Tentative Specifications for Slurry Seal and Microsurfacing

Scope Summary from IRC SP 81 (Slurry Seal and Microsurfacing):

• Materials: Aggregates must meet properties in Table 2 (e.g., Sand Equivalent ≥ 50, Water Absorption ≤ 2%, Soundness limits). Water absorption up to 4% allowed if soundness and wet stripping pass.

• Aggregate Grading: Table 3 specifies gradation for three types:

  • Type I: 2-3 mm
  • Type II: 4-6 mm
  • Type III: 6-8 mm

• Mix Design: Table 4 defines slurry seal mix criteria:

  Parameter	Spec	Test Method
  Mix Time (min)	≥ 180 s	Appendix-1
  Consistency (max)	3 cm	Appendix-3
  Wet Cohesion (min)	20 kg.cm	Appendix-4
  Wet Stripping (min pass)	90%	Appendix-5
  Wet Track Abrasion (max)	800 g/m²	Appendix-6

• Ingredient Limits (by dry aggregate weight): Table 5

  • Bitumen Emulsion: 6.5–16% (varies by type)
  • Water: 6–12%
  • Filler (OPC): 0.5–2%
  • Additive: 0.5–2%

• Bitumen Emulsion Requirements (Microsurfacing): Table 8

  • Residue on 600 µm sieve ≤ 0.05%
  • Viscosity: 20–100 s (Saybolt Furol at 25°C)
  • Residue Penetration: 40–100 (IS 1203)
  • Softening Point ≥ 57°C
  • Elastic Recovery ≥ 50%

Key Notes:

• Filler: Ordinary Portland Cement preferred.
• Water: Potable, pH 6-7.
• Additives: Used to control set time and improve surface; compatibility with emulsion mandatory.
• Trial Mix: Required to verify breaking and setting time on site.

flowchart TD
    A[Aggregate Selection] --> B[Mix Design]
   

IRC SP 81: Application Limitations & Key Specifications

1. Aggregate Properties (Clause 6.5, Table 2)

Water absorption between 2-4% allowed if soundness & wet stripping tests pass.

2. Grading of Aggregates (Table 3)

*Tolerances (Clause 4.75): ±5% for 600μm–4.75mm, ±4% for 300μm, ±3% for 150μm, ±2% for 75

Slurry Seal - IRC SP 81 Key Specifications & Formulas

1. Materials Proportion (by weight of dry aggregates)

2. Mix Design Criteria (Table 4)

3. Construction Highlights

• Temperature: Do not apply if pavement or air temperature < 10°C.
• Surface Prep: Clean thoroughly; pre-treat cracks.
• Tack Coat: Usually not required; if needed, use diluted RS-1 emulsion at 0.2 kg/m².
• Application: Use calibrated self-propelled slurry seal machine.
• Setting Time: Max 4 hours before opening to traffic.
• Traffic Speed: Limit to 20 km/h for 12 hours post-application.

4. Quality Control Testing Frequency (Table 6)

5. Important Notes

• Water: Potable

Here is a concise summary of key formulas, tables, and specifications for Construction from IRC SP 81 related to microsurfacing and slurry seal mixes:

1. Aggregate Properties (Table 2)

2. Aggregate Grading (Table 3)

3. Mix Design Criteria

Microsurfacing Mix (Table 9)

IRC SP 81: Microsurfacing Key Specifications & Formulas

1. Microsurfacing Composition

• Modified bitumen emulsion (polymer/rubber latex)
• Mineral aggregate (Type II or III grading)
• Water & additives (if needed)

2. Types & Application (Table 7)

3. Mix Design Criteria (Table 9)

4. Indicative Mix Ingredients (Table 10)

5. Application & Quality Control

• Use calibrated microsurfacing machine with twin-shaft paddles/augers.
• Uniform spread and homogenous mix mandatory.
• Rolling generally not required; if needed, pneumatic roller with **0.75

Here is a concise summary of key formulas, tables, and specifications from IRC SP 81 for microsurfacing and slurry seal materials:

1. Aggregates Properties (Table 2)

*Water absorption 2-4% allowed if soundness & wet stripping pass.

2. Aggregate Grading (Table 3)

*Type I not suitable for microsurfacing.

3. Modified Bitumen Emulsion for Microsurfacing (Table 8)

IRC SP 81: Appendix-1 — Method for Determination of Mixing Time of Slurry Seal/Microsurfacing Mixture

Scope

• Determine breaking time of emulsion in slurry seal/microsurfacing mix.

Apparatus

• Stainless steel bowl, spatula, beakers, measuring cylinders, spoon, balance.

Procedure

1. Take 1 kg graded aggregate + required cement in bowl.
2. Add mixing water with additive (if any) and mix vigorously to form homogeneous paste.
3. Add required emulsion quantity, mix continuously with spatula.
4. Observe color change from brown to blackish brown indicating emulsion breaking.
5. Record time taken for breaking — this is Mixing Time.

Reporting

• Report Maximum Mixing Time (minimum required:
  • Slurry Seal: 180 seconds (Table 4)
  • Microsurfacing: 120 seconds (Table 9))

Key Tables Summary

Indicative Mix Proportions (By weight of dry aggregate)

Notes

• Mixing time is critical for workability and proper setting.
• Add

IRC SP 81 - Appendix 2: Determination of Set Time of Slurry Seal/Microsurfacing Mixture

Scope:

• To determine the initial set time of slurry seal or microsurfacing mix.

Apparatus:

• Bitumen Felt Pad: 152 mm x 152 mm (13.6 kg Roofing Felt)
• White Paper Towel or Tissue

Procedure:

• Place a sample of slurry seal/microsurfacing mixture on the felt pad.
• Observe the time until the mixture no longer leaves a stain on the felt (stain-free blot).
• This time is recorded as the Minimum Set Time.

Key Specifications:

• Maximum Set Time: 2 hours (traffic can be opened after 2 hours at 20 km/h speed).
• Mix Time (Appendix-1): Minimum 180 seconds.
• Consistency (Appendix-3): Maximum 3 cm flow.
• Wet Cohesion (Appendix-4): Minimum 20 kg.cm within 60 minutes.

Indicative Mix Proportions (by weight of dry aggregate):

Summary Flowchart of Set Time Test:

flowchart TD
    A[Prepare slurry seal/microsurfacing mix] --> B[Place sample on bitumen felt pad]
    B --> C[Observe stain on felt pad]
    C --> D{Is blot stain-free?}
    D -- No --> C
    D -- Yes --> E[Record time as Minimum Set Time]

References: ASTM D 3910, ISSA TB 139, MS 19 Asphalt Emulsion Manual.

This method ensures the slurry seal/microsurfacing mix sets within the specified time for safe traffic opening and durability.

Appendix-3: Determination of Consistency of Slurry Seal/Microsurfacing Mixture (IRC SP 81)

Apparatus

• Metal mould (frustum cone):
  • Top diameter = 38 mm
  • Base diameter = 89 mm
  • Height = 76 mm
• Metal plate (228 mm diameter) with concentric inscribed circles:
  • Center circle diameter = 89 mm
  • Additional circles: each 13 mm larger than the previous

Test Method

1. Loosely fill the mould with slurry seal/microsurfacing mix and strike off excess.
2. Invert the mould with contents onto the metal plate’s center circle.
3. Quickly invert mould and plate together, remove mould.
4. Allow slurry to flow over inscribed circles until flow stops.
5. Measure outflow diameter at four points, 90° apart.

Reporting

• Consistency = Average outflow diameter (cm)
• Maximum allowed consistency: 3 cm (Table 4)

Summary Table

Notes

• Consistency indicates workability and flow characteristics.
• Ensures proper mix for placement without segregation or excessive flow.
• Used alongside other tests: Mixing Time (Appx-1), Set Time (Appx-2), Wet Cohesion (Appx-4).

flowchart LR
    A[Mould filled with slurry] --> B[Invert onto metal plate]
    B --> C[Invert mould & plate together]
    C --> D[Remove mould]
    D --> E[Slurry flows over circles]
    E --> F[Measure flow diameter at 4 points]
    F --> G[Calculate average consistency]

This method ensures the slurry mix has suitable consistency for field application per IRC SP 81.

IRC SP 81 - Appendix 4: Cure Time Determination for Slurry Seal/Microsurfacing Mixture

Key Specifications & Procedure

• Apparatus:

  • Bitumen felt pad (152 mm × 152 mm, 13.6 kg roofing felt)
  • White paper towel or tissue for blot test.

• Definition:

  • Minimum Set Time: Time to obtain a stain-free blot on bitumen felt pad after placing slurry seal/microsurfacing mix.

• Test Method (Clause 25.4):

  1. Cast uniform specimens in 6 mm or 10 mm ring mould on bitumen roofing felt.
  2. Use a pneumatically actuated rubber foot (25.4 mm dia.) of calibrated cohesion tester applying 193 kPa pressure (simulates tyre pressure).
  3. Measure torque at intervals: 30, 45, 60, 75, 90, 120, 180, 240 min after casting.
  4. Cure Time = Time when maximum stable torque is reached or rubber foot moves freely without dislodging aggregates.

• Torque Criteria:

  System Type	Torque (kg.cm)	Time Limit (min)
  Quick Traffic	20-21	≤ 60
  Quick Set	12-13	≤ 30

• Traffic Opening:

  • Microsurfacing requires ~2 hours to set.
  • Traffic allowed at 20 km/h after 2 hours, normal speed after 12 hours.

Relevant Tables Summary

Indicative Mix Ingredient Limits (% by

Appendix-5: Wet Stripping of Cured Slurry Seal Mix (IRC SP 81)

Objective

• To evaluate the compatibility of slurry seal/microsurfacing system with aggregate by testing the retention of bitumen coating after boiling in water.

Apparatus

• 600 ml beaker
• Hot plate with temperature control
• Absorbent high wet strength paper

Procedure

1. Boil 400 ml of demineralized/distilled water in a 600 ml beaker.
2. Drop 10 gm of cured slurry seal mix into boiling water for 3 minutes.
3. Remove beaker, cool to room temperature.
4. Rinse with cold tap water until free bitumen flows over beaker edge.
5. Decant water, place sample on absorbent paper to dry.
6. Examine for uncoated aggregate areas.

Reporting Criteria

Key Related Specifications (Table 4: Mix Design Criteria)

Indicative Mix Proportions (per dry aggregate weight)

Summary Diagram: Wet Stripping Test Procedure

flowchart TD
    A[Prepare 10 gm cured slurry sample

Appendix-6: Wet Track Abrasion Test (IRC SP 81)

Objective

• Determine abrasion resistance of slurry seal/microsurfacing.
• Establish minimum permissible bitumen emulsion content.

Apparatus

• Balance (±1 g accuracy, up to 5000 g)
• Planetary mechanical stirrer with weighted rubber hose
• Flat bottom metal pan (Ø330 mm, 51 mm height) with clamps
• Heavy gauge round-bottom bowl
• Long-handled serving spoon (≥101 mm projection)
• Circular metal disks (Ø286 mm, thickness 6 & 8 mm)
• Oven (60 ± 3°C)
• Water bath (25 ± 1°C)

Sample Preparation

1. Oven dry aggregates at 105-110°C for ~16 hrs to constant weight.
2. Mix predetermined quantities of aggregates, filler, water, additives, and bitumen emulsion.
3. Pour mix into mould on felt disc; screed and remove excess.
4. Oven dry specimen at 60°C for 24 hrs; cool and weigh.

Test Procedure

• Clamp specimen in pan; cover with 6 mm water at 25°C.
• Attach rubber hose abrasion head to stirrer shaft.
• Operate at low speed for 5 minutes, abrading specimen.
• Wash specimen, dry at 60°C to constant weight.
• Calculate Wear Value (WTAT loss) as weight loss per m².

Report

• WTAT loss in grams per square meter (g/m²).

Key Formula

[ \text{WTAT Loss} = \frac{\text{Initial Weight} - \text{Final Weight}}{\text{Surface Area (m}^2)} \quad [g/m^2] ]

Summary Flowchart

flowchart TD
  A[Dry Aggregates] --> B[Mix with Water, Additives, Bitumen Emulsion]
  B --> C[Cast Specimen in Mould on Felt Disc]
  C --> D[Oven Dry at 60°C for 24 hrs]
  D --> E[Clamp Specimen in Pan with Water]
  E --> F[Operate Abrasion Head for 5 min]
  F --> G[Wash & Oven Dry Specimen]
  G --> H[Calculate WTAT Loss]
  H --> I[Report Wear Value (g/m²)]
``

IRC SP 81 – Appendix 7: Calibration of Slurry Seal/Microsurfacing Machine

Key Specifications & Procedure:

• Purpose: Ensure accurate metering of aggregate, bitumen emulsion, cement, water, and additives.
• Calibration Sequence:
  1. Calibrate aggregate feed first (base for other ingredients).
  2. Adjust bitumen emulsion flow next.
  3. Calibrate cement, then water, and additives.
• Metering: Continuous feed with counters measuring weight/time at various settings.
• Output: Weight per minute for each ingredient at different settings.
• Documentation: Flow chart of outflows for future reference.
• Quality Control: Periodic checks during construction to maintain mix consistency.

Important Notes:

• Calibration must be done prior to construction.
• Accurate calibration avoids mix inconsistency affecting performance.
• Machine settings recorded by both contractor and client.
• Calibration ensures mix proportions match the approved job mix formula.

Summary Table for Calibration Steps:

flowchart TD
    A[Start Calibration] --> B[Calibrate Aggregate Feed]
    B --> C[Adjust Bitumen Emulsion Flow]
    C --> D[Adjust Cement Flow]
    D --> E[Adjust Water Flow]
    E --> F[Adjust Additives Flow]
    F --> G[Record Settings & Flow Rates]
    G --> H[Periodic Quality Checks]

This ensures precise mix proportions, critical for slurry seal/microsurfacing quality and durability.

IRC SP 81 - Appendix-8: Test Method for Torsional Elastic Recovery of Residual Binders

Apparatus:

• Bolt assembly:
  • Cylindrical head diameter = 28.6 mm, thickness = 9.52 mm
  • Threaded shank length = 44.5 mm
• Metal spider with 3 radial pins and 2 nuts (for centering) or pointer for angle measurement
• Sample tin: capacity 85 ml, diameter 51-52 mm
• Angle measuring device with scale radius 80 mm, graduated in degrees
• Clamp: holds sample cup within 3 mm of center, deformation < 3 mm
• Water bath at 25±1℃
• Forced convection oven (60-200℃)
• Stopwatch, spanner

Sample Preparation & Test Procedure:

1. Pour residue into cup until meniscus forms on bolt top.
2. Cool 1 hour at room temperature; adjust bolt flush with sample surface.
3. Place in 25℃ water bath for 1 hour.
4. Adjust spider 7 mm above rim; fit pointer at 180°.
5. Twist bolt steadily from 180° to 0° over 10 seconds using spanner.
6. Release bolt; start timing.
7. Measure recovered angle A after 30 seconds.

Calculation:

[ \text{Torsional Elastic Recovery (%)} = \frac{A}{180} \times 100 ]

Where:

• A = recovered angle (degrees) after 30 s

Reporting:

• Average of three tests
• Include test temperature and recovery time

flowchart TD
    A[Pour residue in cup] --> B[Cool 1 hr at room temp]
    B --> C[Water bath @ 25℃ for 1 hr]
    C --> D[Set pointer at 180°]
    D --> E[Twist bolt 180° to 0° in 10s]
    E --> F[Release bolt & start timer]
    F --> G[Measure recovered angle after 30s]
    G --> H[Calculate % recovery = (A/180)*100]
    H --> I[Report average of 3 tests]

This method evaluates the elastic recovery