Speaker
Description
The incorporation of organic liquids in cement-based materials is of interest for various applications like the formation of porous material through emulsion templating and removal of the dispersed phase, the design of composite materials with improved and/or combined properties or the immobilization of industrial wastes. Immobilization of wastes into cementing materials by stabilization and solidification (S/S) is a common procedure, because it ensures chemical stabilization of many compounds and produces a mechanically stable waste form. Several ways of incorporating organic liquids into cementing materials are distinguished. It is either a direct incorporation into the reactive cementing slurry, a pre-emulsification prior to the addition of solid precursor or a solid impregnation prior to the addition into the cementing slurry. The pre-emulsification process is particularly interesting because it offers the possibility of incorporating a large amount of organic liquid, while ensuring that no phase separation will occur until hardening of the continuous cementing phase. Portland cement has been widely studied for the immobilization of many organic compounds with issues encountered in regards to strength development. Comparatively, alkali-activated materials (AAM), and particularly geopolymers, display superior performances against organic contamination compared to Portland cement. Indeed, while the presence of organic compounds generally disturbs the hardening of hydraulic binders, the mechanism of geopolymer formation is such that liquid/liquid emulsion might be easier for the synthesis of composite organic/inorganic materials.
In this research, a significant amount of low viscosity pure mineral oil (20%vol) is successfully immobilized in alkali-activated materials (AAM), either based on metakaolin or blast furnace slag. Surfactants are required to achieve oil emulsion stability. Visual observation, torque measurement and rheology evidence two distinct groups of surfactants. One group contributes to structuring the oil/AAM fresh mix, with greater torque and viscosity than without surfactant; the other is made of non-structuring surfactants, with no change in torque or viscosity. Each group depends on the AAM considered. Whatever the surfactant, both the interfacial tension between oil/activating solution and the oil droplet size decrease significantly. However, although contributing to stabilize the emulsion, interfacial tension alone does not explain the structuring behavior. Characterization of diluted ternary suspensions (solid particles-oil- activating solution) relates the structuring effect to interactions between oil and solid particles, through the surfactant molecule polar heads and tails. An original mechanism explaining structuration is discussed.
| Speaker's title | Mr |
|---|---|
| Affiliation | Commissariat à l’énergie atomique et aux énergies alternatives |
| Do you wish to participate as a Young Professional? | No |
| Do you wish to be considered for a Young Professional grant? | No |
