Browsing by Author "Vergara, Paulina"

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    Influence of conventional and functionalized carbon nanotubes in hybrid alkaline pastes with fly ash that contain high amounts of SO4
    (2021) Vasquez, Jeison; Gonzalez, Marcelo; Vergara, Paulina; Munoz, Jose F.; Arellano, Juan; Escalona Burgos, Nestor
    This research investigates the effect of incorporating conventional and functionalized carbon nanotubes into a cementitious matrix made of 30% cement and 70% fly ash with high amounts of sulfate. Carbon nanotubes were added in different proportions, and the mechanical and physical properties were evaluated through a compressive strength and minibar test, respectively. The results showed that carbon nanotubes improve the compressive strength up to 17% and the expansion is reduced by 10 times. This research is novel because application of carbon nanotubes in hybrid alkaline pastes with fly ash that contain high amounts of sulfate has not been investigated before. (c) 2021 Elsevier Ltd. All rights reserved.
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    Regolith-hosted rare earth genesis under humid climates in the Coastal Cordillera of the Central Andes
    (2023) Bustos, Nicolas; Marquardt R., Carlos; Roquer, Tomas; Vergara, Paulina
    Regolith-hosted rare earth element deposits (RH-REE) have been recently found in Chile, nonetheless their ore formation controls, which include temperate to arid climate, intrusive rocks with weatherable REE minerals, and gentle slopes or pediplains, among others, differ from the most common deposits in Asia. This work addresses mineralization and exploration methods for RH-REE deposits across the Chilean Coastal Range. The studied prospect is associated with late Carboniferous I-type tonalitic intrusions. Mineralogical analysis (TIMA-X) indicates that allanite and monazite are the main REE-bearing minerals in the host rock. The regolith in the study area is up to 60 m deep and contains an exchangeable-REE concentration up to 2000 ppm, as determined by portable X-ray fluorescence (pXRF) and ICP-MS. We were able to recognize that REE-adsorption takes place both in preserved and partially eroded regoliths. Progressive weathering of these regoliths causes the pedolith/saprolith limit to be dynamic and accumulate REE due to the breakdown of allanite and monazite. Our data shows that the search for pediplains on suitable lithologies, mapping of regolith profiles, and their analysis via pXRF by quantifying yttrium, appears to be a suitable strategy for early exploration of RH-REE deposits in the Chilean Coastal Range.