Browsing by Author "Rojas, Eduardo"

Now showing 1 - 9 of 9
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    Assessment of a conservative mixing model for the evaluation of constituent behavior below river confluences, Elqui River Basin, Chile
    (2021) Rossi, Catalina; Oyarzún, Jorge; Pasten Gonzalez, Pablo Arturo; Runkel, Robert L.; Núñez, Jorge; Duhalde, Denisse; Maturana, Hugo; Rojas, Eduardo; Arumí, José L.; Castillo, Daniela; Oyarzún, Ricardo
    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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    Incremental construction: a strategy to facilitate access to housing
    (International Institute for Environment and Development (IIED), 2008) Greene, Margarita; Rojas, Eduardo
    The "enabling" approach to housing markets promotes financing systems based on family savings, public subsidies and mortgage loans to unleash the potential of individuals and communities to produce and improve dwellings. However, the approach failed to benefit lower-income households, as they have less ability to generate savings or make mortgage payments. These households are forced to use informal mechanisms to access housing, such as purchasing land in illegal sub-divisions or squatting on public land and incrementally building their dwellings. The present work argues that supporting the incremental housing construction undertaken by poor households through an enabling approach can make a significant contribution to solving the housing problem in Latin America. The paper discusses the challenges and opportunities in executing this new type of programme, which requires coordinating the resources and capabilities of the beneficiaries with those of the different levels of government and the civil society. While this paper draws on experiences in Latin America and the Caribbean, the proposed approach is also relevant in other settings.
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