In Sri Lanka, the shoulder in asphalt pavements has been constructed using the materials transported from borrow pit in the iRoad Project due to the low quality of in-situ soils. After excavating 150~200mm thick and 500mm wide shoulder area, the borrow pit materials are placed and compacted according to specifications. The excavated in-situ soils are dumped in designated location. It is estimated that this process of shoulder construction is not economical due to high material transportation cost and can also induce the environmental issues by disposal of in-situ soils. It can also cause distresses such as surface rutting and edge drop-off in soft shoulder section due to bearing capacity failure and off-tracking of vehicle. The heavy rainfall in Sri Lanka can induce severe erosion problem when using the soft shoulder. To improve the strength and durability of pavement shoulders in the iRoad Project, the soil stabilization will be a good alternative to solve the above mentioned problems. The use of in-situ soils with addition of soil stabilizer enables to reduce the construction cost of shoulder section and mitigate the environment issues. The objective of this task is to review the application of soil stabilization method for soft shoulder construction in the iRoad Project. Firstly, the quantitative analysis of soil strength improvement due to soil stabilization was done for soil samples collected from iRoad construction sites. Two types of soils were selected from iRoad Project sites and prepared for soil stabilization testing by the Road Development Authority. Secondly, the appropriate stabilizer was selected at given soil type based on test results. Three different stabilizers, ST-1, ST-2, and ST-3, produced in Korea were used for estimating soil strength improvements. Finally, the optimum stabilizer content was determined for improving shoulder performance. The uniaxial compressive strength (UCS) test was conducted to evaluate the strength of stabilized soil samples in accordance with ASTM D 1633. The use of bottom ash as a stabilizer produced from power plant in Sri Lanka was also reviewed in this task.

• Hee Mun Park(Korea Institute of Civil Engineering and Building Technology)
• Su Hyung Lee(Korea Institute of Civil Engineering and Building Technology)
• Pyeong Jun Yoo(Korea Institute of Civil Engineering and Building Technology)
• Byung Sik Ohm(Korea Institute of Civil Engineering and Building Technology)
• Ki Soo Park(Korea Institute of Civil Engineering and Building Technology)