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    Item type:Publication,
    Fiber–matrix interaction governs compressive strength in agave-bagasse-reinforced adobe: a factorial experiment with two-way ANOVA and competing mechanism analysis
    (Frontiers Media SA, 2026-07-31)
    De-Obaldia-Escalante, Marcela
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    Del-Valle-Soto, Carolina
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    Acevedo-Parra, H. R.
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    Montoya-Márquez, Orlando
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    Natural-fiber reinforcement is widely cited as a pathway to improve the mechanical performance of adobe, but reported effects on compressive strength are inconsistent across studies: some find improvement, others find degradation, and the choice of experimental conditions rarely disentangles the role of the fiber from that of the matrix. This study quantifies the coupling through a balanced factorial experiment. Forty-nine adobe specimens of (Formula presented) cm were manufactured with three granular compositions (sand-dominated, jal-dominated, and balanced, where jal is a regional non-plastic silt of Jalisco, Mexico) and four mass fractions of agave-bagasse fiber (0%, 0.5%, 1%, and 2%), and were tested under Mexican standard NMX-C-036-ONNCCE by an accredited external laboratory. Three complementary analytical tools are applied to the resulting dataset: (i) a two-way analysis of variance (ANOVA), (ii) a reinforcement efficiency index (Formula presented) with bootstrap confidence intervals, and (iii) a competing mechanism phenomenological descriptor (Formula presented) that separates a saturating reinforcement term from a linear disruption term. The two-way ANOVA reveals a highly significant mixture–fiber interaction ((Formula presented), (Formula presented), and partial (Formula presented)), which is stronger than either main effect and statistically demonstrates that the sign of the fiber effect is not an intrinsic property of the fiber but rather a property of the fiber–matrix pair. For sand-containing mixtures, the reinforcement efficiency index is (Formula presented) [M1, 95% bootstrap CI (0.96, 1.32)] and (Formula presented) [M3, (0.92, 1.59)] at the optimum (Formula presented); a non-parametric bootstrap over 5, 000 resamples places the optimum at (Formula presented) with posterior probability (Formula presented) (M1) and (Formula presented) (M3). For the jal-dominated mixture, fiber inclusion is net destructive [(Formula presented), (0.68, 0.95) at (Formula presented)], with Welch (Formula presented)-tests rejecting equivalence with the control at (Formula presented) (0.5%) and (Formula presented) (2%) and Cohen’s effect sizes (Formula presented). The best-performing conditions yield mean compressive strengths of 3.22 MPa, which exceeds the 2.0 MPa minimum required by NMX-C-441-ONNCCE-2011 for non-structural masonry by 60%. An immersion test shows that unstabilized specimens disintegrate within 2–3 min, bounding applications to non-exposed or externally protected uses and defining the primary direction for future work.
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    Item type:Publication,
    Experimental analysis of ecuadorian adobe reinforced with natural fibers
    (2025)
    Carlos Pinto-Almeida
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    ;
    Nahomy Anahí Armas-Robalino
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    Bianca Christina Cáceres
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    Juan Carlos Cajas-Corrales
    Introduction: In Latin America, the use of adobe as a building material remains highly relevant due to its low cost, local availability, and low environmental impact. Nevertheless, its limited mechanical strength and lack of standardization constrain broader implementation in contemporary architecture. Methods: This study addresses that gap by experimentally evaluating the mechanical performance of adobe blocks stabilized with fine sand and wild straw, produced with red clay from Puyo (Ecuador). The research followed an applied, descriptive–comparative design encompassing material characterization, a 30-day natural curing process, and compressive strength testing using a SHIMADZU Concreto 2000X machine. Results: The stabilized blocks achieved an average compressive strength of 9.63 kg/cm² (≈ 0.94 MPa), a mean displacement of 2.98 mm, and a maximum load of 14.16 kN, values that confirm their suitability for low-rise load-bearing structures. The inclusion of wild straw improved ductility, internal cohesion, and post-fracture integrity, while controlled shade drying minimized microcracking. Compared with traditional handmade bricks (31 kg/cm²), the material showed lower strength but significantly higher environmental and economic sustainability. Conclusion: The results provide empirical indicators to guide the standardization and scalability of stabilized adobe as a low-carbon, structurally viable alternative for rural and peri-urban housing in seismic regions.
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