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Project
In 1997, the Bangkok Metropolitan Authority initiated the Bicycle Track Project along Ekkamai-Ram Inthra Road. The project aimed to promote eco-friendly commuting and enhance the overall urban experience.
Project Description
The total area for the combined footpath and bicycle track covered 60,000 m2, with a width of 2.5 meters and 24 km in length. The track was constructed over a 20-day period during November 1997. The total cost of the project was 10,000,000 Baht (approximately $450,000 AUD in 1997), equating to 167 Baht per sqm (approximately AUD$7.50 in 1997, equivalent to AUD$15 per sqm in 2023 when adjusted for inflation).
Design and Construction
The in-situ silty-sand soil was used as the base material. No additional fill was required. The in-situ soil was stabilised with cement and Renolith to a depth of 70mm. An asphalt wearing surface was applied to a depth of 30mm. The mix design for the Renolith base layer was:
- Cement at 5% w/w of in-situ soil
- Renolith (original formula) at 5% w/w of cement
- Water at 10% w/w of in-situ soil
Major plant for this project consisted of a grader, water truck and roller.
Construction Process
- Clear. The construction site was cleared. Organic material such as leaves, grass and roots were removed.
- Pulverise. The in-situ soil was pulverised, then shaped and trimmed using a grader.
- Dry-mix Cement was spread then mixed with the in-situ soil to create the dry-mix.
- Wet-mix. Renolith was mixed to the required ratio in the water truck. The diluted Renolith was sprayed over the dry-mix material. The wetted material was thoroughly mixed. The specified density of the wetted material was not less than 95% maximum dry density.
- Compact. The pavement was compacted using a roller.
- Finish. An asphalt concrete wearing surface was applied.
Note: Mixing was done with the grader rather than a specialised stabilisation machine. This is generally not considered best practice. However, it was possible in this case because the base layer was thin.
Ekkamai-Ram Inthra Road Bicycle Track – 1997
Review - 2023
Using Google Earth – street view it is possible to inspect the current state of the pavement. The track appears to be in very good condition a quarter of a century later.
The project was very successful in all key aspects:
- Construction cost. Very low. At approx AUD$15 per sqm (inflation adjusted), the construction cost was much lower than alternates such as unbound granular or concrete pavement.
- Construction time. Very fast. In-situ stabilisation is an inherently fast construction method. The 60000sqm project was completed in 20 days – an average of 3000sqm per day. Even faster construction is now possible with the advances in stabilisation machinery.
- Environment / Carbon footprint. Very low. The project used in-situ material, eliminating the carbon cost of quarrying and transport processes. The pavement was very thin in comparison to a typical unbound granular design, thereby much less material was consumed. The base mix used 5% cement, whereas typical concrete consists of 10%-15% cement. The carbon footprint could have been reduced further by using a low-carbon cementitious binder in lieu of portland cement.
- Resilience / Whole-of-life cost. Excellent. No apparent degradation after 25 years.
Conclusion
In-situ silty-sand soil was stabilised with Renolith and cement to form the base layer for the Ekkamai-Ram Inthra Road bicycle track. The construction process was fast, low-cost and low-carbon. The bicycle track remains in good condition after more than 25 years. The project stands as a testament to the successful integration of environmental considerations into urban infrastructure development. It is an inspiration for cities worldwide to prioritise eco-friendly transportation alternatives and create a greener, more resilient urban landscape.