Glossary of terms relating to cement concrete, Part 4: Types of Concrete
1972 Edition

Scope Overview for IS 6461 Part 4 (1972)

Scope:
This section addresses the definition and application of wet-mix shotcrete, where all components including water are combined prior to pneumatic delivery through the hose.

Essential Definitions (Clause 2.129)

• Wet-Mix Shotcrete: Concrete mixture fully combined with water before being pneumatically propelled.

Additional Notes:

• Focus on formwork relevant to shotcrete.
• Applicable for structural and repair projects utilizing shotcrete.
• Includes guidelines on materials, mix design, application methods, and quality assurance.

Typical Parameters for Shotcrete (Complementary to IS 6461 Part 4):

Process Flow for Wet-Mix Shotcrete:

flowchart LR
    A[Batching and Mixing] --> B[Pneumatic Delivery Hose]
    B --> C[Nozzle Application]
    C --> D[Concrete Placement]
    D --> E[Compaction and Finishing]

Refer to the complete IS 6461 Part 4 text for detailed design, testing, and application instructions.

IS 6461 Part 4 primarily provides definitions and classifications of concrete types rather than mix design formulas. Key points include:

Definitions for Concrete Types

• Plain Concrete: Concrete without reinforcement.
• Reinforced Concrete: Concrete reinforced with steel bars.
• Prestressed Concrete: Concrete preloaded with internal stresses to resist tensile forces.
• Lightweight Concrete: Made with lightweight aggregates; density below 2000 kg/m³.
• Heavyweight Concrete: Concrete with density exceeding 2600 kg/m³, commonly used for radiation shielding.
• High Strength Concrete: Concrete with compressive strength greater than 40 MPa.
• Mass Concrete: Large volume concrete where temperature control is critical.

Key Specifications

• Water-Cement Ratio: Influences strength and durability.
• Aggregate Size: Maximum size impacts workability and strength.
• Curing Duration: Minimum 7 days for standard concrete.

Basic Mix Proportioning Formula

• Cement : Fine Aggregate : Coarse Aggregate = 1 : x : y where x and y vary based on required strength and workability.

Example Summary Table

For detailed mix calculations, refer to IS 10262 on concrete mix proportioning.

flowchart LR
    A[Concrete Types] --> B[Plain Concrete]
    A --> C[Reinforced Concrete]
    A --> D[Prestressed Concrete]
    A --> E[Lightweight Concrete]
    A --> F[Heavyweight Concrete]
    A --> G[High Strength Concrete]

IS 6461 Part 4 - Air-Blown Mortar (Shotcrete/Gunite) Overview

Definitions (Clauses 2.2, 2.88, 2.111)

• Air-Blown Mortar: Mortar or concrete pneumatically delivered through a hose and sprayed at high velocity.
• Also known as pneumatically applied mortar, sprayed mortar, gunned concrete, or shotcrete.
• Can be applied via dry-mix or wet-mix methods.

Specifications and Guidelines:

• Components: Cement, fine aggregates, water, and admixtures per design requirements.
• Mix Design: Ensures pumpability and cohesion; wet-mix typically has lower slump.
• Nozzle Velocity: High velocity to facilitate compaction and bonding.
• Layer Thickness: Usually between 25 and 50 mm per pass.
• Material Rebound: Typically 10–20%, considered in quantity calculations.

Example Mix Proportions (Dry Mix):

Important Considerations:

• Surface must be clean and roughened for proper adhesion.
• Immediate curing is vital to prevent shrinkage cracks.
• Thickness control through multiple passes with compaction.

Process Flow Diagram:

flowchart TD
    A[Material Batching] --> B[Mixing (Dry or Wet)]
    B --> C[Pneumatic Conveyance]
    C --> D[High-Velocity Projection]
    D --> E[Layer Formation]
    E --> F[Curing and Finishing]

Consult IS 6461 Part 4 for comprehensive mix designs, equipment details, and workmanship standards.

Highlights of Boron Loaded Concrete in IS 6461 Part 4

• Definition (Clause 2.4):
  A type of high-density concrete incorporating boron compounds such as colemanite, boron frits, or boron metal alloys to improve neutron radiation attenuation.

• Function:
  Boron serves as a neutron absorber, essential for radiation shielding in nuclear facilities.

Key Parameters:

Neutron Attenuation Formula:

[ I = I_0 e^{-\Sigma t} ]

Where:

• (I_0): Initial neutron intensity
• (I): Transmitted neutron intensity
• (\Sigma): Macroscopic neutron absorption cross-section (increases with boron content)
• (t): Concrete thickness (cm)

Conceptual Diagram:

flowchart LR
    A[High-Density Concrete] --> B[Boron Additives]
    B --> C[Neutron Absorption]
    C --> D[Reduced Neutron Flux]
    A --> E[Increased Density]
    E --> C

Refer to IS 6461 Part 4 tables and nuclear shielding design literature for detailed mix formulations and thickness requirements.

IS 6461 Part 4 discusses cast-in-place concrete types, properties, and formwork considerations. While specific clauses are not cited, the following summarizes typical standards and practices:

Specifications:

• Concrete Grades: From M20 to M40 or higher per design.
• Workability: Slump values between 75 and 100 mm for standard casting.
• Mix Design: As per IS 10262 guidelines.

Fundamental Formulas:

• Water-Cement Ratio (w/c): [ w/c = \frac{\text{Weight of Water}}{\text{Weight of Cement}} ] Typically ranges from 0.4 to 0.6 to balance durability and strength.

• Density of Concrete: Approximately 2400 kg/m³.

• Compressive Strength (fck): Usually determined at 28 days (e.g., 20 MPa for M20).

Typical Data Table (from IS 456 and IS 10262):

Formwork Requirements (per IS 6461 Part 5 and IS 456):

• Must be rigid, leak-tight, and strong enough to support loads.
• Designed for easy removal without damaging concrete.
• Alignment and dimensional tolerances as specified in IS 456.

flowchart TD
    A[Mix Design] --> B[Batching and Mixing]
    B --> C[Transport and Placement]
    C --> D[Compaction and Finishing]
    D --> E[Curing]

Summary: Adhere to IS 10262 for mix design, IS 456 for strength and formwork standards, maintaining appropriate water-cement ratios for durability.

IS 6461 Part 4 - Prepacked Concrete Overview

Definition (Clause 2.30)

• Prepacked concrete involves initially placing coarse aggregates into the formwork.
• Subsequently, a grout mixture of Portland cement and sand (with possible additives) is injected to fill voids.

Specifications:

• Aggregate grading must allow adequate grout permeability.
• Grout mix ratios typically range from 1:1 to 1:2 cement to sand by volume, with a water-cement ratio around 0.4 to 0.5 to ensure flowability.
• Admixtures may be incorporated to improve flow and reduce segregation.

Typical Properties (Referenced from Part VIII):

Important Notes:

• Proper grout injection pressure is essential to prevent segregation.
• Adequate curing is necessary for grout hydration.
• Ideal for repair applications or areas with congested reinforcement.

flowchart LR
    A[Place Coarse Aggregate] --> B[Inject Cement-Sand Grout]
    B --> C[Grout Fills Voids]
    C --> D[Compacted Prepacked Concrete]

For detailed mix design and application methods, see IS 6461 Part 4 clauses concerning grout composition and injection.

IS 6461 Part 4 - Refractory Concrete Overview

Definitions:

• Refractory Concrete (Clauses 2.33 & 2.97): Concrete composed of calcium aluminate cement and refractory aggregates, designed for service temperatures exceeding 1000°C.
• Refractory Insulating Concrete (Clause 2.98): Variant with reduced thermal conductivity for insulation purposes.
• Castable Refractory (Clause 2.8): A dry mix of calcium aluminate cement and refractory aggregates that forms refractory concrete or mortar when water is added.

Key Specifications:

• Binder: Calcium aluminate cement for high-temperature durability.
• Aggregates: Refractory materials such as alumina, silica, magnesia chosen for thermal stability.
• Temperature Resistance: Typically above 1000°C.
• Thermal Conductivity: Lower values for insulating types to enhance energy efficiency.

Typical Properties:

Mix Considerations:

• Use calcium aluminate cement for hydraulic setting.
• Select aggregate grading to optimize packing and thermal behavior.
• Adjust water content to balance workability and refractory qualities.

flowchart LR
    A[Calcium Aluminate Cement] --> B[Mixing]
    C[Refractory Aggregates] --> B
    B --> D[Refractory Concrete]
    D --> E{Properties}
    E --> F[High Temperature Resistance >1000°C]
    E --> G[Low Thermal Conductivity (for insulating types)]
    E --> H[Mechanical Strength]

Note: IS 6461 Part 4 focuses on terminology and material selection; for detailed design, consult relevant cement and refractory standards.

IS 6461 Part 4 - Reinforced Concrete Overview

• Clause 2.34: Defines reinforced concrete as concrete combined with reinforcement steel designed to act compositely.

Key Design Formulas:

• Ultimate Flexural Moment: [ M_u = 0.87 f_y A_s \left(d - \frac{A_s f_y}{f_{ck} b} \right) ] Where:

  • (M_u): Ultimate moment
  • (f_y): Steel yield strength
  • (A_s): Area of steel reinforcement
  • (d): Effective depth
  • (f_{ck}): Concrete characteristic strength
  • (b): Beam width

• Concrete Stress Limit: [ \sigma_c = 0.446 f_{ck} ]

• Modular Ratio: [ m = \frac{E_s}{E_c} ] Where (E_s) and (E_c) represent moduli of elasticity for steel and concrete respectively.

Typical Parameters:

flowchart LR
    Concrete -->|Composite Action| Reinforced_Concrete
    Steel -->|Composite Action| Reinforced_Concrete
    Reinforced_Concrete -->|Design Calculations| Structural_Element

Summary: The standard highlights the composite behavior of concrete and reinforcement, providing formulas for flexural strength and stress limits. Detailed design can be found in related parts of IS codes.

IS 6461 Part 4 - Transit-Mixed Concrete Summary

• Definition (Clauses 2.39, 2.118, 2.122): Concrete mixed partially or fully within a truck mixer during transportation to site.

• Requirements:

  • Delivered in a plastic state, ready for placing without additional mixing (Clause 2.32).
  • Controlled mixing time and agitation speed to maintain uniformity and prevent segregation.

• Typical Parameters:

  • Mixing Revolutions: 70 to 100 at 12–18 rpm.
  • Agitation Time: Up to 90 minutes at 2–6 rpm to prevent setting.
  • On-site Water Addition: Restricted and accounted for in mix design.

• Quality Control:

  • Slump and temperature tests upon arrival.
  • Strength sampling as per IS 516.

Process Flow:

flowchart LR
    A[Batching Plant] --> B[Truck Mixer: Mixing (70-100 rev @ 12-18 rpm)]
    B --> C[Transport]
    C --> D[Truck Mixer: Agitation (up to 90 min @ 2-6 rpm)]
    D --> E[Site Discharge and Placement]

Refer to IS 456, IS 4926, and IS 6461 Part 4 for detailed mix and testing protocols.

IS 6461 Part 4 (1972) – Gunite (Dry-Mix Shotcrete) Overview

Definitions:

• Gunite (Clause 2.61): Dry-mix shotcrete process where dry cement and aggregate are pneumatically transported, and water is added at the nozzle.
• Dry-Mix Shotcrete (Clause 2.48): Pneumatically conveyed dry mix with water applied at the nozzle.
• Air-Blown Mortar (Clause 2.2): Mortar or concrete sprayed at high velocity pneumatically.

Key Specifications:

• Mix Ratios: Typically cement:sand:aggregate ratios range from 1:2 to 1:3 by volume.
• Water-Cement Ratio: Controlled at nozzle for proper workability and strength.
• Nozzle Pressure: Generally 3.5 to 4.5 bar.
• Layer Thickness: 25–50 mm per pass to minimize rebound and ensure compaction.

Strength Requirement:

Minimum compressive strength (f_{ck}) typically ≥ 20 MPa for structural applications.

Typical Properties Table:

flowchart LR
    Dry_Mix[Dry Cement and Aggregate Mix] -->|Pneumatic Conveyance| Nozzle
    Water[Water] -->|Added at Nozzle| Nozzle
    Nozzle -->|High Velocity Spray| Surface
    Surface -->|Layer Formation| Hardened Shotcrete

Summary: Gunite is defined as dry-mix shotcrete with water added at the nozzle, requiring strict control of water content, pneumatic pressure, and layer application to ensure quality and strength.

IS 6461 Part 4 - Pneumatically Applied Mortar (Shotcrete/Gunite)

Definitions:

• Mortar or concrete pneumatically conveyed through a hose and sprayed at high velocity (Clauses 2.2, 2.88, 2.111).
• Also known as air-blown mortar, sprayed mortar, gunned concrete, shotcrete, or gunite.

Specifications:

• Uses cement mortar or concrete mixes suitable for pneumatic application.
• High-velocity projection ensures dense compaction and excellent bonding.
• The gunning pattern is a conical discharge shape (Clause 2.62).

Typical Mix Ratios (Referencing IS 456 & IS 383):

Key Parameters:

• Nozzle velocity: 30 to 60 m/s for optimum compaction.
• Layer thickness: 25–50 mm per application pass.
• Compressive strength: Should meet design requirements, usually above 20 MPa at 28 days.

Benefits:

• High bond strength due to impact compaction.
• Ideal for repairs and complex geometries.

flowchart LR
    A[Mortar/Concrete Mix] --> B[Hose Conveyance]
    B --> C{High Velocity Spray}
    C --> D[Surface Application]
    D --> E[Compacted Pneumatically Applied Layer]

References: IS 6461 Part 4 (1972), IS 456, IS 383.

For further details on mix design and application, consult the standard and shotcrete guidelines.

IS 6461 Part 4 - Ready-Mixed Concrete Details

• Definition (Clause 2.32): Concrete delivered to site in a plastic state, requiring no additional mixing before placement.

• Types:

  • Transit-Mixed Concrete (Clause 2.118): Mixed during transit in truck mixers.
  • Centrally Mixed Concrete (Clause 2.107): Completely mixed at batching plant, delivered plastic.

• Specifications:

  • Must maintain workability throughout transport.
  • Time constraints on delivery and placement to prevent premature setting.
  • Mix designs adhere to IS 456 and IS 10262 for strength and durability.

• Typical Parameters:

  Parameter	Typical Ranges
  Slump	25–75 mm (adjusted per use)
  Maximum Transit Time	Approximately 90 minutes (temperature dependent)
  Water-Cement Ratio	Between 0.4 and 0.6
  Compressive Strength	Per IS 456 design (e.g., M20, M25)

• Additional Notes:

  • Use admixtures to maintain slump if necessary.
  • Continuous agitation during transport avoids segregation.

flowchart LR
    A[Batching Plant] --> B[Concrete Mixing]
    B --> C[Transport via Transit Mixer]
    C --> D[Site Delivery]
    D --> E[Placing and Compaction]
    E --> F[Setting and Hardening]

Summary: Ready-mixed concrete per IS 6461 Part 4 is fresh, plastic concrete delivered with controlled mix and transport to ensure site quality.

IS 6461 Part 4 - Tremie Concrete and Seal Definitions

Definitions:

• Tremie Concrete (Clause 2.120): Concrete placed underwater using a tremie pipe to prevent segregation.
• Tremie Seal (Clause 2.121): Concrete placed underwater inside cofferdams or caissons by tremie method, subsequently dewatered after curing.

Specifications:

• Low slump concrete (50 to 75 mm) to facilitate pumpability.
• Well-graded aggregates to minimize segregation.
• Use of admixtures to control workability and setting time.

Placement Instructions:

• Keep tremie pipe bottom submerged within fresh concrete to avoid water contamination.
• Maintain a continuous pour to prevent cold joints.

Typical Properties:

Volume Calculation:

[ V = A \times h ]

Where:

• (V): Concrete volume (m³)
• (A): Cross-sectional area of cofferdam/caisson (m²)
• (h): Height of pour (m)

Placement Process Flow:

flowchart TD
    A[Initiate Tremie Placement] --> B[Insert Tremie Pipe]
    B --> C[Maintain Pipe Submerged]
    C --> D[Continuous Concrete Pour]
    D --> E[Concrete Hardening]
    E --> F[Dewatering]
    F --> G[Inspect Tremie Seal]

Summary: Use low-slump, well-graded concrete placed underwater continuously through a tremie pipe to create an effective tremie seal. Proper pipe submersion and segregation prevention are critical.

IS 6461 Part 4 - Vermiculite Concrete Overview

• Definition (Clause 2.127): Concrete incorporating exfoliated vermiculite as an aggregate.
• Categorized under lightweight concrete (Clause 2.72).
• Density ranges from approximately 400 to 1200 kg/m³ depending on mix.
• Thermal conductivity typically between 0.07 and 0.20 W/m·K, providing excellent insulation.
• Compressive strength varies from 1 to 10 MPa.
• High water absorption due to vermiculite’s porous nature; controlled curing is critical.

Typical Mix Proportions (by volume):

Notes:

• Primarily used for non-structural or lightly loaded insulation applications.
• Employed in thermal insulation, fire protection, and lightweight fills.
• Requires carefully controlled mixing and curing to minimize shrinkage and cracking.

flowchart LR
    Cement --> Mix
    Vermiculite --> Mix
    Water --> Mix
    Mix --> Vermiculite_Concrete[Lightweight Vermiculite Concrete]
    Vermiculite_Concrete --> Properties[Low Density, Thermal Insulation, Low Strength]

Refer to IS 6461 Part 4 and lightweight concrete provisions for detailed design and testing.

IS 6461 Part 4 covers types of concrete including wet-mix shotcrete and provides a comprehensive list of contributors and contact information for BIS and affiliated organizations.

Contributors Include:

• Experts from Central Public Works Department, Concrete Association of India, Geological Survey of India, Cement Research Institute, and others.

BIS Headquarters:

Manak Bhavan, 9 Bahadur Shah Zafar Marg, New Delhi 110002

• Phone: 323 0131, 323 3375, 323 9402
• Fax: +91 011 3234062
• Email: bis@vsnl.com
• Website: http://wwwdel.vsnl.ret.in/bis.org

Regional and Branch Offices:

Note: Eastern Sales Office is at 5 Chowringhee Approach, Kolkata; Western Sales Office at Novelty Chambers, Mumbai; Bangalore Sales Office at Unity Building.

Summary for Practitioners:

• Use contacts for clarifications, updates, and purchasing standards.
• The glossary and concrete type definitions, such as wet-mix shotcrete, are detailed in this part.