Stabilisation of Malmi soft clay with traditional and low-CO2 binders

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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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Deep soil mixing (DSM), a soil improvement method, is a carbon-intensive activity due to the traditional use of lime and cement as soil binders, which generate large carbon emissions during their production. There is, thus, a growing need for the decarbonisation of infrastructure construction activities, such as DSM, as European cities work towards their carbon-neutrality goals. This paper presents a case study where soft, sensitive postglacial clay from northeast Helsinki is stabilised with the traditional lime-cement (50:50) binder and six alternative low-carbon binders. The low-carbon binders are composed of reduced lime and cement quantities and/or different by-products that include Lime Kiln Dust (LKD), biomass-based fly-ash from bioenergy production, blast furnace slag and the mineral gypsum. The effects of the stabilisation of the alternative binders on the studied clay are evaluated through the results from drained triaxial tests. The lime-cement (50:50) binder is then used as a reference to evaluate the performance of the alternative binders. Additionally, the porosity and porosity distribution of selected stabilised samples were evaluated with the autoradiography technique (AG). Four of the alternative binders showed similar strength levels, at the same confining pressures after 28 days of curing, when compared with the reference binder. Moreover, a higher strength development than the reference binder was observed after 60 days in binders such as the partially LKD-based binder and the gypsum-quicklime-cement mix. Likewise, similar effects of confinement on volumetric behaviour and ductility were exhibited by the binders with comparatively higher strength. Last, results from the AG also showed similarities in terms of porosity and porosity distribution among the stabilised samples with reference and selected low-carbon binders. In general, results show that the inclusion of alternative and side streams material in DSM has the potential to be a more ecological solution with high binding efficiency for soft and sensitive clay improvement.
soil stabilisation, deep soil mixing, carbon dioxide emissions, soft clay
Lopez Ramirez , A & Korkiala-Tanttu , L 2023 , ' Stabilisation of Malmi soft clay with traditional and low-CO2 binders ' , TRANSPORTATION GEOTECHNICS , vol. 38 , 100920 .