Guidelines for Use of Iron, Steel and Copper Slag in the Construction of Rural Roads

IRC SP 121 - Scope & Key Specifications Summary

Scope:
IRC SP 121 covers the use of various slags (Iron & Steel Slag, Copper Slag) in pavement construction, including their physical, chemical, and geotechnical properties, design, and specifications for embankments, subgrade, base, and drainage layers.

Key Specifications & Procedures:

• Sieves for Gradation (Clause 31.5 d):
  Standard IS sieve sizes:

  • 31.5 mm, 26.5 mm, 13.2 mm, 4.75 mm, 2.36 mm, 500 µm, 75 µm

• Expansion Measuring Apparatus (Clause 31.5 e):
  As per Fig. A1 (refer to IRC SP 121 Annexure for details).

• Specimen Preparation (Clause 4.1):

  • Use collar, perforated base plate, spacer disc, and filter paper.
  • Moisture content samples ≥ 500 g; prepare new specimens if moisture deviates >1% from optimum.
  • Fill mould in 3 layers with ~50 mm falling height, ram each layer 92 times from 450 mm height.
  • Remove collar, shave excess, fill holes with fine material, reform surface.
  • Turn mould upside down, remove spacer disc, reattach perforated base plate with filter paper.
  • Calculate wet density:

  [ \text{Wet Density} = \frac{\text{Mass of Rammed Specimen}}{\text{Volume of Mould}} ]

Table: Typical IS Sieves for Slag Gradation

flowchart TD
    A[Prepare Mould] --> B[Attach Collar & Base Plate]
    B --> C

Blast Furnace Slag (BFS) - Key Points from IRC SP 121

1. Definition

• BFS is a non-metallic byproduct from pig iron production.
• Mainly composed of silicates, alumina-silicates, and calcium-alumina-silicates.
• Constitutes ~20% by mass of iron production.

2. Types of BFS by Cooling Method

3. Chemical Composition (Typical % from Indian Steel Plants)

4. Engineering Properties

• Physical properties vary with cooling method.
• Granulated slag is reactive and used as supplementary cementitious material.
• Air-cooled slag is used as aggregate due to hardness.
• Expanded slag is lightweight and used for insulation or lightweight concrete.

flowchart LR
    A[Molten Slag] --> B{Cooling Method}
    B --> C[Air Cooling]
    B --> D[Controlled Water Cooling]
    B --> E[Rapid Water Quenching]
    C --> F[Air-cooled Slag]
    D --> G[Granulated Slag]
    E --> H[Expanded Slag]

Summary: BFS chemical composition is fairly consistent, but physical properties depend on cooling. Use granulated slag for cementitious applications; air-cooled slag for aggregates; expanded slag for lightweight materials.

Electric Arc Furnace Slag (EAFS) - Key Specifications from IRC:SP:121-2018

Physical & Engineering Properties (Table 2 Summary)

Key Characteristics:

• Strong, dense, non-porous, cubical shape
• Excellent resistance to polishing and rutting
• Good affinity to bitumen — ideal for bituminous surface treatments
• Contains 10-20% metallic iron; metal-free slag used after magnetic separation
• Vesicular surface promotes particle interlock and high shear strength

Usage Notes:

• Use EAFS as coarse and fine aggregates in bituminous mixes for durable, skid-resistant pavements.
• Ensure compliance with specified moisture content and density for compaction.

flowchart LR
    A[Steel Making Process] --> B[Electric Arc Furnace]
    B --> C[Steel Slag Produced]
    C --> D[Magnetic Separation]
    D --> E[Metallic Iron Removed]
    E --> F[Crushing & Screening

Key Chemical Composition & Engineering Properties from IRC:SP:121-2018

1. Chemical Composition of Slags (% by weight)

BF = Blast Furnace Slag, Steel Slag = Basic Oxygen Furnace/ Electric Arc Furnace Slag

2. Engineering Properties of Slags (Typical Ranges)

Key Specifications & Formulas for Slag as Pavement Material (IRC SP 121)

1. Slag Usage in Pavement Layers

• Unbound Layers: Granular Subbase & Base (particle interlock, shear strength)
• Bound Layers: Stabilized Subbase & Base (chemical bonding + particle interlock)
• Asphalt & Concrete Layers: Aggregates for surface courses and PCC

2. Important Properties of Slag Aggregates

• Higher density (~20% more than conventional aggregates)
• Cubical shape with fractured faces → better mechanical interlock
• Higher skid resistance (better friction)
• Higher affinity to bitumen → lower stripping

3. Applications (Table 5 Summary)

Note: Increase binder content by 0.5% for slag aggregates in bituminous surfacing due to vesicular nature.

4. Stabilization Design Parameter (IRC:37)

• Elastic Modulus, E (MPa) = 1000 × UCS (MPa)
  Where UCS = Unconfined Compressive Strength after 28 days curing

Summary Diagram: Slag in Pavement Layers

graph TD
    A[Slag as Pavement Material] --> B[Unbound Layers]
    A --> C[Bound Layers]
    A --> D[Asphalt & Concrete Layers]
    B --> B1[Granular Subbase]
    B --> B2[Granular Base]
    C --> C1[Stabilized Subbase/Base]
    D --> D1[Bituminous Surfacing]
    D --> D2[Concrete Pavement]

For detailed design,

Mechanical Stabilisation of Copper Slag (IRC SP 121 - Clause 4.1)

Copper slag alone is cohesionless and poorly graded, making compaction and embankment construction difficult. Mechanical stabilization by mixing with local soil or pond ash improves:

• Gradation
• Dry density
• Shear strength (c, φ)
• California Bearing Ratio (CBR)

Key Specifications & Parameters (from Table 3):

* For Black Cotton Soils

Important Notes:

• PI < 45 as per MoRD specifications.
• Mix proportions must be optimized through laboratory tests for best performance.
• Mechanical stabilization enhances embankment stability and durability.

flowchart LR
    A[Copper Slag (Cohesionless)] --> B[Mix with Soil / Pond Ash]
    B --> C[Improved Gradation & Density]
    C --> D[Enhanced Shear Strength (c, φ)]
    D --> E[Better CBR & Permeability]
    E --> F[Suitable for Embankment Construction]

This approach ensures embankment materials meet IRC and MoRD standards for

Earth Cover for Protection of Slopes (IRC SP 121 - Clause 4.2 & 14.4)

• Purpose: Prevent erosion of copper slag-soil/fly ash stabilized embankment slopes.

• Thickness of Earth Cover:

  • Embankment height ≤ 3 m:
    • Horizontal thickness = 0.3 m
    • Minimum dry density = 14.4 kN/m³
  • Embankment height > 3 m:
    • Horizontal thickness = 0.5 m
    • Minimum dry density = 15.2 kN/m³
    • Intermediate soil layers of 0.2 m thickness every 2 m height recommended for feasibility.

• Soil Properties:

  • Plasticity Index (PI) = 10 to 20
  • Must comply with MoRD Section 301 specifications.
  • When used as subgrade, dry density ≥ 16.5 kN/m³

• Construction Note:
  Side earth cover must be placed simultaneously with copper slag-soil/fly ash core; adding later is prohibited.

Summary Table

This ensures slope stability and erosion resistance for copper slag embankments.

IRC SP 121: Site Investigation Key Points

1. Scope of Site Investigation (Clause 5.1)

• Investigate in-situ soil characteristics to assess suitability for copper slag embankment.
• Collect data on:
  • Local soils/wastes availability (quantity, location, lead distance).
  • Topography via total station survey for embankment profile & quantity estimation.
  • Hydrological data: rainfall & groundwater for drainage design and slope stability evaluation.
• Conduct subsoil investigation to at least 2× embankment height depth to determine:
  • Soil/rock strata nature and extent.
  • Bulk density.
  • Shear strength parameters (cohesion c, angle of internal friction φ).

2. Key Parameters for Stability & Design

3. General Formula for Slope Stability Factor of Safety (FOS)

[ FOS = \frac{c' \cdot L + (W \cos \alpha - uL) \tan \phi'}{W \sin \alpha} ] Where:

• (c') = effective cohesion
• (L) = length of slip surface
• (W) = weight of sliding mass
• (\alpha) = slope angle
• (u) = pore water pressure

4. Additional Recommendations

• Use site-specific data for drainage design to prevent pore pressure increase.
• Mix copper slag with fly ash/local soil as per availability and geotechnical compatibility (Clause 4.1).
• Follow Clause 3.2 for geotechnical characteristics and Clause 5.2 for slope stability analysis.

flowchart TD
    A[Site Investigation]
    A --> B[Local Soils & Wastes Availability]
    A --> C[Topography Survey]
    A --> D[Hydrological Data Collection]
    A --> E[Subsoil Investigation]
    E --> F[Bulk Density]
    E --> G[Shear Strength (c, φ)]

Key Specifications & Formulas for Slag as Subgrade Material (IRC SP 121):

1. Types of Slag Used

• Steel Slag (BOFS, EAFS, ACBFS): Preferred for better strength, abrasion, impact resistance.
• Blast Furnace Slag (GBFS): Less preferred for bituminous surfacing.

2. Important Characteristics

• Higher skid resistance (due to higher friction).
• Steel slag density ~20% higher than conventional materials.
• Cubical shape with fractured faces → good mechanical interlock.
• Higher bitumen affinity → lower stripping.

3. Usage Table (Excerpt from Table 5)

4. Binder Content Adjustment

• Increase binder content by 0.5% over MoRD specs when using slag due to vesicular nature.

5. Stabilisation & Elastic Modulus

• Elastic Modulus (E) related to UCS by:

[ \boxed{E = 1000 \times UCS} ]

Where:

• (E) = Elastic Modulus (MPa)
• (UCS) = Unconfined Compressive Strength (MPa) after 28 days curing

Summary Diagram: Slag Use in Pavement Layers

graph TD
    A[Slag Types] --> B[Steel Slag]
    A --> C[Blast Furnace Slag]
    B --> D[Bituminous Surfacing]
    B --> E[Granular Base/Sub-base]
    C --> F[Limited to Stabilised Sub-base & Concrete]
    D --> G[Increase Binder by 0.5%]

References:

• IRC SP 121: Clause 6.1, Table 5
• IRC:37 (Elastic modulus formula)

Slag as Shoulder Material — IRC SP 121 Key Points

1. Applications of Slag in Pavement Layers (Fig.7)

• Steel/Iron slag used in:
  • Shoulder (steel slag fines + soil)
  • Granular Subbase (GSB)
  • Open Graded PMC (from steel/iron slag)
• Soil cover needed if fines content is high in embankment/subgrade mixed with slag.

2. Properties of Slag Aggregates (Clause 2.3)

• Steel slag advantages:
  • 20% higher density than traditional aggregates
  • Cubical shape with fractured faces → better interlock
  • Higher friction → better skid resistance
  • Better bitumen affinity → lower stripping
• Binder content for bituminous surfacing with slag should be increased by 0.5% over normal MoRD values.

3. Typical Uses of Slag (Table 5 Summary)

4. Stabilisation & Design Parameters (Clause 3)

• Elastic Modulus (E) for slag-bound materials:

  [ E = 1000 \times UCS ]

  Where:

  • (E) = Elastic Modulus (MPa)
  • (UCS) = Unconfined Compressive Strength after 28 days (MPa)

flowchart TD
    A[Slag Material] --> B[Shoulder: Steel slag fines + soil]
    A --> C[Granular Subbase (GSB)]
    A --> D[Open Graded PMC]
    B --> E[Soil cover if fines high]
    C --> F[Unstabilised or Stabilised]
    D -->

Specifications for Copper Slag in Water Bound Macadam (WBM) - IRC SP 121

Key Points:

• Copper Slag Proportion in WBM:

  • Coarse copper slag can replace up to 50% of 10 mm aggregates in 'Type B' screenings.
  • Must satisfy MoRD gradation requirements for screenings (Table 400.12).

• Mixing Guidelines:

  • Fine slag may be mixed with conventional aggregates (40 mm, 20 mm, 10 mm, stone dust) in 20-30% proportion for Wet Mix Macadam (WMM).
  • If fine slag unavailable, stone dust is used.

• Cement Stabilisation:

  • Copper slag (coarse) can be cement stabilized with 3-6% cement.
  • Copper slag content in mixes can be up to 75%.
  • Required UCS (Unconfined Compressive Strength) after 7 days curing:
    • 1.7 MPa for sub-base
    • 3.0 MPa for base layer (as per IRC:SP:72)

Gradation & Replacement Summary (per MoRD Tables 400.1A, 400.1B, 400.12):

Additional Notes:

• Copper slag mixtures exhibit good permeability, suitable for drainage layers.
• Laboratory testing (7-day UCS) is mandatory for stabilised mixes.
• Gradation must comply with MoRD specifications to ensure performance.

flowchart LR
    A[Conventional Aggregates] --> B[Mix with Copper Slag]
    B --> C{Copper Slag Type}
    C -->|Coarse| D[Replace up to 50% of 10 mm aggregate in WBM]
    C -->|Fine or Fine+Coarse| E[Replace 20-30% in WMM]

Specifications for Copper Slag in Wet Mix Macadam (WMM) – IRC SP 121

1. Gradation and Mix Proportion (Clause 9.2)

• Copper slag (fine/coarse/fine+coarse) can replace 20-30% of conventional aggregates (40 mm, 20 mm, 10 mm, stone dust).
• If fine slag unavailable, use stone dust.
• Gradation must meet MoRD Table 400.12 for WMM.

2. Mix Preparation & Compaction (Clause 11.3)

• Use conventional WMM plant; adjust to achieve uniform design gradation.
• Wet mix at Optimum Moisture Content (OMC) is non-plastic.
• Compact immediately with rollers to avoid segregation.
• Physical and gradation requirements follow MoRD Section 400.

3. Cement Stabilized Copper Slag (Clause 1.7)

• Copper slag content in mixes ~ 75%.
• Cement content: 3-6%.
• Design UCS (7-day cured) targets:
  • 1.7 MPa for sub-base
  • 3.0 MPa for base layer (per IRC:SP:72)

4. Water Bound Macadam (Clause 9.1)

• Coarse copper slag can replace 50% of 10 mm aggregates in 'Type B' screenings.
• Must satisfy MoRD gradation requirements.

Key Table: Typical Gradation Limits for WMM (MoRD Table 400.12)

flowchart LR
  A[Conventional Aggregates + Copper Slag (20-30%)] --> B[Mixing in WMM Plant]
  B --> C[Wet Mix @ OMC (Non-Plastic)]
  C -->

Key Specifications for Copper Slag in Bituminous Surface Courses (IRC SP 121):

1. Gradation & Mixing (Clause 9.2 & 7)

• Copper slag (fine/coarse or combined) can replace 20-30% of conventional aggregates (40 mm, 20 mm, 10 mm, stone dust) in Wet Mix Macadam (WMM).
• For granular sub-base, 30-50% replacement of fine aggregates by copper slag is allowed.
• If fine slag is unavailable, use stone dust.

2. Cement Stabilized Mix (Clause 8)

• Copper slag content ~ 75% in sub-base/base layers.
• Cement content: 3-6%.
• Design UCS (Unconfined Compressive Strength):
  • Sub-base: ≥ 1.7 MPa
  • Base: ≥ 3 MPa (IRC:SP:72)
• 7-day UCS test mandatory for design validation.

3. Volumetric Expansion Ratio (Clause 5)

[ E = 100 \times \frac{D_f - D_i}{H} ]

• (E): volumetric expansion ratio (%)
• (D_f): last dial gauge reading (mm)
• (D_i): first dial gauge reading (mm)
• (H): initial specimen height = 125 mm

Average over 3 specimens, round to 1 decimal place.

4. Permeability & Drainage (Clause 6.3)

• Copper slag mixtures show good permeability, suitable for drainage layers.

Summary Table: Copper Slag Usage in Road Layers

flowchart LR
    A[Conventional Aggregates] -->|20-30% replaced| B[Copper Slag in WMM]
    C[Fine Aggreg

IRC SP 121: Method Statement for Construction — Key Points

1. Specimen Preparation (Clause 4.1)

• Use mould with collar, perforated base plate, spacer disc, and filter paper.
• Moisture content measured on two 500g samples; if ±1% from optimum moisture, remake specimens.
• Sample poured in 3 layers with ~50 mm falling height.
• Ram each layer uniformly 92 times from 450 mm height on a rigid flat surface.
• Remove collar, shave excess, fill holes with fine materials, reform surface.
• Turn mould upside down gently, remove spacer and base plate, reattach filter paper.
• Clean specimen outside, measure total mass.
• Calculate wet density:
  [ \text{Wet Density} = \frac{\text{Mass of specimen}}{\text{Volume of mould}} ]

2. Sieves for Testing (Clause 31.5 d)

• IS Sieves sizes:
  • 31.5 mm
  • 26.5 mm
  • 13.2 mm
  • 4.75 mm
  • 2.36 mm
  • 500 µm
  • 75 µm

3. Seal Coat Usage (Clause 10.2)

• Open Graded Premix Carpet/Bituminous Macadam void sealing.
• Copper slag replacement:
  • 60-70% for Type B premixed seal coat.
  • 20-25% for Type A (liquid) and Type C seal coats.

4. Expansion Measuring Apparatus (Clause 31.5 e)

• Refer Fig. A1 (not provided here) for apparatus setup.

Summary Diagram: Specimen Preparation Steps

flowchart TD
    A[Attach collar & base plate] --> B[Place spacer disc & filter paper]
    B --> C[Measure moisture content]
    C --> D[Pour sample in 3 layers]
    D --> E[Ram each layer 92 times from 450mm height]
    E --> F[Remove collar & shave excess]
    F --> G[Fill holes & reform surface]
    G --> H[Turn mould upside down, remove spacer & base]
    H --> I[Attach filter paper & base plate

Quality Control Tests as per IRC SP 121 (Ref: IS:383-2016)

Key Specifications & Procedures

• Sieves (Clause 31.5 d):
  Use IS sieves of sizes:
  31.5 mm, 26.5 mm, 13.2 mm, 4.75 mm, 2.36 mm, 500 µm, 75 µm

• Specimen Preparation (Clause 4.1):

  • Attach collar & perforated base plate, place spacer disc and filter paper.
  • Moisture content test on two 500 g samples; if moisture differs by ≥1% from optimum, prepare new specimens.
  • Fill mould in 3 equal layers, ramming each with 92 free drops of 4.5 kg rammer from 450 mm height on rigid base.
  • Remove collar, shave excess, fill holes with fine material, reform surface.
  • Turn mould upside down, remove spacer & base plate, reattach filter paper and base plate.
  • Measure total mass, calculate wet density:
    [ \text{Wet Density} = \frac{\text{Mass of specimen}}{\text{Volume of mould}} ]

• Expansion Measuring Apparatus (Clause 31.5 e):
  Follow Fig. A1 for apparatus setup (not shown here).

Additional Tests (Referenced Standards)

Summary Diagram: Specimen Preparation Steps

flowchart TD
    A[Attach collar & base plate] --> B[Place spacer disc & filter paper]
    B --> C[Measure moisture content on 2 samples]
    C --> D{Moisture within 1% of optimum?}
    D -- No --> B