Glossary of terms relating to cement concrete, Part 8: Properties of concrete

IS 6461 Part 8 (1973) — Introduction & Adoption: Key Points

• Purpose: Standardizes cement grout and mortar properties for structural use.
• Wettest Stable Consistency (Clause 2.86): Maximum water content at which grout/mortar adheres to vertical surfaces without sloughing.

Key Definitions:

Adoption:

• Developed by experts from Structural Engineering Research Centre, Cement Research Institute, National Buildings Organization, and other bodies.
• Regional and branch offices of BIS manage dissemination and sales.

Practical Notes:

• Use wettest stable consistency to ensure proper application on vertical surfaces.
• Contact nearest BIS office for full standard and detailed tables.

Quick Reference Formula (for grout consistency):

[ \text{Water content} \leq \text{Wettest stable consistency limit} ]

flowchart LR
    A[Mix Cement + Water] --> B{Check Consistency}
    B -- Water content ≤ Wettest Stable Consistency --> C[Apply on Vertical Surface]
    B -- Water content > Wettest Stable Consistency --> D[Sloughing Occurs - Adjust Water]

For detailed tables and structural aspects, refer to full IS 6461 Part 8 document via BIS.

IS 6461 Part 8: Purpose and Scope of the Glossary

• Purpose: To provide standardized definitions for terms related to cement concrete, ensuring uniform understanding across the industry.
• Scope: Covers terminology used in cement concrete technology, grouped into 12 parts for ease of reference.

Key Points:

• The glossary standardizes terms to avoid ambiguity in design, construction, and testing.
• It serves as a reference for engineers, contractors, and material suppliers.
• The glossary includes terms related to materials, mix design, properties, testing, and durability.

Structure:

• Divided into 12 parts, each focusing on specific aspects of cement concrete.
• Part 8 specifically addresses terms related to [context-specific area, e.g., admixtures, curing, or durability].

Example (typical format):

This standard does not provide formulas or tables but ensures clarity in terminology used in concrete technology.

flowchart LR
    A[IS 6461 Glossary] --> B{Grouped into 12 Parts}
    B --> C[Part 1: Materials]
    B --> D[Part 2: Mix Design]
    B --> E[Part 8: Specific Terms]
    B --> F[Part 12: Testing]

Summary: IS 6461 Part 8 defines and standardizes terms related to cement concrete, facilitating clear communication and consistent application in construction and research.

IS 6461 Part 8 (1973) - Absorption of Concrete

Definition (Clause 2.1)

• Absorption is the process where liquid penetrates and fills the permeable pores of a porous solid (concrete).
• It is measured as the increase in weight of the concrete specimen due to liquid uptake.

Key Formula for Absorption

[ \text{Absorption} (%) = \frac{W_{saturated} - W_{dry}}{W_{dry}} \times 100 ]

• ( W_{saturated} ) = Weight of concrete after immersion until saturation
• ( W_{dry} ) = Oven-dry weight of concrete specimen

Typical Specifications (from IS 6461 Part 8 & related concrete standards)

Lower absorption indicates denser, more durable concrete.

Importance

• High absorption leads to reduced durability due to ingress of harmful agents.
• Used to assess quality and durability of concrete.

flowchart LR
    A[Dry Concrete] --> B[Immersion in Water]
    B --> C[Water Penetrates Pores]
    C --> D[Increase in Weight]
    D --> E[Calculate Absorption %]

Summary: Absorption quantifies water uptake in concrete pores, critical for durability assessment. Use the weight difference formula and compare with specified limits for quality control.

IS 6461 Part 8 (1973) - Agglomeration in Hydraulic Cement

Definition:

• Agglomeration: The gathering of fine particles into a ball or mass, often relevant in cement and pozzolana processing.

Key Points:

• Agglomeration affects particle size distribution and reactivity of pozzolanic materials.
• Proper agglomeration improves workability and strength of cementitious mixes.

Specifications & Considerations (from general cement technology):

• Agglomerate size should be controlled to avoid weak zones.
• Typical agglomerate size ranges from 0.1 mm to 5 mm.
• Agglomeration influences water demand and setting time.

Related IS Code References:

• IS 6461 Part I: Concrete Aggregates — particle size and grading.
• IS 3812: Pulverized Fuel Ash (PFA) — grading and fineness.
• IS 1727: Methods of test for pozzolanic materials.

Formula (for estimating agglomerate impact on surface area):

[ S = \frac{6}{\rho \times d} ]

• (S) = specific surface area (m²/kg)
• (\rho) = density (kg/m³)
• (d) = average particle/agglomerate diameter (m)

Summary Table: Agglomeration Effects

flowchart LR
    A[Fine Particles] --> B[Agglomeration]
    B --> C[Increased Particle Size]
    C --> D[Lower Surface Area]
    D --> E[Reduced Reactivity]
    E --> F[Impact on Strength & Setting Time]

Note: For detailed test methods and limits, refer to IS 6461 Part I and IS 1727.

IS 6461 Part 8: Bleeding in Concrete/Mortar

Key Definitions:

• Bleeding (2.13): Autogenous flow or emergence of mixing water due to settlement of solids.
• Bleed (2.12): To undergo bleeding.
• Bleeding Capacity (2.14):
  [ \text{Bleeding Capacity} = \frac{\text{Volume of water released by bleeding}}{\text{Volume of paste or mortar}} ]
• Bleeding Rate (2.15): Rate at which water is released by bleeding (volume/time).

Practical Notes:

• Bleeding affects durability and surface finish.
• Excessive bleeding leads to segregation and weak surface layers.

Typical Values (from practice & literature):

Control Measures:

• Use well-graded aggregates.
• Optimize water-cement ratio.
• Use admixtures to reduce bleeding.

flowchart LR
  A[Mixing] --> B[Settlement of solids]
  B --> C[Water moves upward]
  C --> D[Water emerges as bleed water]

Summary: Bleeding capacity quantifies water released; bleeding rate measures speed. Control bleeding to ensure concrete quality and durability.

IS 6461 Part 8 - Bleeding Rate: Key Points

• Bleeding Rate (Clause 2.15) is the speed at which water separates from mortar or paste after placement.
• It is typically expressed as volume of water released per unit area per unit time (e.g., ml/cm²/min).

Important Related Terms:

Typical Formula for Bleeding Rate:

[ \text{Bleeding Rate} = \frac{\Delta V}{A \times \Delta t} ]

Where:

• (\Delta V) = Volume of water released (ml)
• (A) = Surface area of the sample (cm²)
• (\Delta t) = Time interval (min)

Practical Notes:

• Bleeding rate affects durability and finishing quality.
• Lower bleeding rates are preferred to reduce segregation and surface defects.

flowchart LR
    A[Mixing of Mortar/Paste] --> B[Placement]
    B --> C[Settlement of Solids]
    C --> D[Water Separation]
    D --> E[Water Emergence at Surface (Bleeding)]
    E --> F[Measure Volume & Time]
    F --> G[Calculate Bleeding Rate]

This diagram illustrates bleeding as a process from mixing to measurement.

Consistency Factor (IS 6461 Part 8, Clause 2.22):

• It quantifies grout fluidity, analogous to viscosity.
• Measured in the lab using a torque viscosimeter.
• Reported as degrees of rotation indicating ease of grout flow into pores/fissures.

Key Points:

Related Concepts:

• Consistency (Clause 2.21): Flow/slump tests for concrete/mortar.
• Compacting Factor (Clause 2.17): Ratio of weight of concrete filled by standard fall to weight after rodding compaction (IS 1199-1959).

Typical Use:

• Higher consistency factor → more fluid grout.
• Helps in selecting grout mix for effective pumping and penetration.

flowchart LR
    A[Grout Sample] --> B[Torque Viscosimeter]
    B --> C[Measure Torque]
    C --> D[Degrees of Rotation = Consistency Factor]
    D --> E[Assess Grout Fluidity]

This factor guides grout mix design for adequate flow without segregation.

IS 6461 Part 8 (1973) - Creep Key Points

Definitions:

• Creep (2.24): Time-dependent deformation under sustained load.
• Creep Strength (2.71): Stress causing a specified creep over time at a given temperature.

Key Concepts:

• Creep is irrecoverable deformation increasing with time under constant stress.
• Important for concrete and cementitious materials under long-term loads.

Typical Creep Formula (General Engineering Practice):

[ \epsilon_c(t) = \epsilon_{immediate} + \epsilon_{creep}(t) ] Where:

• (\epsilon_c(t)) = total strain at time (t)
• (\epsilon_{immediate}) = instantaneous elastic strain
• (\epsilon_{creep}(t)) = creep strain over time (t)

Creep Coefficient:

[ \phi(t) = \frac{\epsilon_{creep}(t)}{\epsilon_{immediate}} = \frac{\text{creep strain}}{\text{initial elastic strain}} ]

Typical Creep Behavior:

graph LR
A[Load Applied] --> B[Instantaneous Elastic Strain]
B --> C[Creep Strain Increases Over Time]
C --> D[Total Strain = Elastic + Creep]

Specifications:

• Creep depends on stress level, temperature, material composition, and time.
• IS 6461 Part 8 focuses on cement and concrete creep under specified conditions.
• Testing uses a truncated cone specimen for consistency (Clause 2.43).

Practical Notes:

• Use creep coefficients from IS or related codes for design.
• Monitor long-term deformation in structural elements.

For detailed values and test procedures, refer to IS 6461 Part 8 tables and annexures.

Drying Shrinkage in IS 6461 Part 8 refers to contraction due to moisture loss (Clause 2.27). Key definitions:

• Initial Drying Shrinkage (2.45):
  [ \text{Initial Drying Shrinkage} = \frac{L_{\text{moist}} - L_{\text{dry}}}{L_{\text{moist}}} \times 100% ]
  where (L_{\text{moist}}) = length after curing, (L_{\text{dry}}) = length after drying to constant length.

• Shrinkage (2.66):
  Volume decrease over time due to drying and chemical changes, independent of temperature or external load.

• Setting Shrinkage (2.64):
  Volume reduction before final set due to particle settling and chemical water binding.

Typical Drying Shrinkage Values (approximate from IS codes & literature):

Important Notes:

• Shrinkage strain is measured on standard specimens (usually prisms/cylinders) cured under specified conditions.
• Drying shrinkage is time-dependent and increases with drying duration.
• Control by mix design, curing, and moisture protection.

flowchart LR
    A[Moist Specimen Length] --> B[Drying Process]
    B --> C[Moisture Loss]
    C --> D[Volume Reduction]
    D --> E[Drying Shrinkage Strain]

For detailed formulas on shrinkage strain over time, refer to IS 6461 Part 8 Annexures or related IS codes on concrete testing.

Key Formulas and Specifications for Elasticity (IS 6461 Part 8 - 1973):

• Elasticity (Clause 2.31):
  Property of material to recover original shape immediately after load removal.

• Elastic Modulus, E (Clause 2.32):
  [ E = \frac{\text{Normal Stress}}{\text{Strain}} \quad \text{(within proportional limit)} ]
  Also known as Young's modulus.

• Effective Modulus of Elasticity, (E_{ert}) (Clause 2.30):
  Accounts for combined elastic-plastic behavior in structures:
  [ E_{ert} = \frac{1 + 0.4 \left(\frac{E_C}{E_j}\right)}{1 + \frac{E_C}{E_j}} ]
  Where:

  • (E_C) = Modulus of elasticity of concrete
  • (E_j) = Modulus of elasticity of foundation rock

Typical Values (for reference):

flowchart LR
    A[Load Applied] --> B[Material Deforms]
    B --> C[Load Removed]
    C --> D[Material Recovers Shape (Elasticity)]
    D -->|Stress/Strain| E[Elastic Modulus E]
    E --> F[Effective Modulus \(E_{ert}\)]

This summarizes elasticity per IS 6461 Part 8, useful for structural analysis involving concrete and foundation interaction.

Elastic Modulus (E) - IS 6461 Part 8 Highlights

• Definition (Clause 2.32):
  Elastic Modulus, E, is the ratio of normal stress to strain within the proportional limit (tensile or compressive).
  [ E = \frac{\sigma}{\varepsilon} ] where:
  (\sigma) = normal stress,
  (\varepsilon) = strain.

• Effective Modulus of Elasticity (Clause 2.30):
  Accounts for combined concrete and foundation rock effects:
  [ E_{ert} = \frac{1 + 0.4 \left(\frac{E_C}{E_j}\right)}{1 + \frac{E_C}{E_j}} ] where:
  (E_C) = modulus of elasticity of concrete,
  (E_j) = modulus of elasticity of foundation rock.

• Elasticity (Clause 2.31):
  Property enabling material to recover original shape immediately after load removal.

Typical Values (IS 456 for reference):

Summary Diagram

graph LR
A[Stress (σ)] -- proportional --> B[Strain (ε)]
B -- ratio --> C[Elastic Modulus (E = σ/ε)]
C -- combined with foundation --> D[Effective Modulus (Eert)]

Note: Use (E) within proportional limit; beyond that, plastic behavior dominates. Effective modulus adjusts for foundation interaction.

Initial Drying Shrinkage (IS 6461 Part 8)

• Definition (Clause 2.45):
  [ \text{Initial Drying Shrinkage} = \frac{L_{\text{moist}} - L_{\text{dried}}}{L_{\text{moist}}} \times 100% ] where:

  • (L_{\text{moist}}) = Length of specimen after curing (moist condition)
  • (L_{\text{dried}}) = Length after drying to constant length

• Related Terms:

  • Drying Shrinkage (2.27): Volume contraction due to moisture loss.
  • Shrinkage (2.66): Volume decrease over time due to drying and chemical changes, independent of temperature/stress.
  • Setting Shrinkage (2.64): Volume reduction before final set from solid settling and chemical water binding.

Typical Test Setup & Measurement:

• Specimens cured under controlled conditions (e.g., 28 days moist curing).
• Length measured initially (moist) and after drying at standard conditions (e.g., 50% RH, 23°C) until constant length.

Important Notes:

• Initial drying shrinkage is critical for crack control and durability.
• Values vary with mix design, curing, and environmental conditions.

flowchart LR
  A[Specimen Moulded & Cured] --> B[Measure Length L_moist]
  B --> C[Dry to Constant Length]
  C --> D[Measure Length L_dried]
  D --> E[Calculate Shrinkage %]

For detailed values, refer to IS 6461 Part 8 tables for typical shrinkage percentages based on mix and curing.

IS 6461 Part 8: Initial Setting Time

Definitions (Clauses)

• Initial Setting Time (2.47): Time for cement paste/mortar/concrete to start stiffening.
• Initial Set (2.46): Empirical time when cement paste resists penetration by a weighted needle, indicating the start of stiffening.
• Final Setting Time (2.40): Time when the paste/mortar/concrete achieves final set (complete stiffening).

Key Specifications

• Test Method: Penetration resistance test using Vicat apparatus.
• Initial Setting Time Limit: Typically, initial setting time should not be less than 30 minutes to allow proper handling.
• Penetration Resistance at Initial Set: About 3.5 MPa (or as per IS 4031 Part 5).

Typical Formula for Setting Time (Empirical)

No direct formula; determined experimentally by:

[ t_i = \text{Time when penetration resistance} \geq 3.5 , \text{MPa} ]

Summary Table (Typical Values)

flowchart LR
    A[Fresh Cement Paste] --> B{Penetration Resistance}
    B -->|< 3.5 MPa| C[Not Set]
    B -->|≥ 3.5 MPa| D[Initial Set Achieved]
    D --> E{Further Hardening}
    E -->|Final Set| F[Final Setting Time]

Note: Use IS 4031 (Part 5) for detailed test procedures on setting times.

IS 6461 Part 8 (1973) - Key Points on "Set"

• Definition (Clause 2.63):
  Set is the stage where cement paste, mortar, or concrete loses plasticity to a certain extent, measured by resistance to penetration or deformation.

  • Initial Set: First noticeable stiffening.
  • Final Set: Attainment of significant rigidity.

• Related Sets:

  • Grab Set (2.44): See Clause 2.41 (likely a specific test or condition).
  • Quick Set (2.56): See Clause 2.36 (rapid stiffening).
  • Rubber Set (2.62): See Clause 2.41 (elastic-like behavior).

Typical Test for Setting Time (IS 6461 references IS 4031 Part 5 or IS 269):

Vicat Needle Test (Simplified):

• Initial set when penetration = 33 mm
• Final set when needle fails to penetrate 0.5 mm

graph LR
A[Plastic Cement Paste] --> B[Initial Set (Stiffening)]
B --> C[Final Set (Rigid)]

Summary: "Set" defines the transition from plastic to rigid state, crucial for timing construction operations. Use Vicat needle test per IS 4031 for measurement.

Wagner Fineness (IS 6461 Part 8)

• Definition: Wagner Fineness quantifies the fineness of cement as total surface area (cm²/g) measured by the Wagner turbidimeter.

• Key Concept:
  Fineness (cm²/g) = Total surface area of cement particles per gram, indicating particle size distribution and affecting hydration rate.

• Measurement:
  Using the Wagner turbidimeter apparatus, the turbidity of a cement suspension is measured, correlating to surface area.

Typical Procedure Summary:

1. Prepare a standard suspension of cement in water.
2. Measure turbidity using the Wagner turbidimeter.
3. Calculate surface area from turbidity using calibration curves.

Important Notes:

• Wagner Fineness is related to Turbidimeter Fineness (Clause 2.81) but specific to the Wagner apparatus.
• Units: cm²/g (surface area per gram)
• Higher fineness → faster hydration and strength gain.

Related Parameters:

flowchart LR
    Cement Sample --> Suspension Preparation
    Suspension Preparation --> Wagner Turbidimeter
    Wagner Turbidimeter --> Turbidity Measurement
    Turbidity Measurement --> Surface Area Calculation
    Surface Area Calculation --> Wagner Fineness (cm²/g)

For detailed calibration and test procedure, refer to IS 6461 Part 8 (1973) and IS 1199 for related concrete testing methods.