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As society moves towards decarbonisation, it is important to assess the hydromechanical behaviour of binders that could offer a low-carbon alternative to Portland cement in ground improvement technologies. This work considers two such alternatives: one still largely unexplored (metakaolin-based geopolymers) and a better known one (colloidal silica). Results from unconfined compressive strength, permeability tests, undrained monotonic and cyclic triaxial tests on granular soils (sand and silty sand) treated with those two binders are presented and discussed, emphasizing similarities and differences with the response of similar soils treated with other conventional and unconventional binders. Effects of silt content, curing conditions and soil/binder ratios are examined. Both colloidal silica and metakaolin-based geopolymer significantly improve the mechanical properties of the treated soils, although the geopolymer results in a stronger and stiffer material. Both treatments reduce much the permeability of the treated soil, but the reduction achieved with colloidal silica is larger. Key words: sand-silt mixture, triaxial tests, permeability, metakaolin-based geopolymer, colloidal silica. Dans un contexte de decarbonisation de la societe, il est important d'evaluer le comportement hydromecanique des liants qui pourraient offrir une alternative a faible teneur en carbone au ciment Portland dans les technologies d'amelioration des sols. Ce travail considere deux de ces alternatives : une encore largement inexploree (geopolymeres a base de metakaolin) et une plus connue (silice colloidale). On presente et discute les resultats d'essais de resistance a la compression non confinee, d'essais de permeabilite, d'essais triaxiaux monotones et cycliques non draines sur des sols granulaires (sable et sable silteux) traites avec ces deux liants, en soulignant les similitudes et les differences avec la reponse de sols similaires traites avec d'autres liants conventionnels et non conventionnels. On examine les effets de la teneur en limon, des conditions de durcissement et des rapports sol/liant. La silice colloidale et le geopolymere a base de metakaolin ameliorent tous deux de maniere significative les proprietes mecaniques des sols traites, bien que le geopolymere donne un materiau plus fort et plus rigide. Tous deux diminuent considerablement la permeabilite du sol traite, mais la reduction obtenue avec le silice colloidale est plus importante. [Traduit par la Redaction] Mots-cles : melange de sable et de limon, essais triaxiaux, permeabilite, geopolymere a base de metakaolin, silice colloidale., Introduction Ground improvement techniques enhance the mechanical and hydraulic properties of soils for engineering applications. Several ground improvement methods involve the addition of binders to soils. These methods are usually [...]

Human-induced soil change is attracting increasing attention, yet how to quantitatively measure anthropogenic impact on changes in soil properties remains unclear. Eight selected soil properties--bulk density (BD), sand, silt, and clay content, pH, soil organic matter (SOM), total carbon (TC), and total nitrogen (TN)--at four soil depths (0-10, 10-20, 20-30, and 30-40 cm) were measured across three soil series (Gallion, Latanier and Sharkey) in south-central Louisiana, USA, to quantify changes in soil properties as a function of three contrasting land use types, i.e. forest, cropland, and Wetlands Reserve Program. Partial eta-squared values ([η.sup.2]) derived from two-way analysis of variance were used to quantitatively compare natural factors (soil series) and anthropogenic impact (land use) on these soil properties. Results showed that properties such as BD, pH, SOM, TC, and TN could be easily changed by anthropogenic disturbance, especially at 0-10 cm, while soil texture was mainly a natural factor. The anthropogenic factor accounted for 55.2%, 39.5%, 33.2%, and 36.0% of changes in the soil properties at 0-10, 10-20, 20-30, and 30-40 cm depth, respectively. These findings highlight the anthropogenic impact on selected soil properties. Additional keywords: anthropogenic impact, partial eta-squared ([η.sub.2]), principal component analysis, Wetlands Reserve Program (WRP)., Introduction Jenny (1941) published the famous soil-forming factor equation: s = f (cl, o, r, p, t, ...) where s, cl, o, r, p, and t refer to soil, climate, [...]