Guidelines for Cement Grouted Bituminous Mix Surfacing for Urban Roads

IRC SP:125-2019 — Introduction Key Points & Specifications

1. Cement Grouted Bituminous Macadam (CGBM) Overview

• Combines high voids bituminous mix with cementitious grout.
• Grout flowability and strength optimized for full penetration and durability.

2. Key Formulas for Mix Design

• Maximum Specific Gravity (Gmm):

Where:

• A = Mass of dry sample in air (g)

• B = Mass of bowl under water (g)

• C = Mass of bowl + sample under water (g)

• D, E = Masses related to lid, bowl, flask with/without sample (g)

• Air Voids (Va) and Voids in Mineral Aggregate (VMA):

[ Va = \left(1 - \frac{G_{mb}}{G_{mm}}\right) \times 100 ]

[ VMA = 100 - \frac{G_{mb} \times P_s}{G_{sb}} ]

Where:

• (G_{mb}) = Bulk specific gravity of compacted mix
• (G_{mm}) = Maximum specific gravity
• (P_s) = Percent aggregate in mix
• (G_{sb}) = Bulk specific gravity of aggregate

3. Recommended Properties for CGBM (Table Summary)

IRC SP 125: Scope - Key Formulas, Tables & Specifications

Scope (Clause 2):
Covers design, testing, and quality control of Cement Grouted Bituminous Mix (CGBM) for pavement surfacing.

Key Formulas for Specific Gravity (Annexure D)

Important Tables & Specifications

Key Materials Specifications & Formulas from IRC:SP:125-2019 for CGBM

1. Aggregates

• Specific Gravity (Gsb): Typically 2.7; if >2.7, minimum bitumen content can be reduced (Clause 2.7).
• Aggregate Gradation: CGBM Gr-I, Gr-II, Gr-III or any grading giving 25-35% air voids (Table 3).

2. Bitumen

• Binder content: Minimum 3.25% or as per drain down test (Table 3).

3. Cementitious Grout

• Cement: OPC 43 or OPC 53 (IS 8112, IS 12269)
• Fly ash: IS 3812 part 2, min. 65% passing 45 microns
• Initial setting time: 4-5 hrs (IS 4031 Part 5)
• Final setting time: 6-10 hrs (IS 4031 Part 5)
• Compressive strength @ 28 days: 40-100 N/mm² (ASTM C109)
• Flexural strength @ 28 days: 5-7 N/mm² (IS 4031 Part 8)
• Fluidity (Marsh Flow Value): 20-50 sec (ASTM C939)

4. CGBM Composite Properties

5. Air Voids and V

Coarse Aggregate Specifications — IRC SP 125

• Size: Retained on 2.36 mm sieve, cubical shape, clean, hard, durable, free from dust & deleterious materials.

• Physical Requirements (Table 1):

• Additional Notes:
  • Polished Stone Value not required for 19 mm CGBM.
  • Use anti-stripping agents if retained tensile strength < 80%.
  • Los Angeles Abrasion < 30% or Aggregate Impact Value < 24% to prevent crushing during compaction.

Summary Flow of Aggregate Selection

flowchart TD
    A[Start: Select Coarse Aggregate] --> B{Retained on 2.36 mm sieve?}
    B -- Yes --> C{Clean, hard, cubical?}
    C -- Yes --> D{Meets Physical Tests?}
    D -- Yes --> E[Use Aggregate]
    D -- No --> F[Reject or Treat Aggregate]
    C -- No --> F
    B -- No --> F

This ensures durable, stable aggregate for Cement Grouted Bituminous Mixes per IRC SP 125.

Key Specifications for Fine Aggregate (IRC SP 125):

• Size: Passing 2.36 mm sieve and retained on 75 µm sieve (IS:2386 Part 1).
• Source: 100% crushed, manufactured sand from stone crushing.
• Quality:
  • Clean, hard, durable, fairly cubical shape.
  • Free from soft pieces, organic, or deleterious substances.
• Tests & Limits:
  • Sand Equivalent Test (IS:2720 Part 37): ≥ 50
  • Plasticity Index (fraction passing 0.425 mm sieve, IS:2720 Part 5): ≤ 4

Additional Related Physical Requirements (from Coarse Aggregate Table 1 for reference):

Summary Formula for Plasticity Index (PI):

[ PI = LL - PL ]

Where:

• LL = Liquid Limit
• PL = Plastic Limit

For fine aggregate fraction passing 0.425 mm sieve, PI ≤ 4.

flowchart LR
    A[Fine Aggregate] --> B[Size: 2.36 mm to 75 µm]
    A --> C[100% Crushed Stone Sand]
    A --> D[Clean, Hard, Durable]
    A --> E[Sand Equivalent ≥ 50

Key Formulas & Specifications for Bitumen in CGBM (IRC:SP:125-2019)

1. Bitumen Type & Grade (Clause 3.3)

• Use Viscosity Grade Bitumen: VG-30 or VG-40 (IS:73)
• Or Polymer Modified Bitumen (PMB) Grade 40 (IRC:SP:53)

2. Mix Design Formulas (Clause 4.6)

• Percent Air Voids (Va): [ Va = \left(1 - \frac{G_{mb}}{G_{mm}}\right) \times 100 ]

• Voids in Mineral Aggregate (VMA): [ VMA = 100 \times \left(1 - \frac{G_{mb}}{P_s \times G_{sb}}\right) ]

Where:

• (G_{mb}) = Bulk specific gravity of compacted mix
• (G_{mm}) = Theoretical maximum specific gravity of mix
• (G_{sb}) = Bulk specific gravity of aggregate
• (P_s) = Percent aggregate in mix

3. Bitumen Content

• Minimum bitumen content: 3.25% or as per drain down test
• Adjusted for aggregate specific gravity > 2.7 (may reduce bitumen content)

4. Recommended Properties for CGBM (Table 3 Highlights)

Key Specifications & Formulas for Cementitious Grout (IRC SP 125 - Clause 3.5):

• Constituents: Cement, fine sand (passing 600 µm sieve), micro silica (silica fume), fly ash, water, superplasticizer, and optional polymer additives.

• Typical Mix Proportions (by weight):

  • Cement : Sand : Micro silica : Fly ash = 40 : 40 : 10 : 10
  • Water/Binder ratio (w/b) = 0.55
  • Superplasticizer = 0.5% of dry powder weight

  Alternate mix:
  Cement : Sand : Micro silica : Fly ash = 38 : 10 : 10 : 42
  w/c = 0.25, Superplasticizer = 0.3%

• Performance Criteria:

  • Flowability: Measured by Marsh Flow Cone (ASTM C939) — 45-50 seconds
  • Compressive Strength @ 28 days: 40-100 MPa (ASTM C109, 50x50x50 mm cube)
  • Flexural Strength @ 28 days: 10 MPa (IS 4031 Part 8, 160x40x40 mm)
  • Setting Time: Initial and final as per IS 4031 Part 6

• Design Notes:

  • Optimize sand and fly ash content for flow and strength.
  • Use superplasticizers to reduce water content while maintaining fluidity.
  • Polymer additives improve early strength.
  • Multiple trial mixes recommended due to material variability.

Summary Table: Grout Properties

Key Specifications & Design Guidelines for Cementitious Grout (IRC SP 125 - Clause 3.5)

Composition:

• Cement, fine sand (passing 600 µm sieve)
• Mineral additives: fly ash, micro silica (silica fume)
• Chemical additives: superplasticizer (0.3-0.5% by dry powder weight), polymer additives
• Water/binder ratio: ~0.25 to 0.55 depending on mix

Recommended Mix Proportions (by weight):

Performance Criteria:

Testing Notes:

• Flowability measured by Marsh Cone (ASTM C939); water flow time calibrated at 8.0±1.0 sec.
• Strength tests done on standard cubes/beams; average of minimum 3 specimens.
• Mix trials recommended due to variability of materials.

Summary Flowchart for Grout Design

flowchart TD
    A[Select Materials] --> B[Proportion Mix (Cement, Sand, Fly Ash, Micro

Key Formulas & Specifications for Bituminous Mix Design for CGBM (IRC SP 125)

1. Air Voids (Va) and Voids in Mineral Aggregate (VMA)

Using bulk specific gravity of compacted mix (Gmb), theoretical max specific gravity (Gmm), and bulk specific gravity of aggregate (Gsb):

[ \text{Va} = \left(1 - \frac{Gmb}{Gmm}\right) \times 100 ]

[ \text{VMA} = 100 - \left(\frac{Gmb \times P_s}{Gsb}\right) ]

Where:

• (P_s) = % aggregate in mix
• Gmb = Bulk specific gravity of compacted mix
• Gmm = Theoretical maximum specific gravity
• Gsb = Bulk specific gravity of aggregates

2. Aggregate Gradation

• Use CGBM Gr-I, Gr-II, or Gr-III gradations targeting 25-35% air voids.
• Specific gravity of aggregates assumed as 2.7; reduce binder content if higher.

3. Binder Content

• Minimum binder content: 3.25% or as per drain down test.

4. Grout Material Specifications

5. CGBM Composite Requirements

Optimization of Grout for Cement Grouted Bituminous Mix (CGBM) — IRC SP 125

Key Formulas

• Percent Air Voids (Va):
  [ Va = \left(1 - \frac{G_{mb}}{G_{mm}}\right) \times 100 ]

• Voids in Mineral Aggregate (VMA):
  [ VMA = 100 - \frac{G_{mb} \times P_s}{G_{sb}} ]

Where:

• (G_{mb}) = Bulk specific gravity of compacted mix
• (G_{mm}) = Theoretical maximum specific gravity
• (P_s) = Percent aggregate in mix
• (G_{sb}) = Bulk specific gravity of aggregate

Grout Optimization Insights

• Balance grout flow and strength:
  Optimize mixing water content to minimize water while ensuring full grout penetration into bituminous mix voids.
• Marsh Flow Value: Target 20-50 seconds for fluidity (ASTM C939).
• Compressive Strength: 40-100 N/mm² at 28 days (ASTM C109).
• Refer Fig.1 (IRC SP 125) for grout flow vs. water content relationship.

Recommended Specifications (Table 3 Summary)

Key Recommendations for Cement Grouted Bituminous Mix (CGBM) - IRC SP 125

1. Aggregate Gradation & Mix Design (Clause 4.6)

• Aggregate grading: CGBM Gr-I, Gr-II, Gr-III or any grading giving 25-35% air voids.
• Binder content: Minimum 3.25% or as per drain down test.
• Calculate:
  • Percent Air Voids (Va): [ Va = \left(1 - \frac{G_{mb}}{G_{mm}}\right) \times 100 ]
  • Voids in Mineral Aggregate (VMA): [ VMA = 100 - \frac{G_{mb} \times P_s}{G_{sb}} ] where,
  • (G_{mb}) = Bulk specific gravity of compacted mix,
  • (G_{mm}) = Theoretical maximum specific gravity,
  • (P_s) = Percent aggregate,
  • (G_{sb}) = Bulk specific gravity of aggregate.

2. Grout Material (Clause 6, Table 3)

• Cement: OPC 43 or OPC 53 (IS 8112, IS 12269).
• Fly ash: IS 3812 Part 2, min. 65% passing 45 micron.
• Grout properties:
  • Initial setting time: 4-5 hrs (IS 4031 Part 5).
  • Final setting time: 6-10 hrs.
  • Compressive strength (28 days): 40-100 N/mm² (ASTM C109).
  • Flexural strength (28 days): 5-7 N/mm² (IS 4031 Part 8).
  • Fluidity (ASTM C939): 20-50 sec.

3. CGBM Composite Properties (Table 3)

Key Formulas and Specifications for CGBM Production (IRC:SP:125-2019)

1. Job Mix Gradation & Air Voids Calculation (Clause 4.6)

• Bulk Specific Gravity (Gmb): Measured on compacted specimens (ASTM D3203)
• Theoretical Maximum Specific Gravity (Gmm): Measured on uncompacted mix
• Percent Air Voids (Va) and Voids in Mineral Aggregate (VMA) calculated as:

[ \text{Va} = \left(1 - \frac{Gmb}{Gmm}\right) \times 100 ]

[ \text{VMA} = 100 - \frac{Gmb \times P_s}{G_{sb}} ]

Where:

• (P_s) = Percent of aggregate in mix
• (G_{sb}) = Bulk specific gravity of aggregate

2. Optimization of Grout (Clause 5)

• Optimize mixing water content to balance grout flow (Marsh flow value) and strength.
• Maintain full grout penetration into bituminous mix voids for strength.

3. Recommended Properties for CGBM (Table 3)

Key Specifications & Formulas for CGBM (IRC:SP:125-2019)

1. Resilient Modulus (E)

• Lab measured: 12,000 - 15,000 MPa (Indirect Tensile Test ASTM D4123 at 35°C)
• Design value (field conditions): 5,000 MPa (considering aggregate grading variability, grout penetration, and cracks)
• Poisson's ratio (u): 0.25

2. Flexural Strength (Modulus of Rupture, MB)

• Lab measured: 2.5 MPa
• Design value for adequacy check: 1.25 MPa

3. Fatigue Life Equation (IIT Kharagpur, Eq. 4 in IRC SP 125)

• Fatigue life (N) relates to stress and material properties; exact formula not provided in excerpt but typically:

  [ N = k \left(\frac{1}{\sigma}\right)^m ]

  where ( \sigma ) = applied stress, ( k, m ) = material constants (to be obtained from lab fatigue tests).

4. Recommended Properties of CGBM

IRC SP 125: Key Pavement Design Specifications for Cement Grouted Bituminous Mix (CGBM)

1. Mix Design Formulas

• Percent Air Voids (Va):
  [ Va = \left(1 - \frac{G_{mb}}{G_{mm}}\right) \times 100 ]
• Voids in Mineral Aggregate (VMA):
  [ VMA = 100 - \frac{G_{mb} \times P_s}{G_{sb}} ] Where:
  • (G_{mb}) = Bulk specific gravity of compacted mix
  • (G_{mm}) = Theoretical maximum specific gravity
  • (P_s) = Percent aggregate in mix
  • (G_{sb}) = Bulk specific gravity of aggregate

2. Recommended Properties for CGBM (Table Summary)