Performance of Synthetic Lightweight Aggregates for Road Embankment Construction on Improved Soft Soil

The paper presents a study on the performance of innovative synthetic lightweight aggregates (SLAs) made from recycled plastic and biomass fly ash when used in road embankment construction on soft soil. It was ascertained that the SLAs behave just like a granular soil with compressibility and shear strength properties comparable to those exhibited by other natural lightweight aggregates. Two different applications were considered. The first deals with the use of the SLAs as back-fill material of compacted aggregate columns to improve soft soil under the embankment. In this case, the behavior of the embankment in terms of stability, settlements and consolidation time was evaluated using the basic concepts of stone columns method. In the second application, SLAs are used as fill material of the embankment constructed in a single stage on a soft soil improved by vertical drains. The performance of this latter solution was compared to that obtained with the adoption of traditional granular materials by a stage construction method. The results obtained allow the conclusion that SLAs can be used as an effective alternative to traditional natural aggregates NAs in either case. The advantages of using the SLAs instead of NAs as fill material of the embankment were analyzed not only in terms of geotechnical features but also in terms of improvement in road constructive aspects such as time, costs and environmental burdens.