Case Study: Road Rehabilitation Using Geotextile Interlayers

The Challenge:

An aging highway was experiencing severe cracking. The old asphalt was breaking up, and water was infiltrating the subgrade, causing potholes and weakening the foundation. Simply paving over the old road (a thick overlay) would be expensive and would only delay the inevitable.

The Solution:

Engineers specified a paving-grade geotextile interlayer (a type of stress-absorbing membrane interlayer - SAMI).

1. The old pavement was milled and leveled.
2. A bituminous emulsion tack coat was applied.
3. The geotextile was rolled out and pressed into the tack coat.
4. New asphalt was laid on top.

The Mechanism:

The geotextile acted as a waterproofing membrane, sealing the old pavement and preventing water ingress. More importantly, it acted as a stress distributor. When the old pavement cracked or moved due to temperature changes, the flexible geotextile absorbed the energy, preventing it from traveling up into the new asphalt layer (reflective cracking).

The Results:

• Cost Savings:The project used less new asphalt than a traditional thick overlay.
• Extended Lifespan:The new pavement showed significantly fewer cracks in the first year compared to similar sections without the interlayer.
• Faster Construction:The geotextile installation was quick, minimizing traffic disruption.

Conclusion

This case study demonstrates that geotextiles are not just for new construction. They are powerful tools for extending the life of existing infrastructure, offering a smart return on investment for cash-strapped municipalities.