Compaction characteristics and hydraulic conductivity of a silty soil treated with sustainable binders

In the framework of a research project financed by Next Generation EU Programme with the Italian Ministry of University and Research (currently ongoing at Università Politecnica delle Marche) related to the possibility of using sustainable binders in soil stabilization, the present note explores the possibility to treat a sandy soil with fly ash activated in an alkaline environment. With this approach two types of waste can be reused: the excavated soil, that otherwise should be disposed, and the byproduct (fly ash) used as binder in the stabilization process. Physico–chemical and mineralogical characterization of the soil and the binder were carried out by X-Ray diffraction, SEM observations and Energy Dispersive X-Ray Spectroscopy. The soil was mixed with 2% fly ash activated with 2% calcium hydroxide from quicklime and the mixture was compacted at different moisture contents. Hydraulic conductivity tests were carried out on samples compacted dry and wet of optimum investigating also the long-term hydraulic behaviour. The experimental results are compared with those of the untreated soil compacted with the same energy, to evaluate the effect of the binder addition. Results show very small variation of the compaction characteristic and a reduction of the hydraulic conductivity of the soil-binder mixtures when compacted wet of optimum. Hydraulic conductivity values of the mixtures always reduces with curing time due to gel form pozzolanic products