With more concrete pavements being constructed over soft soil foundations, the use of coal combustion products, such as furnace (bottom) ash, to provide bridging of soft areas and reduced construction risk by being able to be placed insitu in wet weather, becomes more critical. The use of such materials in improving the bearing capacity and stability of road pavement foundation layers has been documented in the technical literature worldwide. Applications of bottom ash to supplement structural fill in pavement construction have been successfully carried out in Australia and overseas.
The previous section of the Ballina bypass in northern New South Wales extensively used Bayswater bottom ash to assist in reducing settlement and movement of road embankment elements in soft soil areas. With further work proposed to be done in the Clarence Valley where soft soils are prevalent in conjunction with high average rainfall, the use of bottom ash could aid in providing improved materials with respect to bearing capacity and stability. The technical and engineering advantages of using the designed bottom ash blended materials in areas where the ground is expected to settle and consolidate overtime are described.
Furnace Bottom Ash, with compacted bulk density of approx. 0.8T/m3 and Particle Density of approx. 1.7T/m3, provides a lightweight material that occupies more volume per tonne than other natural alternatives and with such an advantage longer haul distances become economically viable.
