Bangkok Road Rehabilitation – Case Study

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Project

In 1999, the Bangkok Metropolitan Authority reconstructed the iconic Ratchadamnoen Klang Road. The total area for the road rehabilitation project covered 8,000 m2. The pavement was constructed over a 30-day period during November 1999.

Design and Construction

The degraded asphalt pavement was demolished and stockpiled. The in-situ soil (very soft clay) was excavated to the required depth. The stockpiled old asphalt pavement material was recycled as the new sub-base and compacted to a depth of 150mm.

A new 300mm base layer was constructed from crushed rock stabilised with cement and Renolith. The crushed rock, cement and water were combined at a mixing plant and transported to site via ready-mixed concrete truck. Renolith admixture was added to mix at site.  The base material was laid and compacted. The mix design for the base layer was:

  • Cement at 5% w/w of crushed rock
  • Renolith (original formula) at 10% w/w of cement
  • Water at 5% w/w of crushed rock

An asphalt wearing surface was applied to a depth of 50mm.

Major plant for this project consisted of a back-hoe, grader, roller compactor and ready-mixed concrete truck.

The total cost was 3,200,000 Baht (400 Baht per sqm) – roughly $140,000 AUD (or AUD$17 per sqm) in 1999. This equates to approximately AUD$34 per sqm in 2024 when adjusted for inflation

Rachadamnoen Klang Road rehabilitation 1999

Ratchadamnoen Klang Road, Bangkok – 1999

Review - 2024

Using Google Earth – street view it is possible to inspect the current state of the pavement. The road appears to be in very good condition a quarter of a century later.

Rachadamnoen Klang Road 2023
Rachadamnoen Klang Road, Bangkok – 2023 (Google Earth view)
Rachadamnoen Klang Road 2023c

The project was very successful in all key aspects:

  • Construction cost. At approx AUD$34 per sqm (2024 inflation adjusted), the construction cost was much lower than alternates such as unbound granular or concrete pavement.
  • Environment / Carbon footprint. The project recycled the old pavement material, minimising the carbon cost. The pavement was thinner in comparison to a typical unbound granular design, thereby much less material was consumed. Compared to a typical concrete pavement, the project used less cement and no steel, with a commensurate lower carbon footprint.
  • Resilience / Whole-of-life cost. Excellent. No apparent degradation after 25 years. The design was quite conservative in comparison to modern best practice. The 300mm base layer of Renolith-enhanced cemented crushed rock would yield an extremely high fatigue life, if designed/assessed against Austroads Guide to Pavement Technology Part 2: Pavement Structural Design. With such a high traffic capacity and the inherent stability (water resistant, chemical resistant) of Renolith-enhanced cemented materials, it is conceivable that this road could last for centuries.
Conclusion

Crushed rock was stabilised with Renolith and cement to form the base layer for the Ratchadamnoen Klang Road. The construction process was fast, low-cost and low-carbon. The pavement remains in very good condition after more than 25 years – a truly sustainable outcome.

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