Tentative Specifications for Stone Matrix Asphalt

IRC SP 79: Introduction - Key Formulas, Tables & Specifications

1. Acceptance Criteria for Tests (Clause 7.5.1)

For density (N≥3) and air voids/VMA (N≥2), the mean value must satisfy:

[ \text{Mean} \geq \text{Specified Value} + \left[1.65 - \frac{1.65}{N^{0.3}}\right] \times \text{Standard Deviation} ]

2. Trial Section (Clause 8)

• Minimum length: 150 m
• Purpose: Validate mixing process, placement, compaction, and surface appearance before main project work.

3. Control Tests & Frequencies (Table 5)

4. Key Formulas

• Voids in Coarse Aggregate (VCA) Dry Rodded:

[ VCA_{DRC} = \frac{(G_{ea} \times Y_w - Y)}{G_{ca} \times Y_w} \times 100 ]

Where:

• (G_{ea}) = Bulk specific gravity of coarse aggregate
• (Y_w) = Unit weight of water (998 kg/m³)
• (Y) = Unit weight of coarse aggregate (

Scope of IRC SP 79 (Stone Matrix Asphalt - SMA):

• Material & Work Quality: Must conform to specified clauses; control tests mandatory during execution.
• Trial Section: Minimum 150 m length off-site to verify mix, compaction, and appearance before main work.
• Control Tests & Frequency: As per Table 5 below.

Table 5: Control Tests & Minimum Frequency for SMA Mix

Key Acceptance Formula (Clause 7.5.1):

[ \bar{X} \geq \text{Specified value} + \left(1.65 - \frac{1.65}{\sqrt{N}}\right) \times \text{Standard Deviation} ]

Where:

• (\bar{X}) = Mean of N samples
• (N) = Number of samples (minimum 2 or 3)

ASTM C29 (Bulk Density of Aggregate) Formula:

[ Y = \frac{G - T}{V} ]

• (Y) = Unit weight of aggregate (kg/m³)
• (G) = Mass of measure + aggregate (kg)
• (T) =

Key Formulas, Tables & Specifications for Materials (IRC SP 79)

1. Mineral Filler (Clause 3.4)

• Consists of finely divided mineral matter (stone dust/hydrated lime).
• Fly ash NOT permitted.
• Grading limits as per Table 2:

2. Coarse Aggregates (Table 1)

*Polishing not required for 19 mm SMA (binder course).

3. Voids in Coarse Aggregate (VCA) Calculation (Clause 4.3)

[ VCA_{DRC} = \frac{(G_{ea} \times Y_w - Y)}{G_{ca} \times Y_w} \times 100 ]

• (VCA_{DRC}): Voids in coarse aggregate (dry rodded)
• (G_{ca}): Bulk specific gravity of coarse aggregate
• (G_{ea}): Bulk specific gravity of effective aggregate (usually)
• (Y_w): Unit weight of water (998 kg/m³)
• (Y): Unit weight of

SMA Mix Design Key Formulas, Tables & Specifications as per IRC SP 79

1. Voids in Coarse Aggregate (VCA) - Clause 4.3

[ VCA_{DRC} = \frac{(G_{ea} \times Y_w - Y)}{G_{ca} \times Y_w} \times 100 ]

• (VCA_{DRC}): Voids in coarse aggregate (dry rodded)
• (G_{ca}): Bulk specific gravity of coarse aggregate
• (Y_w): Unit weight of water = 998 kg/m³
• (Y): Unit weight of coarse aggregate (dry rodded), kg/m³

2. Aggregate Gradation - Table 3 (Typical % Passing by Weight)

3. SMA Mix Requirements - Table 4

• Air void content: 4.0%
• Bitumen content: Minimum 5.8%
• Cellulose fibres: Minimum 0.3% by weight of total mix
• Voids in Mineral Aggregate (VMA): Minimum 17%
• VCA mix: Less than VCA (dry rodded)

4. Quality Control Tests & Frequency - Table 5 Highlights

• Binder quality: Per IS:73 or IRC:SP 53
• Aggregate impact/abrasion: 1 test/50 m³
• Flakiness index: 1 test/50 m³
• Mix grading: 2 tests/day per plant or per 400 tonnes
• Air voids & VMA: 3 tests/400 tonnes, min 2/day per plant
• Density of compacted layer: 1 test/250 m

SMA Production Key Points (IRC SP 79)

1. Fibre Requirements (Clause 3.5.2)

• Contractor must submit fibre manufacturer's test data proving fibre compliance.
• Cellulose fibres must be protected from moisture & contamination before mixing.
• Minimum cellulose fibre content: 0.3% by weight of total mix.

2. SMA Mix Design (Clause 4.3 & Tables 3 & 4)

Aggregate gradation is specified by cumulative % passing various IS sieves (4.75 mm breakpoint).

3. Voids in Coarse Aggregate (VCA) Formula

[ VCA_{DRC} = \frac{(G_{ea} \times \gamma_w - \gamma)}{G_{ca} \times \gamma_w} \times 100 ]

Where:

• ( VCA_{DRC} ) = Voids in coarse aggregate (dry rodded), %
• ( G_{ca} ) = Bulk specific gravity of coarse aggregate
• ( \gamma_w ) = Unit weight of water (998 kg/m³)
• ( \gamma ) = Unit weight of coarse aggregate in dry rodded condition (kg/m³)

4. Indirect Tensile Strength Test (Clause 12.7 & Testing Procedure)

• Specimens compacted to 7.0±0.5% air voids using Marshall compactor.
• Conditioning includes freeze-thaw cycles and moisture saturation.
• Tensile Strength:

[ S_t = \frac{2P}{\pi \times t \times

SMA Placement & Compaction Key Points from IRC SP 79

1. Mix Design & Composition (Clause 4.3, Tables 3 & 4)

• Nominal Aggregate Size: 13 mm (wearing course), 19 mm (binder course)
• Aggregate Gradation: Specified cumulative % passing various IS sieves (see Table 3)
• Mix Requirements:
  • Air voids: 4.0%
  • Bitumen content: ≥ 5.8%
  • Cellulose fibres: ≥ 0.3% by weight
  • Voids in Mineral Aggregate (VMA): ≥ 17%
  • VCA (Mix) < VCA (Dry Rodded)

2. Voids in Coarse Aggregate (VCA) Calculation (Clause 4.3)

[ VCA_{DRE} = \frac{(G_{ea} \times Y_w - Y)}{G_{ca} \times Y_w} \times 100 ]

• (VCA_{DRE}): Voids in dry rodded coarse aggregate (%)
• (G_{ca}): Bulk specific gravity of coarse aggregate
• (Y_w): Unit weight of water (998 kg/m³)
• (Y): Unit weight of dry rodded coarse aggregate (kg/m³)

3. Fibre Addition (Clause 5.3)

• Add cellulose fibres (0.3% min.) dry into weigh hopper or via separate feeding system.
• Increase dry mixing time by 5-10 sec; wet mixing by at least 5 sec.
• No fibre dust allowed in baghouse emissions.

4. Placement & Compaction (Clause 6 & 7.5.1)

• Trial sections (min. 150 m) to verify mix and compaction.
• Acceptance criteria for density and air voids based on mean ± statistical tolerance.
• Density test frequency: 1 per 250 m².
• Control tests include binder quality, aggregate tests, mix grading, air voids, VMA, and temperature monitoring.

5. Quality Control Tests (Table 5)

• Frequent testing of binder, aggregate properties, mix gradation, air voids, and compaction.
• Temperature of binder and aggregate monitored regularly during laying.

Summary Flow of SMA Placement &

IRC SP 79: Controls for Stone Matrix Asphalt (SMA)

Key Control Tests & Frequencies (Table 5)

Acceptance Criteria (Clause 7.5.1)

[ \text{Mean} \geq \text{Specified value} + \left[1.65 - \frac{1.65}{\sqrt{N}}\right] \times \text{Standard deviation} ]

• (N) = number of samples (min 2 or 3 depending on test)

Important Formulas

Voids in Coarse Aggregate (Dry Rodded) - VCA: [ VCA_{DRC} = \frac{(G_{ea} \times Y_w - Y)}{G_{ca} \times Y_w} \times 100 ]

• (G_{ca}) = Bulk specific gravity of coarse aggregate
• (Y_w) = Unit weight of water (998 kg/m³)
• (Y) = Dry rodded unit weight (kg/m³)

SMA Mix Requirements (Table 4)

IRC SP 79: Trial/Experimental Section Key Points

1. Trial Section Requirements (Clause 8)

• Minimum length: 150 m
• Purpose: Verify mixing plant control, job mix formula tolerances, placement, SMA surface, and compaction.
• Main work starts only after satisfactory test results on mix composition, gradation, volumetrics.

2. Acceptance Criteria (Clause 7.5.1)

• For density (N≥3) and air voids/VMA (N≥2):

  [ \text{Mean} \geq \text{Specified Value} + \left[1.65 - \frac{1.65}{N^{0.3}}\right] \times \text{Standard Deviation} ]

3. Control Tests & Frequency (Table 5)

4. Important Test Methods Referenced

• ASTM C29: Bulk density and voids in aggregate (dry rodded)
• ASTM D2041: Theoretical maximum specific gravity (Gmm) of bituminous mixtures
• Indirect Tensile Strength Test: For moisture damage resistance (TSR calculation)

5. Tensile Strength Ratio (TSR)

[ TSR = \frac{S_2}{S_1} \times 100% ]

• (S_1) = avg tensile strength (dry)
• (S_2

ASTM C29 - Bulk Density and Voids in Aggregate (Outline from IRC SP 79 Annex A)

Key Formulas:

• Dry Rodded Unit Weight (Y):
  [ Y = \frac{G - T}{V} ] Where:

  • ( G ) = mass of measure + aggregate (kg)
  • ( T ) = mass of empty measure (kg)
  • ( V ) = volume of measure (m³)

• Voids in Coarse Aggregate (VCA dry rodded):
  [ VCA_{DRC} = \left(\frac{G_{ea} \times Y_w - Y}{G_{ca} \times Y_w}\right) \times 100 ] Where:

  • ( G_{ca} ) = bulk specific gravity of coarse aggregate
  • ( G_{ea} ) = bulk specific gravity of coarse aggregate fraction
  • ( Y_w ) = unit weight of water (998 kg/m³)
  • ( Y ) = dry rodded unit weight (kg/m³)

Specifications & Equipment:

• Measure: Cylindrical metal, ~10 L capacity, height ≈ diameter
• Tamping rod: 16 mm diameter, 600 mm length, hemispherical tip
• Balance: Accuracy ±0.1% of load
• Plate glass: To level water surface during volume calibration

Testing Procedure Summary:

1. Calibrate measure volume using water and plate glass.
2. Fill measure with aggregate using dry rodding method (tamping rod).
3. Weigh measure + aggregate and measure alone.
4. Calculate dry rodded unit weight and voids.

SMA Mix Design Voids (Clause 4.3 & 4.6):

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

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

• **Voids in Coarse Aggregate in Mix (VCAm

ASTM D 2041 - Theoretical Maximum Specific Gravity (Gmm) and Density of Bituminous Mixtures

Purpose:
Determines theoretical maximum specific gravity (Gmm) of loose bituminous mixtures at 25°C for calculating air voids, absorbed binder, and compaction targets.

Key Equipment

• Vacuum container (metal/plastic bowl or volumetric flask, ~4 L capacity)
• Vacuum pump with pressure gauge (target vacuum: 3.7 ± 0.3 kPa)
• Water bath at 25 ± 1°C
• Balance accurate to 0.1%

Procedure Outline

1. Sample Preparation: Place loose mix in vacuum container; add water at 25°C.
2. Vacuum Application: Apply vacuum gradually to remove entrapped air for 15 ± 2 min at 3.7 ± 0.3 kPa.
3. Weighing:
   • Underwater weighing (mass of bowl, sample in water) or
   • Air weighing (mass of bowl, sample, and water filled container)
4. Calculate Gmm:

Method	Formula	Variables
Underwater (Bowl)		A = dry sample mass (g) <br> B = bowl mass under water (g) <br> C = bowl + sample mass under water (g)
Air (Bowl/Flask)		A = dry sample mass (g) <br> D = lid + container + water mass (g) <br> E = lid + container + sample + water mass (g)

Acceptance Criteria (Clause 7.5.1)

• Mean of N samples ≥ specified value + [

Outline of ASTM D 6390 – Draindown Characteristics (per IRC:SP:79 Annex C)

Scope

• Measures binder draindown from uncompacted asphalt mixtures at elevated temperatures (120–175°C).
• Applicable for open-graded and gap-graded mixes like SMA.

Equipment

• Forced draft oven (±2°C control).
• Wire basket (6.3 mm sieve cloth, ±10% dimension tolerance).
• Catch plate.
• Balance (accuracy 0.1 g).

Test Procedure

1. Weigh empty wire basket: Mass A.
2. Place 1200 ± 200 g hot mix loosely in basket, weigh basket + mix: Mass B.
3. Weigh empty catch plate: Mass C.
4. Hang basket in oven at test temperature for 1 hour ± 5 min.
5. Remove basket and plate, cool, weigh catch plate + drained material: Mass D.

Calculation

[ \text{Draindown (%)} = \frac{(D - C)}{(B - A)} \times 100 ]

• Average two replicates at production temperature and at +10°C.
• Maximum allowed draindown: 0.30% (adjust fibre content if exceeded).

Wire Basket Assembly (Figure 1)

• Standard wire basket made from 6.3 mm sieve cloth.
• Dimensions ±10% per IRC:SP:79.

Additional Notes

• Draindown test must be performed at anticipated plant production temperature and 10°C above.
• Use pelletized cellulose fibers ≥ 0.3% by weight to control draindown.

flowchart TD
    A[Weigh empty wire basket (Mass A)] --> B[Add 1200±200g hot mix, weigh basket+mix (Mass B)]
    B --> C[Weigh empty catch plate (Mass C)]
    C --> D[Hang basket in oven at test temp for 1 hr]
    D --> E[Remove basket & plate, cool]
    E --> F[Weigh catch plate + drained material (Mass D)]
    F --> G[Calculate Draindown % = ((D-C)/(B-A))*100]

This test ensures asphalt mixtures meet draindown limits to avoid binder loss during handling and placement.

Schellenberg Binder Drainage Test (IRC:SP:79 Annex D)

This test measures binder draindown in SMA mixes at elevated temperatures.

Key Steps & Formula:

Binder Draindown Calculation:

[ \text{Binder Draindown (%)} = \frac{(C - A)}{(B - A)} \times 100 ]

• A = Mass of empty beaker (g)
• B = Mass of beaker + SMA mix (g)
• C = Mass of beaker after draining (g)

Specifications:

• Max allowable draindown: 0.30%
• Test temperature: 170℃ ±1℃ for 1 hour
• Use glass/tin cover during heating
• No shaking/vibration while emptying beaker

Additional Notes:

• If draindown exceeds 0.3%, increase cellulose fiber content (min 0.3% by weight) to reduce draindown.
• Test at anticipated plant mixing temperature for accuracy.

Diagram: Schellenberg Test Setup

flowchart TD
    A[Weigh Empty Beaker (A)] --> B[Add ~1kg SMA Mix, Weigh (B)]
    B --> C[Cover & Heat at 170℃ for 1 hour]
    C --> D[Remove & Empty Beaker (No Shaking)]
    D --> E[Weigh Empty Beaker (C)]
    E --> F[Calculate Draindown %]

This test ensures SMA mix stability during production and placement by controlling binder drainage.

Key References, Formulas, and Tables from IRC SP 79 for SMA Mix Design and Testing

1. Acceptance Criteria for Tests (Clause 7.5.1)

[ \text{Mean} \geq \text{Specified Value} + \left[1.65 - \frac{1.65}{N^{0.3}}\right] \times \text{Standard Deviation} ]

• (N) = number of samples (min. 3 for density, min. 2 for air voids & VMA)

2. Control Tests Frequency (Table 5)

3. Voids in Coarse Aggregate (VCA) - Clause 4.3

[ VCA_{DRC} = \frac{(G_{ea} \times Y_w - Y)}{G_{ca} \times Y_w} \times 100 ]

• (VCA_{DRC}): Voids in coarse aggregate (dry rodded)
• (G_{ca}): Bulk specific gravity of coarse aggregate
• (Y_w): Unit