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Deneele D.,Institute Francais des science et des Technologies des Transports | Deneele D.,University of Nantes | Le Runigo B.,Institute Francais des science et des Technologies des Transports | Cui Y.-J.,ParisTech National School of Bridges and Roads | And 2 more authors.
Construction and Building Materials | Year: 2016

Durability of lime-treated soil structures, such as earth dams, dikes or river levees, is related to stability, or long term physicochemical evolution of soils in their service environment. The present work aims at (i) providing information on the long term physicochemical behaviour of lime-treated soils subjected to leaching, and (ii) assessing if leaching could be detrimental to the durability of lime-treated soils. Lime addition improves the unconfined compressive strength (UCS) of silt by formation of secondary cementitious phases (C-A-S-H, C-A-H,...) and carbonation of lime. The UCS increases with the lime added. Leaching induces a leaching of these secondary phases, as recorded by the evolution of the chemistry of the leachates. The results obtained indicate that addition of lime up to soil lime modification optimum (LMO at 1% lime) is not sufficient to maintain long term durability of lime-treated soils. Addition of important lime contents extends the resistance of materials, but the UCS decreases. However, leaching of cementitious phases has no effect on the hydraulic conductivity of materials. © 2016 Elsevier Ltd. All rights reserved.

De Windt L.,MINES ParisTech | Deneele D.,Institute Francais des science et des Technologies des Transports | Deneele D.,University of Nantes | Maubec N.,Institute Francais des science et des Technologies des Transports
Cement and Concrete Research | Year: 2014

Abstract The effects of duration (1-100 days) and temperature (20 and 50 C) were assessed from batch tests for Ca-bentonite mixed with 10 wt.% lime. The pozzolanic processes were monitored over time by 29Si NMR (Cement Concr. Res. 42, 2012), TGA-DTA, XRD and chemical analysis. Modeling considered kinetics and thermodynamics of mineralogical transformations and cation exchange. Kinetic laws were dependent on pH and temperature (Arrhenius energy). Lime hydration occurs within hours, modifying the bentonite exchangeable population and increasing the pH. These alkaline conditions initiate the pozzolanic reactions in a second stage. The rate-limiting step is the dissolution kinetics of the bentonite minerals, i.e. a relatively fast and total consumption of cristobalite in parallel to a long-term slower dissolution of montmorillonite. First C-S-H and then C-A-S-H are formed consequently. Temperature speeds up the pozzolanic reaction kinetics by a factor 5 from 20 to 50 C, corresponding to an apparent activation energy of 40-50 kJ/mol. © 2014 Elsevier Ltd.

Deneele D.,Institute Francais des science et des Technologies des Transports | Deneele D.,University of Nantes
1st IMEKO TC4 International Workshop on Metrology for Geotechnics, MetroGeotechnics 2016 | Year: 2016

Composed of discrete particles and particle groups, a soil mass or a reconstituted soil mass should be considered as a continuum for analysis and design. Even with the development of numerous techniques of investigations, the link between the macroscopic behavior and the particle arrangement in soils is still under debate owing the complexity of the system, the different levels of investigations. However the shape of the particles, the particle arrangements, the strength of the particles or the water content of a soil govern the soil microstructure or fabric and the macroscopic properties as the permeability, the compressibility and strength. Some examples presented in this paper illustrate how the use of conventional scanning electron microscope (SEM) can be useful in the description of soil fabric and bring information in the understanding of the soil properties. © 2016, IMEKO-International Measurement Federation Secretariat. All rights reserved.

Vitale E.,University of Cassino and Southern Lazio | Deneele D.,Institute Francais des science et des Technologies des Transports | Deneele D.,University of Nantes | Russo G.,University of Cassino and Southern Lazio | Ouvrard G.,University of Nantes
Applied Clay Science | Year: 2016

In the paper an experimental multi-scale investigation on the influence of pore water chemistry on the short-term behaviour of lime treated soil is presented. Sedimentation tests on kaolin suspensions under different chemical environment have been performed and interpreted, taking into account the effects of clay particles interactions on the soil skeleton formation. The experimental evidences at volume scale of the samples have been directly related to the results of micro-scale investigations. Modification of surface charge and its influence on soil fabric has been investigated by means of zeta-potential measurements, Dynamic Light Scattering (DLS) and Scanning Electron Microscopy (SEM). The effects of lime content, cation valence and source of calcium ions on the surface charge of kaolin particles have been considered. The addition of lime increased the average size of particles aggregates in the short term. The fabric evolution affected the formation of the soil skeleton during sedimentation, influencing its void ratio and compressibility, highlighting the link between microstructural features and mechanical behaviour of lime treated samples. © 2016 Elsevier B.V.

Pomakhina E.,University of Nantes | Deneele D.,University of Nantes | Deneele D.,Institute Francais des science et des Technologies des Transports | Gaillot A.-C.,University of Nantes | And 2 more authors.
Cement and Concrete Research | Year: 2012

Lime is widely used as additive to improve the mechanical properties of natural soil used in earthworks. However, the physico-chemical mechanisms involved are yet not well understood. In order to develop and optimize this treatment method, a better understanding of the interaction between lime and the minerals of the soils, in particular clay minerals, is required. In this study, Ca-bentonite was treated with 2, 5 and 10 wt.% of lime during 1 to 98 days. Modifications in the Si local environment were then monitored by solid state nuclear magnetic resonance to investigate the pozzolanic reaction. All the soil mineral phases contribute to the release of Si and to the pozzolanic reaction, with a rapid and total consumption of Si-polymorph and an exacerbated dissolution of montmorillonite. Mechanism of C-S-H formation, function of the Ca content in the system, was found to match the sorosilicate-tobermorite model described in cement systems. © 2012 Elsevier Ltd.

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