Code of Practice for General Construction of Plain and Reinforced Concrete for Dams and Other Massive Structures

IS 457: Foreword - Key Points & Specifications

• Purpose: IS 457 primarily sets requirements for the quality and use of concrete materials. It does not cover all contractual provisions.

• References: All Indian Standards cited (except IS 460-1953) refer to their latest versions.

• Units: Metric system is adopted; foot-pound units are being phased out.

• Rounding Off: Final test or calculation values must be rounded per IS 2-1949 rules, matching decimal places of specified values.

• Scope: Emphasizes quality control of materials, concrete mix, placing, curing, and testing.

Important Notes from Foreword:

Rounding Off Rule (IS 2-1949):

• If specified value = 25.0, round off to 1 decimal place.
• Example: 24.96 → 25.0; 24.94 → 24.9

Summary Diagram of IS 457 Structure

graph TD
  A[IS 457] --> B[Materials]
  A --> C[Concrete]
  A --> D[Forms]
  A --> E[Construction Joints]
  A --> F[Tests]
  B --> B1[Cement]
  B --> B2[Aggregates]
  B --> B3[Water]
  C --> C1[Mix Proportions]
  C --> C2[Workability]
  C --> C3[Placing & Curing]
  F --> F1[Field Tests]
  F --> F2[Lab Tests]

This foreword sets the foundation for quality assurance in concrete works per IS 457. For detailed formulas and tables, refer to respective clauses on mix proportions, slump, and testing.

IS 457 - Scope Summary

• Scope (Clause 1): IS 457 covers specifications for plain and reinforced concrete used in general construction, including materials, mix design, placing, compaction, curing, and testing.

• It applies to:

  • Cement, admixtures, water, aggregates, and reinforcement materials.
  • Concrete production: mixing, handling, conveying, placing, compacting, and curing.
  • Formwork design, erection, and removal.
  • Construction joints and their treatment.
  • Quality control through field and laboratory tests.

Key Specifications from IS 457 Scope:

Typical Concrete Mix Proportion Formula (IS 456 aligned):

[ \text{Mix Ratio} = \frac{Cement : Fine Aggregate : Coarse Aggregate}{Water/Cement ; ratio} ]

• Example: 1 : 2 : 4 (for M15 concrete)
• Water/Cement ratio typically ranges 0.4 to 0.6 depending on strength and workability.

flowchart LR
    Materials --> ConcreteMix
    ConcreteMix --> Placing
    Placing --> Compaction
    Compaction --> Curing
    Curing --> Testing
    Testing --> QualityControl

Summary: IS 457 defines the comprehensive framework for concrete materials, production, placing, curing, and testing ensuring durable and quality concrete structures.

IS 457 - Materials: Key Specifications & Formulas

1. Materials (Clause 3)

• Cement (3.1): Use OPC conforming to IS 269.
• Admixtures (3.2): Should comply with IS 9103.
• Water (3.3): Clean, free from harmful impurities.
• Aggregates (3.4):
  • Coarse and fine aggregates as per IS 383.
  • Size and grading important for workability & strength.
• Reinforcement (3.5): Conforming to IS 1786.

2. Measurement of Materials (Clause 4.6)

• Materials must be measured by weight or volume accurately.

• Typical mix proportioning: (Example for nominal mix)

  Mix Grade	Cement (kg)	Sand (kg)	Coarse Aggregate (kg)	Water (lit)
  M20	1	1.5	3	0.5

• Water-cement ratio crucial for strength & durability.

3. Concrete Mix Proportions (Clause 4.3)

• Use IS 10262 for detailed mix design.
• Workability controlled by slump (Clause 4.5): Typical slump = 75-100 mm.

Summary Table: Materials Specification

flowchart TD
    A[Materials] --> B[Cement (IS 269)]
    A --> C[Admixtures (IS 9103)]
    A --> D[Water (Clean, IS 456)]
    A --> E[Aggregates (IS 383)]
    A --> F[Reinforcement (IS 1786)]
    G[Measurement]

IS 457 - Mix Proportions: Key Points & Formulas

1. Determination of Mix Proportions (Clause 4.3, 4.2.1)

• Proportions of cement, water, aggregates are based on preliminary lab tests (Appendix B of IS 456-1957).
• Establish a water-cement ratio vs compressive strength curve at 28 days (or earlier full load age).
• Curve points: At least 4 points, each an average of 3 specimens.
• Adopt water-cement ratio corresponding to 1.5 times the required strength on the curve.
• Water-cement ratio must be strictly adhered to for each concrete class.

2. Conversion of Weight to Volume (Clause 4.6.2.1)

• When weigh batchers unavailable, convert weight proportions to volume using site-specific coefficients.
• Coefficients must be determined each time aggregates come from a new source.

3. Mix Proportioning Procedure Summary

Typical Water-Cement Ratio vs Strength Relation (Conceptual)

Important Notes:

• Water-cement ratio controls strength and durability.
• Field adjustments must be approved by engineer-in-charge.
• Sequence and rate of pouring must be controlled for quality.

flowchart TD
    A[Preliminary Lab Tests] --> B[Water-Cement Ratio vs Strength Curve]
    B --> C[Select Water-Cement Ratio for 1.5× Strength]
    C --> D[Calculate Cement Content]
    D

IS 457: Key Concrete Construction Practices

1. Materials Measurement (Clause 4.5)

• Accurate measurement of cement, aggregates, water, and admixtures is vital.
• Use weight batching for precision.
• Water-cement ratio controls strength and durability.

2. Mixing (Clause 4.7)

• Mix concrete uniformly for homogeneity.
• Typical mixing time: 1.5 to 3 minutes in mechanical mixers.
• Hand mixing only for small volumes.

3. Placing & Handling (Clauses 4.8-4.10)

• Avoid segregation and loss of materials.
• Place concrete as close as possible to final position.
• Use chutes, buckets, or pumps for conveying.

4. Compaction (Clause 4.11)

• Use mechanical vibrators to remove air voids.
• Proper compaction improves strength and durability.

5. Curing & Protection (Clause 4.14)

• Maintain moisture for at least 7 days (28 days for high strength).
• Methods: Water curing, wet coverings, curing compounds.

6. Formwork (Clause 5)

• Must be rigid, leak-proof, and easy to remove.
• Removal time depends on concrete strength (see Clause 5.5).

Essential Tables (from IS 457)

Quick Formulas

• Water-Cement Ratio (w/c):
  [ w/c = \frac{\text{Weight of Water}}{\text{Weight of Cement}} ]

• Slump Test (Workability):
  Slump = Height of mold - Height of concrete after lifting mold

flowchart TD
    A[Materials Measurement] --> B[Mixing]
    B --> C[Transport & Placing]
    C --> D[Compaction]
    D --> E[Curing

IS 457 - Forms for Concrete: Key Points

1. General Requirements (Clause 5.1)

• Forms must confine and shape concrete as required.
• Use forms for all exposed concrete with slopes ≥ 1:1 unless natural material is trimmed accurately.
• Forms must have sufficient strength and rigidity to resist concrete pressure, vibration, and ramming without excessive deflection.
• Surfaces in contact with concrete must be clean, rigid, tight, and smooth.
• Use devices to maintain accurate alignment at corners and joints.

2. Form Material & Strength

• Forms can be made of timber, steel, or other materials with adequate stiffness.
• Must withstand lateral pressure from fresh concrete, which can be estimated by:

[ p = \gamma_c \times h \times K ]

Where:

• (p) = lateral pressure (kN/m²)
• (\gamma_c) = unit weight of concrete (~24 kN/m³)
• (h) = depth of concrete pour (m)
• (K) = lateral pressure coefficient (usually 0.5 to 1.0 depending on concrete setting time and vibration)

3. Form Ties & Linings (Clauses 5.2 & 5.3)

• Use form ties to hold forms and resist pressure.
• Absorptive form lining may be used to improve surface finish and reduce water loss.

4. Erection and Removal (Clauses 5.4 & 5.5)

• Erect forms to maintain shape and alignment.
• Remove forms only after concrete attains sufficient strength to avoid damage.

Summary Table: Typical Form Pressure (for guidance)

flowchart LR
    A[Concrete Placement] --> B[Forms]
    B --> C{Form Requirements}
    C --> D[Strength & Rigidity]
    C --> E[Clean & Smooth Surface]
    C --> F[Accurate Alignment]
    B --> G[

IS 457: Construction Joints Key Points

1. Horizontal Construction Joints (Clause 6.2, 6.4.1)

• Cleaning & Bonding: Follow Clause 4.10.5 for cleaning masonry joints and bonding new concrete to old.
• Shear Resistance: Use keyways or dowels as per drawings.
• Time Interval: Minimum 2 hours wait after concrete in columns/supporting walls before floor concrete placement.
• Surface Finish: Joints must have a sharp, level, straight exposed face.
• Water Pressure Joints: Control concrete consistency to avoid sand streaking; no free water after compaction.
• Curing: Cure as per Clause 4.15 and protect from mechanical injury.
• Preparation: Clean joints before next lift as per 4.10.5.

2. Emergency Joints (Clause 6.5)

• If concreting is interrupted until final set, form and finish the working face to ensure bond quality equal to regular joints.

3. Form Removal (Clause 5.5.1)

• Remove forms only when concrete strength prevents damage.
• Remove all forms from a lift before starting next lift to allow inspection.
• No heavy loads until design strength is achieved.

Summary Table for Construction Joints

flowchart TD
    A[Place Concrete in Column] -->|Wait 2 hours| B[Place Floor Concrete]
    B --> C[Form Horizontal Joint]
    C --> D[Clean Joint (Clause 4.10.5)]
    D --> E[Place Next Lift Concrete]
    E --> F[Cure Joint (Clause 4.15)]
    F --> G[Inspect & Remove Forms (Clause 5.5.1)]

This ensures durable, well-bonded construction joints resistant to shear and water pressure.

IS 457: Testing and Quality Control - Key Points

1. Testing Requirements (Clause 7)

• Field Tests (7.1): Conduct slump, temperature, and air content tests on fresh concrete.
• Laboratory Tests (7.2):
  • On-site lab with equipment for physical tests.
  • Compression testing machine capacity ≥ 100 metric tonnes.
  • Uniform load application rate mandatory.
• Test Records (7.3): Maintain detailed records of all tests.
• Test Pieces (7.4): Standard specimen sizes for compression and flexure tests.
• Compression Tests (7.5): Use standard cubes/cylinders, tested at 7, 14, 28 days.
• Flexure Tests (7.6): Use simple beam with third-point loading (Appendix C).

2. Consistency Determination (Appendix A)

• Use Vee-Bee Consistometer for concrete workability consistency.

3. Specimen Handling (Appendix B)

• Guidelines for securing hardened concrete specimens from the structure for testing.

Important Formulas & Tables

Compression Strength Calculation:

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

Where:

• ( f_c ) = compressive strength (N/mm²)
• ( P ) = maximum load (N)
• ( A ) = cross-sectional area (mm²)

Summary Diagram of Testing Workflow

flowchart TD
    A[Concrete Sampling] --> B[Field Tests: Slump, Temp, Air]
    B --> C[Specimen Preparation]
    C --> D[Laboratory Tests: Compression, Flexure]
    D --> E[Test Results Recording]
    E --> F{Meets Requirements?}
    F -- Yes --> G[Use Concrete]
    F -- No --> H[Review Mix

IS 457: Finishes for Concrete Surfaces (Clause 4.16.1 & 4.16.2)

Formed Surface Finishes

Unformed Surface Finishes

Mortar Mix for Sack Rubbing (F3 Finish)

• Cement : Sand = 1 : 2 (by volume)
• Sand passing IS Sieve 100
• Consistency: Thick cream
• Application: Wet surface → apply mortar → rub with burlap → dry mortar dust → final burlap rub → fog spray → moist cure 72h+

flowchart TD
    A[Formed Surfaces] -->|

IS 457 - Clause 4.15: Repair of Concrete

Key Specifications and Procedures:

• Timing: Repairs should be done as soon as possible, ideally within 24 hours after form removal.
• Surface Defects:
  • Remove damaged, honeycombed, fractured, or defective concrete.
  • Excavate and rebuild surface depressions with dry-patching mortar.
• Protrusions: For finishes F2 and F3, reduce bulges by bush-hammering and grinding to bring surface within limits.
• Drypack Filling:
  • Used for holes where one dimension ≤ hole depth.
  • Suitable for tie rod fastener holes, grout pipe recesses, narrow crack repairs.
  • Not required for F1 finish surfaces at tie rod holes.
• Dry-patching Mortar Mix:
  • Cement : Sand = 1 : 2 by volume
  • Just enough water to hold mix.
  • Place in layers of 2.5 cm (1 inch), tamp thoroughly.
  • Final layer smoothened to match surface.

Dry-patching Mortar Layer Placement

flowchart TD
    A[Remove defective concrete] --> B[Prepare dry-patching mortar (1:2 cement:sand)]
    B --> C[Place mortar in 2.5 cm layers]
    C --> D[Tamp each layer thoroughly]
    D --> E[Final layer smoothened]
    E --> F[Surface conforms to required finish]

This ensures durable, visually acceptable repairs conforming to IS 457 standards.

IS 457: Depositing Concrete Under Water (Clause 4.12)

Key Specifications & Methods

• General:
  • Concrete should not be deposited underwater if the area can be dewatered.
  • Approval of method, equipment, mix by engineer is mandatory.
  • No placing in running water.
  • Cofferdams/forms must reduce water velocity < 0.3 m³/min (or 10 ft³/min).
  • No pumping/bailing during and 24 hrs after placing.

Methods of Depositing Concrete Under Water (Clause 4.12.2)

Important Notes on Tremie Method

• Tremie pipe must be strong enough to withstand water pressure and possible vacuum.
• Keep lower end submerged in plastic concrete to avoid laitance.
• If charge lost, raise tremie above surface, re-plug, refill before resuming.

flowchart TD
    A[Start Concrete Placement] --> B{Is dewatering possible?}
    B -- Yes --> C[Place concrete in dry condition]
    B -- No --> D[Select underwater method]
    D --> E{Method}
    E --> F[Tremie]
    E --> G[Drop Bottom Bucket]
    E --> H[Bags]
    F --> I[Pipe ≥ 20cm dia, continuous flow, submerged tip]
    G --> J[Fill bucket, lower slowly, dump on surface]
    H --> K[Fill bags 2/3, tie, place interlocked]

This ensures quality concrete placement underwater avoiding segregation, washout, and weak layers.

IS 457 - Handling and Conveying Concrete: Key Points

1. Handling and Conveying (Clause 4.8)

• Concrete must be transported maintaining uniform flow without segregation or piling, especially on steep inclines or transfer points.
• Use covered conveyors (belt conveyors) to protect concrete from:
  • Rain
  • Heat loss in cold weather
  • Evaporation or overheating by sun
  • Other deterioration

2. Belt Conveyors (Clause 4.8.2.4)

• Concrete discharge shall not be directly into forms unless the conveyor end can be moved to place concrete evenly.
• Otherwise, use hoppers, buckets, short chutes, or spouts for controlled placing.

3. Preparation for Placing Concrete (Clause 4.9)

• Ensure proper access and equipment to avoid segregation.
• Maintain concrete temperature and workability during handling.

Practical Tips & Specifications:

Summary Diagram (Concrete Handling Flow):

flowchart LR
    A[Mixing Plant] --> B[Transport to Site]
    B --> C{Conveyor Type?}
    C -->|Belt Conveyor| D[Covered Conveyor]
    C -->|Others| E[Direct Transport]
    D --> F{Discharge Method?}
    F -->|Movable End| G[Direct Discharge in Form]
    F -->|Fixed End| H[Use Hopper + Chute]
    G & H --> I[Even Layer Placement]
    I --> J[Compaction & Curing]

Note: For detailed mix proportions, slump limits, and curing, refer to respective clauses 4.3, 4.5, and 4.14 in IS 457.

Curing of Concrete (IS 457: Clause 4.14)

Key Specifications:

• Duration: Concrete must be kept continuously moist for at least 14 days after placement.
• Protection: Exposed surfaces must be protected against drying and heating by sun for minimum 72 hours.
• Construction Joints: Kept moist for at least 72 hours before placing additional concrete.
• Methods for Horizontal Surfaces:
  • Sprinkling water
  • Covering with damp sand or wet sacks (remove covers later)
• Water Curing: Mandatory in dams, using sprays or sprinklers for full coverage.
• Formwork: Keep sprinkled until removal.
• Disturbance: No walking or material storage on concrete for at least 10 hours after placement.

Additional Notes on Temperature Control (Clause 4.10.4)

• Concrete temperature on placement should not exceed limits from cooling studies.
• Cooling methods include:
  • Spraying aggregates with water/air blasting
  • Refrigerated mixing water
  • Cooling towers
  • Placing during cooler hours
• Maximum lift thickness on rock foundation: 75 cm (2.5 ft)

Summary Table for Curing Duration

flowchart TD
    A[Concrete Placement] --> B{Protect from Sun Heat?}
    B -- Yes --> C[Protect for 72 Hours]
    B -- No --> D[Start Moist Curing]
    D --> E[Keep Continuous Moisture for 14 Days]
    E --> F[No Disturbance for 10 Hours]
    F --> G[Remove Covers After Curing]

Remember: Proper curing ensures strength, durability, and crack resistance of concrete.

IS 457: Sampling and Test Specimens - Key Points

1. Specimen Size and Moulding (Clause 7.6 & Appendix C)

• Flexure test specimens: Use simple beams with third-point loading as per Appendix C.
• Dimensions typically: 100 mm x 100 mm x 500 mm beams.
• Moulding and curing must follow standard procedures to ensure uniformity.

2. Test Specimen Measurements (Clause 5.1)

• Measure width & depth at failure section to nearest 0.25 cm.
• Calculate average dimensions for stress computations.

3. Consistency of Concrete (Clause 4.2.1 & Table II)

• Use Vee-Bee Consistometer to determine workability.
• Vee-Bee degrees and corresponding consistency:

4. Securing Hardened Specimens (Appendix B)

• Specimens must be carefully extracted from structure to avoid damage.
• Use appropriate supports and curing after extraction.

Flexure Test Setup (Appendix C)

flowchart LR
    A[Concrete Beam Specimen] --> B[Simple Beam Support]
    B --> C[Third-Point Loading]
    C --> D[Measure Deflection & Failure Load]

Summary:

• Follow Appendix C for flexure specimen size and testing.
• Measure specimens precisely (±0.25 cm).
• Use Vee-Bee degrees for workability classification.
• Handle specimens carefully per Appendix B to maintain integrity.

This ensures reliable sampling and testing consistent with IS 457 standards.

IS 457 Appendices: Key Formulas, Tables & Specifications

Appendix A: Consistency of Concrete by Vee-Bee Consistometer

• Measures workability in Vee-Bee degrees.
• Consistency Scale (Table II):

Appendix B: Securing Hardened Concrete Specimens

• Guidelines for extracting and securing concrete samples from structures for testing.
• Ensures specimen integrity for compressive and flexural strength tests.

Appendix C: Flexural Strength of Concrete

• Test: Simple beam with third-point loading.
• Formula for flexural strength ( f_r ):

[ f_r = \frac{PL}{bd^2} ]

Where:

• ( P ) = Load at failure (N)
• ( L ) = Span length (mm)
• ( b ) = Width of beam (mm)
• ( d ) = Depth of beam (mm)

Additional Important Table: Compressive Strength Correction (Clause 6.5)

Summary Diagram: Concrete Strength Testing Flow

flowchart TD
    A[Concrete Sample] --> B[Specimen Preparation]
    B --> C{Test Type}
    C -->|Compression| D[Compression