Browsing by Author "Brescia-Norambuena, Leonardo"

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    Experimental Analysis of Helix Aspersa Shell as Cementitious Material
    (Springer, 2024) Campos-Cortes, María José; Brescia-Norambuena, Leonardo; Retamoso, Claudia; Escalona Burgos, Néstor Guillermo
    The high environmental impact of the cement industry demands the study of new cementitious materials. Often supplementary cementitious materials such as fly ash or silica fume are used; however, the depletion of raw materials encourages the assessment of new sources. Due to the high calcium content of snail shells, this research explored the use of crushed powder of Helix Aspersa to replace cement, evaluating its use at different percentages of replacement in weight (0, 5, and 10%), calcination temperature (0, 450, and 900 °C) and water-cementitious materials ratios (0.35, 0.40, and 0.45). The results included analysing setting time, compressive and flexural strength, water absorption, and shrinkage. Results indicated that snail shells (i) create an expansion during the first days (~15%), reaching similar values at 28 days, (ii) decrease the water absorption at calcination temperatures ≥450 °C, and (iii) slightly reduce the flexural strength (~16% in average) and compressive strength (~10% in average). As the main decrement of the responses is at a low w/cm ratio, it is expected that calcined snail shells offer the opportunity to save cement and pollution from the construction industry.
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    Improving concrete underground mining pavements performance through the synergic effect of silica fume, nanosilica, and polypropylene fibers
    (2021) Brescia-Norambuena, Leonardo; Gonzalez, Marcelo; Avudaiappan, Siva; Saavedra Flores, Erick, I; Grasley, Zachary
    Concrete pavements for underground mining are in service under very aggressive exposure conditions (heavy loads and chemical attacks), which reduce their service life and affect mining productivity. Aiming to improve the concrete's performance, the combined use of silica fume, nanosilica, and polypropylene fibers was investigated. While each of these materials contributes independently to improving concrete performance, the similar chemistry of nanosilica and silica fume and the considerable workability loss by using each of these materials could negatively impact the concrete properties when used together. Therefore, it is necessary to demonstrate the synergy of using these three materials together, and quantify their relevance in the concrete response. In comparison to the control mix, the concrete mixes with the combined additions showed an average improvement of i) 17% of compressive strength, ii) 23% of splitting strength, and iii) 22% of flexural strength, iv) 200% of the surface resistivity, v) 212% of the abrasion resistance, and vi) 158% of less sulfate expansion. As the numerical modelling of the results indicated a statistically significant interaction between the independent variables, it is proposed that the silica fume, nanosilica, and fibers act synergically, enhancing the underground mining pavements. (C) 2021 Elsevier Ltd. All rights reserved.