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Nguyen T.T.H.,ParisTech National School of Bridges and Roads | Cui Y.J.,ParisTech National School of Bridges and Roads | Tang A.M.,ParisTech National School of Bridges and Roads | Herrier G.,LHOIST Recherche et Developpement | And 3 more authors.
Unsaturated Soils: Research and Applications - Proceedings of the 6th International Conference on Unsaturated Soils, UNSAT 2014 | Year: 2014

Unsaturated hydraulic conductivity is key factor governing soil swellings under the effect of frost because it conditions the water transfer driven by the cryo-suction generated by soil freezing. In this study, the unsaturated hydraulic conductivity of a compacted untreated and lime treated silty soil was determined using two methods: 1) calculations based on a capillary tube model involving the pore size distribution curve obtained by the technique of mercury intrusion porosimetry technique, and 2) determination by the instantaneous profile method using the results from isothermal infiltration/drying tests. This enables the two methods to be compared and discussed. Significant difference was observed, showing the limitation of the capillary tube model used in predicting the hydraulic conductivity of soils. However, the calculated hydraulic conductivity-suction curve presents a similar shape to the measured one, suggesting that the main mechanism considered in the model is appropriate. © 2014 Taylor & Francis Group. Source


Fourmentin M.,University Paris Est Creteil | Ovarlez G.,University Paris Est Creteil | Ovarlez G.,Solvay Group | Faure P.,University Paris Est Creteil | And 4 more authors.
Rheologica Acta | Year: 2015

The rheological properties of a suspension of lime in water (lime putty) are studied with the help of creep tests in a wide range of deformations including very small values. The results are compared with those obtained with a cement paste and several similarities between the two systems are observed. It is shown that the apparent yield stress of a lime suspension is the sum of two components: one due to standard reversible colloidal interactions and one due to the formation of a brittle structure associated with the formation of links due to dissolution–precipitation mechanisms. This second component increases with the time of rest as the square root of time, and the corresponding structure irreversibly breaks as soon as some significant deformation has been imposed. We show that similar structures are formed at concentrations between 25 and 34 % (solid volume fraction) and evolve in a similar way when the time is scaled by a factor decreasing with the solid fraction. © 2015, Springer-Verlag Berlin Heidelberg. Source


Nguyen T.T.H.,ParisTech National School of Bridges and Roads | Cui Y.J.,ParisTech National School of Bridges and Roads | Herrier G.,LHOIST Recherche et Developpement | Tang A.M.,ParisTech National School of Bridges and Roads
Geotechnical Engineering for Infrastructure and Development - Proceedings of the XVI European Conference on Soil Mechanics and Geotechnical Engineering, ECSMGE 2015 | Year: 2015

The hydraulic conductivity is a key parameter in evaluating the water transfer in soils. For the subgrade soils treated with lime, it is also an important factor to be accounted for when assessing the soils resistance to frost. To the authors' knowledge, the effect of lime treatment on the hydraulic conductivity of unsaturated soil is still subject to debate. In this study, the hydraulic conductivity of a limetreated silty soil was determined experimentally using an infiltration column equipped with tensiometers at different heights. Three quicklime dosages were considered: 0% (untreated soil), 2% that corresponds to the lime fixation point (LFP), and 4%. The effect of curing times was examined: as-treated, 28 days and 90 days. The saturated hydraulic conductivity was also determined by variable head permeability test. In order to complete the results for applying the simultaneous profile method when determining the unsaturated conductivity, the water retention curves were determined for each configuration. It appears that after a 28 days curing time, the hydraulic conductivity increases, especially in the case of high lime dosage. This increase can be attributed to the effect of flocculation. On the contrary, after a longer curing time of 90 days, the significant pozzolanic reactions led to a decrease of hydraulic conductivity. © The authors and ICE Publishing: All rights reserved, 2015. Source


Lesueur D.,LHOIST Recherche et Developpement | Peter U.,LHOIST Recherche et Developpement | Verhelst F.,Lhoist Group Marketing
Cement, Wapno, Beton | Year: 2011

Quicklime is a key component of Autoclaved Aerated Concrete (AAC), with typical quicklime contents of order 15 wt.% in Europe. It is the mostly used source of calcium oxide that eventually ends up as tobermorite in the final product. In this paper, we describe the research performed at Lhoist in order to assess the influence of quicklime on AAC. Several types of quicklimes were used, differing by their origin and reactivity. They were incorporated together with other fixed ingredients (cement, quartz,.) in several AAC recipes with final densities ranging from 350 to 550 kg/m3, corresponding to the European P2 - 0.35, P2 - 0.4 and P4 - 0.55 classes (EN 771-4). The study consisted first in following the green cake expansion of the different recipes. Then, the green cakes were autoclaved for 10 hours at 11 bars of steam pressure. The obtained AAC blocks were then tested for compressive strength and density. The study showed that quicklime reactivity had low effect on green cake penetration value. However, quicklime reactivity had a major effect on green cake expansion. Too reactive a quicklime generated a poor pore structure as detected by a fallback effect and a below-specification compressive strength of the low density AAC. Then, quicklime slaking curve was not sufficient to anticipate the green cake expansion for a given recipe. Quicklimes with similar reactivity but different origin could had very different behaviour in the AAC. Finally, the behaviour of the too-reactive quicklimes would probably have been easily corrected by decreasing the water temperature. Source


Fourmentin M.,University Paris Est Creteil | Faure P.,University Paris Est Creteil | Gauffinet S.,University of Burgundy | Peter U.,LHOIST Recherche et Developpement | And 4 more authors.
Cement and Concrete Research | Year: 2015

Abstract The acceleration of a cement paste setting as a result of lime addition may be shown from isothermal calorimetry measurements. We investigated the underlying mechanisms through two techniques that provide information on porous structure (using Nuclear Magnetic Resonance) and mechanical properties (elastic modulus measured by rheometry). The correlation of the two sets of results on a cement paste clearly reveals the successive steps of setting, and particularly highlights the so-called induction period. We show that this induction period disappears in the presence of lime, leading to an acceleration of the setting. We also show that beyond some critical concentration of added lime the acceleration of setting is negligible. © 2015 Elsevier Ltd. Source

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