Browsing by Author "Vargas, Felipe"

Now showing 1 - 7 of 7
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    A Study on Copper Mine Tailings to Be Used as Precursor of Alkali-Activated Materials for Construction Applications
    (2025) Morales Castro, Luis Felipe; Loyola Fernández, Estefanía Francisca; Castro Quijada, Matías Daniel; Vargas, Felipe; Navarrete Leschot, Iván Ignacio; Eugenin Soto, Claudia Andrea; Marquardt Román, Carlos Jorge; Videla Leiva, Álvaro Rodrigo
    This research presents a novel methodology to classify copper tailings according to their potential as alkali-activated materials (AAMs) for construction applications. The methodology includes geochemical and mineralogical characterization via QEMSCAN and X-ray fluorescence, with mechanical performance evaluation through compressive strength test (UCS). A three-phase diagram based on Al2O3, Fe2O3, and CaO-MgO-K2O is proposed for a fast screening of copper tailing potential to be used as a construction material. In this paper, three copper tailings were chosen to test the methodology, and a set of five samples for each tailing have been geopolymerized for testing. Copper tailing samples were mixed with 0, 2.5, 5, 7.5 and 10% by mass of Ordinary Portland Cement (OPC) to evaluate the effect on performance when a chemical co-activator is used to improve material reactivity. Compressive strength testing was applied on 2 cm3 cubes after 28 days of curing at 60 °C, yielding values from 6 to 26.1 MPa. The best performing sample featured a Si/Al ≅ 3 ratio and a mineralogy with significant presence of reactive species such as plagioclase and K-feldspar (≅42%). In contrast, high levels of Fe2O3 (≥12%), clay (≥7%), and pyrite (≥4%) were associated with reduced mechanical performance.
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    Copper entrapment and immobilization during cement hydration in concrete mixtures containing copper tailings
    (2021) Vargas, Felipe; Alsina, Marco A.; Gaillard, Jean-François; Pasten Gonzalez, Pablo Arturo; López, Mauricio; CEDEUS (Chile)
    The use of copper tailings as supplementary cementitious material can reduce the environmental impacts ofconcrete production and the mining industry. A key concern limiting its application is the potential leaching oftoxic metals from the cementitious matrix, especially copper. To analyze and reduce the risk of leaching, themechanisms by which copper is entrapped in the cementitious matrix were investigated, by combining micro-scopic and spectroscopic approaches. Decreasing the water-to-binder ratio was statistically relevant to reducecopper leaching. Scanning Electron Microscope micrographs allowed to spatially localize enriched copperclusters within the cementitious hydration products. In the early stages of the cementitious hydration (i.e., 24 h),no spatial correlation between copper and hydration products was found; however, after seven days, copper wasspatially associated with calcium silicate hydrates. Cu K-edge X-ray absorption near edge structure spectroscopyprovided insights into the chemical speciation of copper in the cementitious matrix. It showed that copper sulfideand oxide phases persisted, whereas the copper sulfate phases were prone to dissolution and reprecipitation ascupric hydroxides induced by the relatively high pH from calcium hydroxides formed during hydration. Pro-moting the formation of hydration products can further reduce copper leaching from the alkaline cementitiousmatrix. A better understanding of metal entrapment mechanisms could lead to new strategies that reduce themobility of toxic elements when using copper tailings, increasing their use as a replacement of cement. With thisknowledge, it is expected to answer if it is possible to improve the copper entrapment into the cementitiousmatrix and if there is a risk of leaching once is entrapped.
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    Impact of mixture design and production parameters on the crushing strength of cold-bonded alkali activated aggregates made from iron tailings
    (2026) Loyola Fernández, Estefanía Francisca; Eugenin Soto, Claudia; Vargas, Felipe; Videla Leiva, Álvaro Rodrigo; Navarrete Leschot, Iván Ignacio
    This study explores the production and performance of cold-bonded alkali-activated artificial aggregates (CB- AAA) made from highly crystalline iron tailings, a low-reactivity mining by-product. A factorial experimental design was used to assess the influence of five key parameters on crushing strength: aggregate particle size, alkaline activator molarity, co-activator dosage, curing temperature, and curing time. The resulting aggregates exhibited bulk densities from 824 to 1002 kg/m³ , water absorption between 14.78 % and 25.68 %, and crushing strengths ranging from 0.18 to 3.24 MPa. A second-order polynomial regression model was developed and validated, identifying curing temperature as the most significant factor. To evaluate structural applicability, concrete specimens were prepared with 30 % and 100 % replacement of natural coarse aggregates. Higher- quality CB-AAA mitigated compressive strength losses, with partial replacement mixtures retaining up to 60 % of the reference strength. These results demonstrate the feasibility of using iron tailings in low-carbon construction materials despite the low reactivity of these waste materials, and they offer new insights into the role of mixture design and processing conditions in optimizing the performance of CB-AAA for concrete applications.
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    Improvement of the thermal performance of hollow clay bricks for structural masonry walls
    (2024) Vera Araya, Sergio Eduardo; Figueroa Cofré, Camilo Iván; Chubretovic Arnaiz, Soledad; Remesar Lera, José Carlos; Vargas, Felipe
    Although structural masonry walls are widely used in construction, achieving lower U-value is crucial to minimize energy losses and greenhouse gas emissions. The effect on the U-value of hollow clay masonry walls is evaluated by modifying the clay and mortar thermal conductivities, as well as the brick grid and thickness. Heat transfer through bricks and walls was modeled using a 3D-finite element method while model validation was based on experimental tests. Smaller rectangular cavities reduce the U-value to 0.761 W/m2K; increasing the brick thickness reduces the U-value to 0.563 W/m2K. Moreover, reducing the clay thermal conductivity showed negligible reductions in the wall U-value.
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    Nuevos áridos para la construcción: hacia una economía circular para una industria más sustentable y una infraestructura más resiliente
    (Centro de Políticas Públicas UC, 2024) Navarrete Leschot, Iván Ignacio; Vargas, Felipe
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    Replacement of pozzolanic blended cement by supplementary cementitious materials: Mechanical and environmental approach
    (2023) Navarrete, Ivan; Valdes, Juan; Lopez, Mauricio; Vargas, Felipe
    Pozzolanic blended cements, used in several markets, can be mixed with supplementary cementitious materials (SCMs) to improve environmental performance keeping a similar compressive strength. Many SCMs are industrial byproducts that do not require intensive processing. Six industrial byproducts were studied as replacement of pozzolanic blended cement. Reactivity, compressive strength, and environmental performance were measured. Results showed that the use of SCMs as partial replacement for pozzolanic blended cement increases the reactivity of cement and, therefore, the compressive strength of cementitious pastes. Furthermore, environmental results showed beneficial or detrimental effects depending on replacement level, compressive strength, and CO2 footprint of each SCM.