Michel Chabannet

Microstructure and Porosity of Metakaolin Blended Cements

Five compositions with 10% to 50% metakaolin for cement substitution were studied. The rate of hydration was studied from the compressive strength after up to 6 months of curing and from the hydrates formed (DTA-XRD). The metakaolin addition considerably reduced portlandite content in the hydrated cement and contributed to the formation of hydrated gehlenite which is not present in OPC paste. The microstructure study (SEM) shows that pozzolanic cement pastes were less crystallized than plain pastes. Mercury intrusion was used to measure porosity of hydrated cement pastes. The porosity with blended cements was higher than that with OPC, except for 10 and 20% metakaolin substitution. Evolution of the pore size distribution was studied: the pozzolanic pastes enhance small diameters.

Design of a novel system allowing the selection of an adequate binder for Solidification/Stabilization of wastes

Abstract Literature review shows that there is a lack of complete and consistent data on waste-binder interactions. Few links exist between research on the Solidification/Stabilization (S/S) mechanisms and the formulation of binders for immobilization. Therefore, a twofold program was developed allowing both to be done in parallel. This protocol had two targets: understanding the mechanisms involved in the S/S of heavy metals for each type of binder and rating the binder capacity for fixing heavy metals. The experimental procedure relies on two substrates: 1) the study of suspensions by means of conductimetry, XRD, FTIR, DTA, SEM-EDXA, ICP, ion chromatography, and colorimetry; and 2) the study of pure pastes for leaching tests and microstructural characterization (XRD, FTIR, DTA, SEM-EDXA). Results confirm whether the pollutant modifies the hydration or not, give access to the extent of “binder stabilization” without taking into account the solidification part, and elucidate the mechanisms involved.

Study of the reactivity of clinkers by means of the conductometric test

Abstract The conductometric test has been developed by Vernet in order to study cement-admixture systems. An investigation has been carried out to see how this test can be used to control the reactivity of clinkers. Six cements provided by the same plant were studied. The conductometric test showed different behaviours, in terms of initial and maximal conductivity values and duration of the dormant period. These results, completed by the analyses of the pore solutions, explained the different 2-day and 7-day compressive strengths. The conductometric test could be an interesting way to follow the reactivity of ement.

HYDRAULIC ACTIVITY OF SLAGS OBTAINED BY VITRIFICATION OF WASTES

Rather than landfilling municipal waste incineration bottom ash, it is possible to produce latent hydraulic materials for blended cements by a smelting process. The waste material is mixed with various amounts of quicklime, calcium carbonate, alumina, calcium chloride, and iron oxide; then, it is smelted at about 1500 deg C (2732 deg F) and cooled to obtain a synthetic glassy slag. After being ground, the slag is activated by clinker and gypsum. In the present study, the results concerning two blended cements containing 47.5 and 76 percent synthetic slag, respectively, are presented. The mechanical properties of these cements are compared to those of a blast furnace slag blended cement. The influence of the gypsum content on the strength of mortars is also studied. It is shown that the synthetic slags present sufficient hydraulic activity and low heavy metal content. In some cases, the performances are the same as those obtained with a ground granulated blast furnace slag.