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Item type:Publication, Non-destructive (NDT) and minor-destructive (MDT) testing tools to support the structural characterization of adobe constructions(Springer Nature, 2021-01-01)Adobe constructions are widely used worldwide as low-cost vernacular buildings and also as monuments and historical constructions. Beside low cost these materials have excellent thermal and acoustic properties. Some challenges of this material involves durability and high vulnerability to seismic motions due to its relatively high weight and brittleness. To improve safety levels of existing adobe structures it is often necessary to strengthen or retrofit them based on a structural characterization. The structural characterization requires assessment of the in situ condition, geometry, engineering properties of existing adobe construction and buildings using minimal to no intrusion. In this chapter we present a general overview of commonly used NDT and MDT methods for the assessment of existing adobe construction to obtain information such as: detailed geometry information, damage mapping, and multi-scale mechanical and physical characterization. Additional to literature review summarizing different applications of NDT and MDT, this chapter presents four case studies related to projects in Peru recently performed by the research group led by the first author. The descriptions and results of NDT and MDT tests carried out at these case studies highlight how the use of several NDT and MDT methodologies complement each other and allow a suitable multi-scale characterization of existing adobe structural systems, that can successfully be used for the diagnosis, and design of intervention and retrofit measures as needed. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Specific dissipated energy as a failure predictor for uniform sands under constant volume cyclic simple shear loading(Springer Science+Business Media, 2021-10-27)An experimental study was performed to investigate the dissipated energy to failure of sand samples subjected to uniform and non-uniform cyclic simple shear loading. The hypothesis evaluated was that for a given initial sample state the specific dissipated energy required to reach failure should be reasonably constant independent of the type of stress-time history used in the testing. Test samples consisted of dry Ottawa sand prepared at nine different initial states that were subjected to different stress controlled cyclic horizontal shear loading waveforms that included 15 uniform sinusoidal waves and up to 33 non-uniform loading wave forms. The experimental program presented showed that the measured cumulative dissipated specific energy to failure, defined when the double amplitude shear strain reaches 7.5%, for the different sample initial states was reasonably constant but with coefficients of variation ranging between 13 to 44%. As expected, the cumulative dissipated energy increased with increasing initial stress level and relative density. The findings support the notion that specific dissipated energy can be used as a reasonable failure predictor for uniform dry sands based on their initial state and are independent of the type of cyclic simple shear loading waveform using in the testing. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, A simplified method to predict failure of sands under general cyclic simple shear loading(ICE Publishing, 2022-06-16)This paper describes a simplified approach based on constant-volume cyclic simple shear (CSS) tests with uniform sinusoidal loading that can predict failure of dry sands under general shear stress–time histories. The simplified method is based on the cumulative energy hypothesis that states that the dissipated energy required by a sand sample to reach failure depends only on its initial state (D r and [Formula: see text]) and is independent of the characteristics of the cyclic loading applied. The proposed method uses a sand-specific multivariable regression developed using a small number of CSS tests involving uniform sinusoidal loading without the need for advanced general cyclic loading tests. Furthermore, the regression requires only a small data set involving one uniform CSS test per sample initial state. The simplified method was evaluated using two comprehensive experimental studies involving two different test sands. The first data set is an experimental programme by the authors involving 20/30 Ottawa sand subjected to different cyclic loading types. The second data set is an independent experimental programme that used 0/30 Monterey sand. In both cases, the simplified approach was found to yield reasonable predictions of failure of the test sands when subjected to complex and irregular shear stress loading. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Eco-friendly additive construction: Analysis of the printability of earthen-based matrices stabilized with potato starch gel and sisal fibers(Elsevier Ltd, 2022-09-12)3D printing for construction purposes is a disruptive technology with the potential for rapid and massive applications making it a feasible alternative for social housing, temporary shelters after disasters, and, recently, for extraterrestrial habitats. However, most of the matrices used for construction by 3D printing are based on hydraulic cement as the main constituent, which is not easily available in remote locations and is an important greenhouse gases generator. Therefore, a good understanding to formulate and evaluate alternative matrices using soil and organic materials with the required fresh and hardened-state properties compatible with this emerging technology is needed. This article studies the printable capabilities of eco-friendly earthen-based matrices which uses potato starch as a natural stabilizer for raw soil mortars aiming to obtain 3D printed filaments with adequate fresh and hardened-states properties. The aqueous starch gel was combined with sisal fibers in the printing mixture to control shrinkage cracking problems during hardening. The optimization of the dosage of the stabilizer was carried out considering different tests in fresh and hardened printed filaments namely, pumpability and extrudability, stacking, shear vane, shrinkage cracking, Vicat needle, compression strength, and capillarity absorption tests. The results indicate that printable earthen-based matrices reinforced with 1 % of sisal fibers by weight of soil and stabilized with aqueous starch gels with concentrations up to 5 % (w/w) showed improved workability and minor cracking and can be used for 3D printing. These promising results in the field of material science combined with novel 3D printing technology that is also presented in the article open new lines of research for eco-friendly alternatives for the construction industry. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Additive construction of concrete deep beams using low-cost characterization methods and FEM-based topological optimization(Elsevier Ltd, 2024-03-08)Additive manufacturing using concrete for large-scale construction purposes has demonstrated economic, social, and environmental benefits compared to conventional building procedures. These advantages stem from the capabilities of concrete 3D printing, which facilitates a rapid, accurate, and low-waste construction process with substantially less labor and energy requirements compared to traditional casting procedures such as formwork fabrication and stripping, concrete pouring, and concrete consolidation. This technology can pave the way for sustainable and cost-effective housing solutions when coupled with low-carbon concrete formulations and optimized structural designs. However, scientific and industrial experiences have shown that formulating printable concrete requires extensive testing and costly equipment to reach appropriate fresh and hardened-state properties. Therefore, accessible and practical mix-design protocols for the evaluation of printable concrete formulation are needed to enable in-situ control and broader adoption of 3D printing. Once a printable material is developed, innovative design methods, such as topology optimization, that exploit robot-controlled construction to fabricate efficient, safe, and free-form elements can be explored. In this context, this article presents a methodology based on a set of low-cost and accessible experimental tests to develop cement-based matrices with low binder content suitable for layer-by-layer deposition. Furthermore, a framework to design and fabricate efficient structural elements based on numerical-based topological optimization and concrete additive manufacturing is proposed and validated. The systematic experimental campaign carried out indicates that the yield strength obtained from shear vane tests, initially designed for geotechnical field tests, is a reliable reference value for proportioning extrudable, pumpable, and buildable concretes. Employing the proposed framework, four formulations with excellent printing capabilities are presented. These formulations are successfully utilized for additive manufacturing of a topologically optimized deep beam, achieving a remarkable 52% mass reduction compared to a solid element. This showcases the possibility of 3D printing structurally efficient elements with intricate geometries while minimizing material usage, all without the need for formworks.Principio del formulario. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Soil-Cement Matrices for Additive Construction: 3D Printing System Validation and Printing Tests(Trans Tech Publications Ltd, 2023-01-01)Soil as a building material is gaining renewed interest from academia, and the constructionsector, mainly for fabricating low-environmental impact homes. The fabrication of houses with soilusing traditional methods such as adobe, cob, and rammed earth dates back to ancient times. However, emerging construction technologies, such as 3D printing, can be compatible with this material for building purposes. The article presents the validation of a 3D printing system for construction applications and the evaluation of soil-cement matrices' printability. First, the paper defines the printing parameters through experimental testing on soil matrices. Then, the article evaluates the printability of soil-cement matrices through filament printing and stacking tests. The results show that the 3D printing system prototype can fabricate small and medium-sized elements with soil matrices after correctly defining the pumping speed, printing speed, and layer height. Furthermore, experimental printing test results demonstrate that soil-cement matrices can be easily extruded and stacked; however, their printability capacity is strongly affected by the total water content and printing speed. This research highlights the suitability of soil-cement mixtures for additive manufacturing, a promising outcome that can facilitate the construction of homes in remote areas using 3D printing systems. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Preliminary Experimental Evaluation of Buildability Improvement Methods for Concrete for 3D Printing(Trans Tech Publications Ltd, 2023-01-01)3D concrete printing is an innovative construction process based on fully auto nomousmaterial deposition. One of the challenges of implementing this technology is the development of printable concrete formulations, as this material must exhibit particular fresh-state properties. Among these, buildability is one of the most important. This property describes the material's ability to support weight at very early ages, allowing a layer-by-layer construction. Therefore, this paper aims to evaluate two approaches for improving concrete buildability: the optimization of the super plasticizer dosage and the external application of quick-setting admixture. The results showed that reducing super plasticizer content improved buildability by increasing the static yield strength.However, this approach has a collateral disadvantage as concretes presented problems duringextrusion. On the other hand, the results of cylinder stability and Vicat tests indicate that the external application of quick-setting admixture leads to concretes with improved buildability without affecting the initial workability and a faster hardening process. According to these results, the latter approachcan potentially be applied in small and large-scale 3D printing. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Evaluation of Chitosan and Potato Starch as Stabilizers to Improve the Mechanical and Water Durability Properties of Printable Earth-Based Matrices Reinforced with Sisal Fibers(Trans Tech Publications Ltd, 2023-01-01)Due to economic, sustainable, and aesthetic benefits, academia and the construction industry are exploring the use of earth in modern construction is being widely studied. Unfortunately, earth as a construction material has low mechanical, poor water durability resistance, and the potential to swell and crack. Therefore, this paper evaluates chitosan and potato starch, natural biodegradable polymers, as stabilizers to improve mechanical strength and water durability resistance of printable earth-based matrix reinforced with sisal fibers. Although the test results indicated that the chitosan had a better performance as an earth stabilizer than potato starch, adding both stabilizers resulted in earthen composites with higher compressive strength and lower water permeability. These results demonstrate the feasibility of using natural stabilizers to improve the performance of earth-based materials for 3D printing without affecting their printability capacities. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Additive Construction Using Enhanced Earthen-Based Composites: Improvement of the Mechanical Strength and Water Durability Using Chitosan and Agave Fibers(RELX Group (Netherlands), 2023-01-01)