what are the recommendation listed about flexible and rigid pavement on ERA manual?

The ERA manual provides the following recommendations for flexible and rigid pavements:

1. Flexible Pavements:
- Use flexible pavements for low to medium traffic volumes and where the subgrade is stable.
- Consider using asphalt concrete as the surface layer for flexible pavements.
- Ensure proper drainage to prevent water infiltration and damage to the pavement structure.
- Regularly inspect and maintain flexible pavements to prevent deterioration and prolong their service life.

2. Rigid Pavements:
- Use rigid pavements for high traffic volumes and where the subgrade is weak or unstable.
- Consider using concrete as the surface layer for rigid pavements.
- Provide proper jointing and reinforcement to control cracking in rigid pavements.
- Regularly inspect and maintain rigid pavements to prevent joint deterioration and maintain ride quality.

Overall, the ERA manual recommends selecting the appropriate pavement type based on traffic volume, subgrade conditions, and maintenance requirements to ensure long-term performance and durability.

Flexible Pavement Recommendations:

- Base Course:
- Use crushed aggregate with a maximum aggregate size of 50 mm (2 in) or smaller.
- Target a minimum layer thickness of 150 mm (6 in).
- Subbase Course:
- Use crushed aggregate, gravel, or soil-aggregate with a maximum aggregate size of 75 mm (3 in) or smaller.
- Target a minimum layer thickness of 200 mm (8 in).
- Asphalt Concrete Surface:
- Use a minimum binder course thickness of 50 mm (2 in) and a minimum surface course thickness of 25 mm (1 in).
- Consider using a thick asphalt overlay if expected traffic loads exceed design criteria.

Rigid Pavement Recommendations:

- Concrete Base:
- Use Portland cement concrete with a minimum compressive strength of 30 MPa (4350 psi).
- Target a minimum pavement thickness of 200 mm (8 in) for highways and 150 mm (6 in) for roads.
- Joints:
- Use contraction joints spaced at 5-10 m (16.4-32.8 ft) intervals.
- Consider using expansion joints at locations where significant movement is expected, such as bridge abutments or intersections.
- Reinforcement:
- Reinforce the concrete base with steel bars or fibers to improve flexural strength and reduce cracking.
- Surface Treatment:
- Apply a surface treatment or overlay to enhance skid resistance and durability.