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Antico, F. C., Concha-Riedel, J., Valdivia, I., García Herrera, C., & Utrera, A. (2023). The fracture mechanical behavior of the interface between animal fibers, mortar, and earth matrices. A theoretical and experimental approach. Compos. B. Eng., 254, 110568.
Abstract: Theoretical-experimental research is presented to address the mechanics and failure mode of the interface between two matrices with brittle behavior, earth and mortar, and pig hair, an organic fiber that is a massive waste from the food industry worldwide. A comprehensive statistical analysis of the pull-out force is presented, accounting for the effect of fiber embedded length, diameter variability, and age of the matrices. Experimental results are contrasted with fracture-mechanics theories to describe its behavior in this matter. Results show that neither fiber length, variability of diameter, nor the age of the matrix influences the pull-out force of both matrices evaluated in this work. Our results show the brittle nature of these interfaces, which was also observed using a high-speed camera. The tensile load of the fibers was compared to the pull-out force, showing that these fibers always work within their elastic regime. This work contributes directly to the sustainable goals 9, 11, and 15 enacted by the United Nations in 2015, by contributing to the understanding of the fracture mechanics of a waste product used as reinforcement of construction matrices.
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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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Concha-Riedel, J., Antico, F. C., & Lopez-Querol, S. (2021). Mechanical strength, mass loss and volumetric changes of drying adobe matrices combined with kaolin and fine soil particles. Constr. Build. Mater., 312, 125246.
Abstract: Earthen construction represents almost 30% of the housing in developing countries, partially because of its low cost compared to steel and concrete construction, and also because the raw materials are available almost everywhere. One of the biggest disadvantages of earthen materials is the lack of information and variety on their constitutive materials, specifically their soil type. This work addresses the physical and mechanical properties of adobe matrices containing different concentrations of kaolin, which is a specific type of clay, as well as different proportions of fine particles of the original soil of the adobe matrix. All adobe matrices were manufactured with a SM-SC soil obtained from Santiago, Chile, and had concentrations of 0, 10, 30, and 50% of kaolin and 0, 10, 20, and 30% fines of the original soil content. It is concluded that the compressive strength of the studied earthen mixtures improves when kaolin is added to the mixture. The shrinkage of adobe matrices with kaolin compared to plain adobe matrices was reduced during the first days of age and stayed stable after that. This work shows that the inclusion of fines from the original soil (other than kaolin) did not significantly affect any of the studied properties. It also shows that the Unified Soil Classification System is not sufficient to characterize soils for adobe matrices.
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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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