicone sealants allowed if suitable.
• Materials must not contaminate stored liquids.

Construction Joints (Clause 10.4.1):

• Minimize joint number.
• Place joints at accessible locations.
• Remove surface laitance promptly.
• Roughen surface by wire brushing or sandblasting.
• Keep surface moist for at least 6 hours before placing fresh concrete.

Typical Joint Details:

Maintains structural integrity and water-tightness.

Classification of Joint Materials (Clause 10.5):

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

Properties (Clause 10.2):

• Facilitate repeated movements without losing impermeability.
• Prevent grit/debris intrusion.
• Resist permanent deformation, extrusion, slumping in heat, and brittleness in cold.
• Insoluble, durable, unaffected by light or evaporation.
• Non-toxic or chemically resistant if specified.

Sealing Compounds (Clause 10.5.3):

• Based on asphalt, bitumen, or coal tar pitch combined with fillers (limestone powder, slate dust, asbestos fiber, hemp, rubber).
• Applied hot or cold via pouring, troweling, gunning, or strips.
• Primers recommended for adhesion; surface drying required.
• Used in floor joints within chases or expansion joints with fillers below.
• Chase dimensions must allow complete filling and maintain adequate water path length.
• Cover slabs may be employed to reduce tension on sealing compound.

Standards Compliance (Clause 3.2):

• Materials must meet relevant IS standards.
• Polyurethane and silicone sealants allowed if proven suitable.
• No contamination of stored liquids.

Typical Chase Dimensions:

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

Ensures durable, watertight joints in concrete structures.

Construction Guidelines (IS 3370 Part 1):

Durability Requirements (Clause 6.1 & Table 1):

General Practices:

• Standard design and construction methods apply.
• Special forms or conditions require additional safety verification through analysis or testing.

Wall Construction (Clause 11.4):

• Detailed provisions for wall construction are provided; refer also to IS 3370 Part 2 for reinforced concrete specifics.

Summary:

• Adhere to minimum cement content and maximum water-cement ratio for durability.
• Employ conventional construction procedures unless special design justified.
• Consult Part 2 for reinforced concrete wall detailing.

flowchart TD
  A[Begin 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]
  I --> J[Proceed with Construction]

Promotes structural integrity and longevity.

Testing Procedures as per IS 3370 Part 1:

• IS 3370 Part 1 refers to IS 456 and IS 1343 for concrete construction and testing protocols.

Key Tests from Related Codes:

• IS 456:
  • Compressive strength tests on concrete cubes (7 and 28 days).
  • Slump test for workability.
  • Non-destructive tests like rebound hammer and ultrasonic pulse velocity.
  • Load testing when necessary.
• IS 1343:
  • Prestressing force measurements and losses.
  • Proof load tests on prestressing cables.
  • Monitoring deflection and crack widths.

Water-Tightness Testing Recommendations:

• Fill tank and allow 7 days for absorption.
• Measure water level after absorption and daily for 7 days.
• For underground covered tanks, max allowable water drop is 20 mm.
• Elevated or exposed tanks: no external leakage or dampness observed.
• If water loss exceeds limits but daily drop decreases, extend test for another 7 days.

Summary Table:

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

Ensures compliance with structural and watertightness standards.

Lightning Protection Requirements (IS 3370 Part 1, Clause 13):

• Protection must comply with IS 2309: Code of practice for lightning protection of buildings and allied structures.

Key Points from IS 2309:

• Air terminals (lightning rods) installed at highest points.
• Down conductors providing low resistance path to earth, minimum cross-sectional area specified.
• Earth electrodes with resistance typically less than 10 ohms.
• Bonding of metallic parts and reinforcement to lightning protection system.
• Adequate ventilation for safety and structural integrity.

Typical Specifications:

Testing and Inspection (Clause 12.1.3):

• Perform roof water-tightness test before installing lightning protection.
• Use continuous water application or flooding to verify no leakage.

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

Ensures safety of liquid storage structures against lightning strikes.

Annex A: Referenced Indian Standards

Annex B: Committee Composition

• Chairperson: Shri Jose Kumian
• Member Organizations Include:
  • Central Public Works Department
  • Central Water Commission
  • Indian Institute of Technology Roorkee
  • Cement Manufacturers' Association
  • Indian Concrete Institute
  • Nuclear Power Corporation of India
  • Military Engineer Services
  • Various cement companies and research institutes
• Secretariat: Bureau of Indian Standards (BIS), comprising expert scientists and engineers.

Additional Specifications:

• Roof water-tightness test requires flooding with ≥ 25 mm water for 24 hours or continuous water flow for ≥ 6 hours.
• Lightning protection per IS 2309.
• Ensure ventilation as per safety and structural requirements.

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

Reflects comprehensive expertise ensuring safety and durability.