Experimental and Theoretical Evidence of the Overcharging in Calcium-Silicate-Hydrate

2006

International audience

Kinetics of tricalcium silicate hydration : Physico-chemical concepts.

2008

International audience

Intrinsic Elastic Properties of Calcium Silicate Hydrates by Nanoindentation

2007

International audience; To understand the mechanical properties of cement materials is obviously one of the main purposes of the material science. But the mechanical properties measures of a cement piece by conventional methods (vibration, compression, etc.) are largely dependent on the sample porosity. Hence, the result gives information about the sample density rather than on the intrinsic mechanical properties of the material itself. This work aims to present results on cement materials (alite and C-S-H) mechanical properties obtained by nanoindentation using an atomic force microscope (AFM). The material Young modulus in the z-direction is obtained by applying a force perpendicular to t…

Thermodynamic and structure properties of clay dispersions : A Monte Carlo study

2010

International audience

Adsorption of multivalent ions in cementitious materials : Importance of electrostatics

2008

The Cement Cohesion: an Affair of Electrostatics

2007

International audience

Béton, ciment et développement durable.

2006

National audience

Hydrating cement paste : from chemistry and physics to material science.

2009

International audience

Apports de la rhéométrie dynamique et du couplage rhéométrie-microcalorimétrie pour l'étude de la cohésion des pâtes de ciment

2008

National audience; Le passage de la pâte de ciment d'un matériau mou à un solide dur se produit en plusieurs étapes successives. Tout d'abord, les grains anhydres coagulent pour former une structure connectée, puis, les hydrosilicates de calcium (noté C-S-H) qui sont les principaux produits d'hydratation du ciment précipitent sur la surface des grains en particulier aux points de contact préalablement formés et vont ainsi former la phase percolante de la matrice cimentaire. Ces hydrosilicates, particules nanométriques, renforcent la structure en augmentant la surface de contact entre les grains. La cohésion de la pâte de ciment augmente alors avec la quantité d'hydrates formée. Une fois que…

Hydration of silicate phase and mechanical evolution in 'alite-tricalcium aluminate-gypsum' complex system

2007

International audience; Using simultaneously the dynamic mode rheometry and the calorimetry, it has been possible to specify interactions between the components of “alite-C3A-gypsum” system. The concept of "mechanical efficiency of calcium silicate hydrates" (R = dG' /dQ, is the increase in the elastic modulus dG' corresponding to the formation of a certain quantity of CSH, estimated by released heat dQ) was introduced to quantify the effect of the mixtures on the cohesive properties of C-S-H. For the system alite-C3A : the presence of aluminate ions decreases both the growth rate of CSH and R; for the great quantities of C3A, there is a positive effect of the surface developed by AFm on R.…

Influence of high nitrate salts concentration on dimensional variations of mortars under wet curing

2008

Cementation is a widely applied technique for the conditioning of low- and intermediate-level radioactive wastes. In particular, the use of cement is an attractive procedure to immobilize evaporator concentrates from aqueous effluents treatment. This study is devoted to bring information on the influence of concentrates mixing solution on the dimensional variations under wet curing of simulated solidified waste forms with high ionic strength. In this study, the salinity of the evaporator concentrates was simulated by adding sodium or potassium nitrates. The length changes were measured, with displacement gauges consisting in linear variable differential transducers. Mortars prepared with so…

Colloidal Behavior of C-S-H Nanohydrates in Cement Paste

2010

International audience; Among the hydrates constituting a cement paste, C-S-H is the main component, it represents at least 60 % of the fully hydrated paste. C-S-H has a lamellar structure similar to that of a rare mineral, tobermorite. The germination and growth of the C-S-H particles result in increasing mechanical resistance (strength, cohesion). Mechanical experiments show that the intrinsic properties of the paste remain the same throughout the hydration process. Indeed, despite its very high compression strength properties the hydrated cement paste retains the same very low critical strain (~10 -4) characterizing a small elastic limit of the material. More recently, AFM experiments ha…

The liquid solid transition in cementitious materials.

2007

International audience

Modelling hydration and setting of cement.

2006

International audience

Tricalcium silicate modeling and numerical simulations

2010

International audience; In order to identify and quantify what is modified when tricalcium silicate hydration rate varies, we have developed a model to simulate experimental evolution of reaction advancement versus time. It is experimentally observed that the hydrates formation consists of a primary heterogeneous C-S-H nucleation leading to the formation of clusters followed by the anisotropic growth of these clusters. In our model, C-S-H nucleation is described by a random distribution of clusters on a surface. We split the growth step into two processes corresponding to the clusters growth on the surface (parallel growth) and the increase of the cluster thickness (perpendicular growth). E…