Kaolinitic calcined clays: Factors affecting its performance as pozzolans

Five natural kaolinitic clays from different regions of Argentine, with different kaolinite content, different impurities and different degree of crystallinity were calcined in a fixed-bed electrical furnace at 700 °C. Clays were characterized by X-ray diffraction (XRD) and Fourier transformed infra-red spectrometry (FTIR) that provides an index about the order/disorder of the structure. After heat treatment, the structural changes were characterized by XRD and FTIR, and pore size distribution and specific surface were determined. Their pozzolanic activity was evaluated with the Frattini test, electrical conductivity in saturated Ca(OH)₂ solution and compressive strength on mortars at 7, 28 and 90 days. Among tested clays, four of them can be classified as pozzolan by the Frattini test. The pozzolanic activity of the natural clays showed good correlation with the content of kaolinite, the inversed of structure order determined by FTIR, and the specific surface of calcined clays. This study confirms that natural clays other than pure kaolinite can be interesting pozzolanic materials when thermally activated.     

Computing and interpreting Fisher Information as a metric of sustainability: regime changes in the United States air quality

As a key tool in information theory, Fisher Information has been used to explore the observable behavior of a variety of systems. In particular, recent work has demonstrated its ability to assess the dynamic order of real and model systems. However, in order to solidify the use of this metric for measuring sustainability, it is pertinent that Fisher Information be understood both conceptually and practically. As such, this document has been developed as a guide for interpreting Fisher Information as sustainability metric. Moreover, this study provides details on an analytical and numerical approach to estimating Fisher information based on the evaluation of changes in the system’s trajectory for determining stable and unstable regimes in real systems, which might represent sustainable or unsustainable systems. Using this novel approach, the sustainability of US air quality characterized by criteria pollutants (i.e., lead, carbon monoxide, ozone, nitrogen dioxide, and sulfur dioxide) was assessed from 1980 to 2009. Further, the precision of Fisher Information computations was examined, thereby establishing an alternative procedure for evaluating real systems characterized by noisy and sparse datasets. Throughout this article, the reader is led through the analysis of Fisher Information results with the goal of both providing guidance on the interpretation of Fisher Information and giving a more tactile understanding of the results applied to sustainability assessment.