Metakaolin Addition to Improve Geopolymerization Process and Properties of Waste Clay-Based Materials

The exploitation of different kind of clayey waste (halloysitic, smectitic/illitic, kaolinitic) for the production of geopolymers in the view of a circular economy of mines is the main goal of this study. In particular, the addition of low percentages of metakaolin (5-15%) was evaluated to improve the chemical-physical properties and the consolidation degree of geopolymeric formulations produced with clays classified as mine’s by-products. In fact, these secondary raw materials are often not sufficient alone to obtain chemically stable formulations with acceptable mechanical properties but require the addition of reactive fillers. All samples contained thermally treated clays (600°C-700°C) and metakaolin as aluminosilicate precursors, alkaline solution of NaOH and Na2SiO3, and were cured at room temperature. The influence on the final products with MK addition was monitored with the evaluation of the chemical stability in water (pH and ionic conductivity measures), the comparison of setting times (Vicat needle) and mechanical performance.

From the second law of thermodynamics to AC-conductivity measures of interacting fermions in disordered media

We study the dynamics of interacting lattice fermions with random hopping amplitudes and random static potentials, in presence of time-dependent electromagnetic fields. The interparticle interaction is short-range and translation invariant. Electromagnetic fields are compactly supported in time and space. In the limit of infinite space supports (macroscopic limit) of electromagnetic fields, we derive Ohm and Joule's laws in the AC-regime. An important outcome is the extension to interacting fermions of the notion of macroscopic AC-conductivity measures, known so far only for free fermions with disorder. Such excitation measures result from the second law of thermodynamics and turn out to be Lévy measures. As compared to the Drude (Lorentz–Sommerfeld) model, widely used in Physics, the quantum many-body problem studied here predicts a much smaller AC-conductivity at large frequencies. This indicates (in accordance with experimental results) that the relaxation time of the Drude model, seen as an effective parameter for the conductivity, should be highly frequency-dependent. We conclude by proposing an alternative effective description — using Lévy processes in Fourier space — of the phenomenon of electrical conductivity.

Electrochemical evidences of the protection efficiency of propargyl alcohol o low-carbo steel in ethanolic solutions by electrical conductivity measures

It is shown that electrical conductivity measurement is a good method to characterize corrosion processes that occur on low-carbon steel in ethanolic solutions. Different aggressive coonditions were tested by changing the water content in distilled ethanol and by adding acid. Propargyl a alcohol inhibits the corrosion reaction. The specific conductivity of the solution decreases in the presence of propargyl alcohol for varying levels of aggressiveness. In dilute acetic acid ethanolic solutions, the proyection efficiency was better in 1.0mM propargyl alcohol than in the other concentrations.

An electrophysiological correlate of Eating Attitudes Test scores in female college students

SynopsisEating Attitudes Test (EAT) scores of forty female college students were compared to their electrodermal activity (EDA) responses when offered a plate of chocolate chip cookies. A significant positive correlation was detected between the EAT scores and the skin conductivity measures associated with the presentation of food. Women with the highest EAT scores also exhibited the greatest sympathetic nervous system responses to a plate of cookies. This finding supports the conclusion that the EAT is capable of identifying individuals who are preoccupied with food or anxious about eating.