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Remove damaged asphalt binder course layer by milling machine.
09/10/2025

Remove damaged asphalt binder course layer by milling machine.

Box Paver Calibration for Subbase Course Construction?Calibrating a box paver machine ensures accurate and uniform place...
08/29/2025

Box Paver Calibration for Subbase Course Construction?

Calibrating a box paver machine ensures accurate and uniform placement of the subbase layer during road construction. Below is a concise method for calibration:

1. Pre-Calibration Checks:
- Inspect the box paver for mechanical issues (e.g., screed, conveyor, hopper, and sensors).
- Verify that the machine is on a stable, level surface.
- Confirm that approved subbase material is available for testing.

2. Screed Adjustment:
- Set the screed to the desired thickness of the subbase layer (e.g., 150-300 mm, as per design).
- Adjust the screed angle (angle of attack) to achieve the correct surface slope and crossfall, using manual controls or automatic grade/slope sensors.

3. Sensor and Control Calibration:
- Calibrate automatic leveling systems (e.g., laser or stringline sensors) to match the design alignment and grade.
- Test sensor accuracy by running the paver over a short test section and checking the laid material’s thickness and slope with a leveling rod or survey equipment.

4. Material Flow Calibration:
- Load a known quantity of subbase material into the hopper.
- Run the paver at a consistent speed to spread material over a measured test area.
- Measure the thickness and width of the laid material to confirm uniformity and compare with design specifications.
- Adjust the flow gates or auger speed to control material distribution if inconsistencies are found.

5. Compaction and Surface Verification:
- Compact the test section and measure the density to ensure it meets project requirements (e.g., 95-98% of maximum dry density).
- Check surface smoothness and alignment using a straightedge or survey tools, ensuring tolerances are met.

6. Final Adjustments:
- Fine-tune screed settings, sensor alignment, or material flow based on test results.
- Repeat test runs until the paver consistently produces the specified layer thickness, slope, and uniformity.

7. Documentation:
- Record calibration settings, test measurements, and any adjustments made.
- Obtain engineer approval before full-scale paving begins.

Notes:
- Perform calibration at the start of the project or when changing material types or layer thicknesses.
- Regularly check calibration during operations to maintain accuracy, especially after maintenance or prolonged use.
- Ensure operators are trained and follow safety protocols during calibration.

This process ensures the box paver delivers a uniform and compliant subbase layer, critical for road durability and performance.

Asphalt Concrete paving.
08/17/2025

Asphalt Concrete paving.

Skid Resistance in Road ConstructionSkid resistance refers to the frictional force between a vehicle’s tires and the roa...
07/16/2025

Skid Resistance in Road Construction

Skid resistance refers to the frictional force between a vehicle’s tires and the road surface, which helps prevent skidding or loss of traction, especially during braking, accelerating, or cornering. It is a critical function of the wearing course layer in road construction, ensuring safety and control for vehicles, particularly in wet or adverse conditions.

# # # Key Aspects of Skid Resistance:
1. Surface Texture:
- Macrotexture: The coarse texture formed by the arrangement of aggregate particles in the wearing course. It allows water to drain from the tire-road contact area, reducing hydroplaning in wet conditions. Measured in terms of texture depth (e.g., sand patch test).
- Microtexture: The fine-scale roughness of individual aggregate surfaces. It provides grip by creating friction at the tire-surface interface, especially at low speeds.

2. Factors Influencing Skid Resistance:
- Aggregate Properties: Aggregates with high polish resistance (e.g., angular, hard stones like granite) maintain microtexture longer, ensuring sustained friction.
- Asphalt Mix Design: Open-graded friction courses (OGFC) or stone mastic asphalt (SMA) enhance macrotexture for better water drainage and grip.
- Surface Condition: Wet, oily, or debris-covered surfaces reduce skid resistance. Regular cleaning and maintenance are essential.
- Traffic Wear: Over time, aggregates may polish under traffic, reducing microtexture and skid resistance.
- Weather: Wet or icy conditions lower friction, making high skid resistance critical.

3. Measurement:
- Skid resistance is quantified using devices like the Pendulum Skid Resistance Tester or the Dynamic Friction Tester, often expressed as a Skid Number (SN) or Friction Coefficient.
- Higher values indicate better skid resistance (e.g., SN ≥ 40 is typically desirable for high-traffic roads).

4. Importance in Safety:
- Prevents skidding accidents, especially on curves, intersections, or slopes.
- Enhances braking efficiency, reducing stopping distances.
- Improves vehicle handling in adverse weather, such as rain or snow.

5. Design Considerations:
- Select aggregates with high polish stone value (PSV) for durability and friction.
- Use mix designs like OGFC or SMA for enhanced texture and drainage.
- Ensure proper construction techniques (e.g., uniform compaction) to maintain surface texture.
- Regular maintenance, such as resurfacing or applying surface treatments, to restore skid resistance over time.

By optimizing skid resistance, the wearing course enhances road safety, reduces accident risks, and ensures reliable vehicle performance under various conditions.

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