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Antico, F. C., Rojas, P., Briones, F., & Araya-Letelier, G. (2021). Animal fibers as water reservoirs for internal curing of mortars and their limits caused by fiber clustering. Constr. Build. Mater., 267, 120918.
Abstract: We present a bottom-up experimental research to address evidence of internal curing of mortars using randomly distributed pig-hair as water reservoirs. Plain and reinforced mortars with pig hair ranging from 0 to 8 kg of fibers per cubic meter of mortar were prepared. The microstructures of plain and reinforced mortars were scanned using electron microscopy and the microhardnesses were measured within
the bulk cement paste and cement paste near pig fibers. Electrical resistivity, surface absorption, and residual compressive strength of mortars after freeze-thaw cycles were used to test the effects of internal curing caused by pig hair. Natural fibers used to reinforce mortars increase their toughness and provide
part of the necessary water for internal curing, yet internal curing originated by the addition of natural fibers is not proportional to fiber dosage; where the potential to form fiber clusters increases as fiber dosage increases. Results show that there is an optimum fiber dosage that maximizes internal curing
caused by these fibers. This study contributes to the research on reinforced mortars with natural fibers to provide sustainable solutions for construction materials.
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Antico, F. C., Wiener, M. J., Araya-Letelier, G., & Retamal, R. G. (2017). Eco-bricks: a sustainable substitute for construction materials. Rev. Constr., 16(3), 518–526.
Abstract: Eco-bricks, polyethylene terephthalate (PET) bottles filled with mixed inorganic waste, have become a low cost construction material and a valid recycling method to reduce waste disposal in regions where industrial recycling is not yet available. Because Eco-bricks are filled with mixed recovered materials, potential recycling of its constituents is difficult at the end of its life. This study proposes considering Eco-bricks filled with a single inorganic waste material to work as a time capsule, with potential for recovering the filling material when other ways of waste valorization are available within those communities that currently have no better recycling options. This paper develops an experimental characterization of density, filler content (by volume), thermal shrinkage, elastic modulus and deformation recovery capacity using four different filler materials: 1) PET; 2) paper & cardboard; 3) tetrapack; and 4) metal. Overall, Eco-brick's density, thermal shrinkage and elastic modulus are dependent on the filler content. Density and elastic modulus of the proposed Eco-bricks are similar to values of medium-high density expanded polystyrene (EPS) used in nonstructural construction, reason why we suggest that these Eco-bricks might be a sustainable alternative to EPS or other nonstructural construction materials.
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Araya-Letelier, G., Antico, F. C., Burbano-Garcia, C., Concha-Riedeld, J., Norambuena-Contreras, J., Concha, J., et al. (2021). Experimental evaluation of adobe mixtures reinforced with jute fibers. Constr. Build. Mater., 276(2021), 122127.
Abstract: Due to their sustainability as well as physical and mechanical performance, different natural fibers, both vegetal and animal fibers, have been successfully used in adobe mixtures (AMs) to enhance properties such as cracking control, flexural toughness and water erosion resistance, among others. However, the use of jute fibers (JFs), one of the most largely produced vegetal fiber worldwide, has not been extensively studied on AMs. Consequently, this study evaluates the effects of the incorporation of varying dosages (0.5 and 2.0 wt%) and lengths (7, 15, and 30 mm) of JFs on the physical/thermal/mechanical/fracture and durability performance of AMs, a specific type of earth-based construction material widely used globally. Experimental results showed that the incorporation of 2.0 wt% dosages of JFs increased the capillary water absorption of AMs, which might affect AM durability. The latter result could be explained by the additional porosity generated by the spaces left between the JFs and the matrix of adobe, as well as the inherent water absorption of the JFs. The incorporation of JFs significantly improved the behavior of AMs in terms of thermal conductivity, drying shrinkage cracking control, flexural toughness and water erosion performance, without affecting their compressive and flexural strength. For example, flexural toughness indices were increased by 297% and crack density ratio as well as water erosion depth values were reduced by 93% and 62%, respectively, when 2.0 wt%-15 mm length JFs were incorporated into AM. Since the latter combination of JF dosage and length provided the overall best results among AMs, it is recommended by this study as JF-reinforcement scheme for AMs for construction applications such as adobe masonry and earth plasters.
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Araya-Letelier, G., Antico, F. C., Carrasco, M., Rojas, P., & Garcia-Herrera, C. M. (2017). Effectiveness of new natural fibers on damage-mechanical performance of mortar. Constr. Build. Mater., 152, 672–682.
Abstract: Addition of fibers to cement-based materials improve tensile and flexural strength, fracture toughness, abrasion resistance, delay cracking, and reduce crack widths. Natural fibers have recently become more popular in the construction materials community. This investigation addresses the characterization of a new animal fiber (pig hair), a massive food-industry waste worldwide, and its use in mortars. Morphological, physical and mechanical properties of pig hair are determined in order to be used as reinforcement in mortars. A sensitivity analysis on the volumes of fiber in mortars is developed. The results from this investigation showed that reinforced mortars significantly improve impact strength, abrasion resistance, plastic shrinkage cracking, age at cracking, and crack widths as fiber volume increases. Other properties such as compressive and flexural strength, density, porosity and modulus of elasticity of reinforced mortars are not significantly affected by the addition of pig hair. (C) 2017 Elsevier Ltd. All rights reserved.
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Araya-Letelier, G., Concha-Riedel, J., Antico, F. C., & Sandoval, C. (2019). Experimental mechanical-damage assessment of earthen mixes reinforced with micro polypropylene fibers. Constr. Build. Mater., 198, 762–776.
Abstract: The addition of engineered polypropylene fibers to earthen materials offers new opportunities to control their damage evolution and mechanical properties that altogether provides more reliability and extends the life span of these materials. The latter is of special interest considering that earthen materials are still widely used in the form of adobe blocks for earthen masonry, cob, rammed earth or even earthen mortars for new construction and conservation of historic buildings. In this work, the effect of dosage of micro polypropylene fibers (MPPF) in the damage-mechanical performance of earthen mixes is studied experimentally. Part of the experiments includes two different tests to assess distributed and localized cracking of reinforced earth subject to restrained drying shrinkage. In addition, the experimental results showed that the incorporation of MPPF increases up to 83 times the impact strength and 11 times the flexural toughness of earthen mixes. Other mechanical properties such as compressive and flexural strength are not statistically affected by the incorporation of MPPF. (C) 2018 Elsevier Ltd. All rights reserved.
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Araya-Letelier, G., Concha-Riedel, J., Antico, F. C., Valdes, C., & Caceres, G. (2018). Influence of natural fiber dosage and length on adobe mixes damage-mechanical behavior. Constr. Build. Mater., 174, 645–655.
Abstract: This study addresses the use of a natural fiber (pig hair), a massive food-industry waste, as reinforcement in adobe mixes (a specific type of earthen material). The relevance of this work resides in the fact that earthen materials are still widely used worldwide because of their low cost, availability, and low environmental impact. Results show that adobe mixes' mechanical-damage behavior is sensitive to both (i) fiber dosage and (ii) fiber length. Impact strength and flexural toughness are increased, whereas shrinkage distributed crack width is reduced. Average values of compressive and flexural strengths are reduced as fiber dosage and length increase, as a result of porosity generated by fiber clustering. Based on the results of this work a dosage of 0.5% by weight of dry soil using 7 mm fibers is optimal to improve crack control, flexural toughness and impact strength without statistically affecting flexural and compressive strengths. (C) 2018 Elsevier Ltd. All rights reserved.
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Araya-Letelier, G., Maturana, P., Carrasco, M., Antico, F. C., & Gomez, M. S. (2019). Mechanical-Damage Behavior of Mortars Reinforced with Recycled Polypropylene Fibers. Sustainability, 11(8), 17 pp.
Abstract: Commercial polypropylene fibers are incorporated as reinforcement of cement-based materials to improve their mechanical and damage performances related to properties such as tensile and flexural strength, toughness, spalling and impact resistance, delay formation of cracks and reducing crack widths. Yet, the production of these polypropylene fibers generates economic costs and environmental impacts and, therefore, the use of alternative and more sustainable fibers has become more popular in the research materials community. This paper addresses the characterization of recycled polypropylene fibers (RPFs) obtained from discarded domestic plastic sweeps, whose morphological, physical and mechanical properties are provided in order to assess their implementation as fiber-reinforcement in cement-based mortars. An experimental program addressing the incorporation of RPFs on the mechanical-damage performance of mortars, including a sensitivity analysis on the volumes and lengths of fiber, is developed. Using analysis of variance, this paper shows that RPFs statistically enhance flexural toughness and impact strength for high dosages and long fiber lengths. On the contrary, the latter properties are not statistically modified by the incorporation of low dosages and short lengths of RPFs, but still in these cases the incorporation of RPFs in mortars have the positive environmental impact of waste encapsulation. In the case of average compressive and flexural strength of mortars, these properties are not statistically modified when adding RPFs.
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Araya-Letelier, G., Parra, P. F., Lopez-Garcia, D., Garcia-Valdes, A., Candia, G., & Lagos, R. (2019). Collapse risk assessment of a Chilean dual wall-frame reinforced concrete office building. Eng. Struct., 183, 770–779.
Abstract: Several code-conforming reinforced concrete buildings were severely damaged during the 2010 moment magnitude (M-w) 8.8 Chile earthquake, raising concerns about their real collapse margin. Although critical updates were introduced into the Chilean design codes after 2010, guidelines for collapse risk assessment of Chilean buildings remain insufficient. This study evaluates the collapse potential of a typical dual system (shear walls and moment frames) office building in Santiago. Collapse fragility functions were obtained through incremental dynamic analyses using a state-of-the-art finite element model of the building. Site-specific seismic hazard curves were developed, which explicitly incorporated epistemic uncertainty, and combined with the collapse fragility functions to estimate the mean annual frequency of collapse (lambda(c)) values and probabilities of collapse in 50-years (P-c(50)). Computed values of lambda(c) and P-c(50) were on the order of 10(-5)-10(-4), and 0.1-0.7%, respectively, consistent with similar studies developed for buildings in the US. The results also showed that the deaggregation of lambda(c) was controlled by small to medium earthquake intensities and that different models of the collapse fragility functions and hazard curves had a non-negligible effect on lambda(c) and P-c(50), and thus, propagation of uncertainty in risk assessment problems must be adequately taken into account.
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Caceres, G., Nasirov, S., Zhang, H. L., & Araya-Letelier, G. (2015). Residential Solar PV Planning in Santiago, Chile: Incorporating the PM10 Parameter. Sustainability, 7(1), 422–440.
Abstract: This paper addresses an economic study of the installation of photovoltaic (PV) solar panels for residential power generation in Santiago, Chile, based on the different parameters of a PV system, such as efficiency. As a performance indicator, the Levelized Cost of Energy (LCOE) was used, which indicates the benefit of the facility vs. the current cost of electrical energy. In addition, due to a high level of airborne dusts typically associated with PM10, the effect of the dust deposition on PV panels' surfaces and the effect on panel performance are examined. Two different scenarios are analyzed: on-grid PV plants and off-grid PV plants.
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Carrasco, M., Araya-Letelier, G., Velazquez, R., & Visconti, P. (2021). Image-Based Automated Width Measurement of Surface Cracking. Sensors, 21(22), 7534.
Abstract: The detection of cracks is an important monitoring task in civil engineering infrastructure devoted to ensuring durability, structural safety, and integrity. It has been traditionally performed by visual inspection, and the measurement of crack width has been manually obtained with a crack-width comparator gauge (CWCG). Unfortunately, this technique is time-consuming, suffers from subjective judgement, and is error-prone due to the difficulty of ensuring a correct spatial measurement as the CWCG may not be correctly positioned in accordance with the crack orientation. Although algorithms for automatic crack detection have been developed, most of them have specifically focused on solving the segmentation problem through Deep Learning techniques failing to address the underlying problem: crack width evaluation, which is critical for the assessment of civil structures. This paper proposes a novel automated method for surface cracking width measurement based on digital image processing techniques. Our proposal consists of three stages: anisotropic smoothing, segmentation, and stabilized central points by k-means adjustment and allows the characterization of both crack width and curvature-related orientation. The method is validated by assessing the surface cracking of fiber-reinforced earthen construction materials. The preliminary results show that the proposal is robust, efficient, and highly accurate at estimating crack width in digital images. The method effectively discards false cracks and detects real ones as small as 0.15 mm width regardless of the lighting conditions.
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Cataldo-Born, M., Araya-Letelier, G., & Pabon, C. (2016). Obstacles and motivations for earthbag social housing in Chile: energy, environment, economic and codes implications. Rev. Constr., 15(3), 17–26.
Abstract: Chile presents a social housing deficit that needs to be addressed with solutions that increase habitability and environmental benefits. This paper addresses the benefits of implementing earthbag buildings as an option to mitigate the existing social housing deficit in Chile. A literature review presents details on the use of earthbag buildings around the world, and motivations and obstacles for implementing earthbag buildings in Chile. In particular, a case study was simulated to compare an earthbag social house to a reinforced brick masonry social house in terms of environmental and economic performances such as CO2 emissions, energy and costs. It is concluded that both alternatives generate similar CO2 emissions, but the earthbag social house can save up to 20% of energy during its life cycle. In economic terms, the earthbag social house generates savings of 50% and 38% for initial investment and life cycle cost, respectively, compared to the reinforced brick masonry social house. The implementation of earthbag social housing projects would be encouraged by the development of a Chilean building code for earthbag design that provides guidance on the safe use of this technique in a seismic country.
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Concha-Riedel, J., Antico, F.C., Araya-Letelier, G. (2020). Mechanical and damage similarities of adobe blocks reinforced with natural and industrial fibres. Materia, 25(4), 11pp.
Abstract: Adobe is an earthen-based material that consists of the use of a clayey soil and, most of the times, straw fibres to manufacture blocks that are afterwards sundried. This study reviews the use of three types of fibres:
vegetal, industrial and animal, for the manufacture of adobe blocks. Overall, all the fibres increase at least one order of magnitude the impact strength of plain adobe blocks and reduced the shrinkage cracking of adobe plasters in at least 50% with respect to plain adobe. Compressive and flexural strength average values were not increased nor decreased by the addition of fibres. The intrinsic variability of the mechanical properties of plain adobe persists with any of the fibres tested in this study. Based on the findings of this study, we recommend using jute fibres with a dosage of 0.5% and a length of 30 mm.
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Fullenkamp, K., Montane, M., Caceres, G., & Araya-Letelier, G. (2019). Review and selection of EPCM as TES materials for building applications. Int. J. Sustain. Energy, 38(6), 561–582.
Abstract: In order to improve the thermal efficiency of building thermal energy storage (TES) systems, the feasibility of using encapsulated phase change materials (EPCMs) as heat storage media is analysed in this work. Specifically, the finite element method is used to perform thermal behaviour analyses of several EPCMs. These analyses include technical and economic assessments in order to identify the best combination of PCM and shell material, using as main parameters: thermal energy storage, heat transfer rate, materials cost, among others. The results show that EPCMs composed by Na2SO4 center dot 6H(2)O as PCM and covered by stainless steel highlight as TES materials.
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Gallegos, M. F., Araya-Letelier, G., Lopez-Garcia, D., & Parra, P. F. (2023). Collapse Assessment of Mid-Rise RC Dual Wall-Frame Buildings Subjected to Subduction Earthquakes. Buildings, 13(4), 880.
Abstract: In Chile, office buildings are typically reinforced concrete (RC) structures whose lateral load-resisting system comprises core structural walls and perimeter moment frames (i.e., dual wall-frame system). In the last 20 years, nearly 800 new dual wall-frame buildings have been built in the country and roughly 70% of them have less than ten stories. Although the seismic performance of these structures was deemed satisfactory in previous earthquakes, their actual collapse potential is indeed unknown. In this study, the collapse performance of Chilean code-conforming mid-rise RC buildings is assessed considering different hazard levels (i.e., high and moderate seismic activity) and different soil types (i.e., stiff and moderately stiff). Following the FEMA P-58 methodology, 3D nonlinear models of four representative structural archetypes were subjected to sets of Chilean subduction ground motions. Incremental dynamic analysis was used to develop collapse fragilities. The results indicate that the archetypes comply with the 'life safety' risk level defined in ASCE 7, which is consistent with the observed seismic behavior in recent mega-earthquakes in Chile. However, the collapse risk is not uniform. Differences in collapse probabilities are significant, which might indicate that revisions to the current Chilean seismic design code might be necessary.
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Gallegos, M. F., Araya-Letelier, G., Lopez-Garcia, D., & Parra, P. F. (2023). Seismic collapse performance of high-rise RC dual system buildings in subduction zones. Case Stud. Constr. Mater., 18, e02042.
Abstract: The satisfactory 'collapse prevention' performance level of reinforced concrete (RC) buildings has been widely recognized during recent earthquakes in Chile. However, there is limited research on the actual level of seismic collapse protection. In this study, the seismic collapse behavior of high-rise RC dual wall-frame buildings representative of the Chilean inventory is quantitatively eval-uated. A suite of four 16-story structural archetypes was carefully selected and code-based designed assuming two different locations (i.e., high and moderate seismicity zones) and two different soil types (i.e., very stiff and moderately stiff soils). The archetypes were analyzed considering the latest developments in performance-based earthquake engineering implementing incremental dynamic analyses for 3D nonlinear models with sets of Chilean subduction ground motions. Results, expressed in terms of the probability of collapse conditioned on the Maximum Considered Earthquake (MCE) hazard level (<10%) and the collapse probability in 50 years (<1%), showed that all archetypes fully met the targets specified by ASCE 7 for an acceptable 'life safety' risk level. These results indeed explain why a very small number of RC building collapses was observed in the recent megathrust earthquakes (Mw>8.0) in Chile. Nevertheless, it was also found that the seismic collapse performance is not uniform, due mainly to the soil type. This observation suggests that the design spectra indicated by the Chilean seismic design code for buildings might need to be revised.
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