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Item type:Publication, Additive construction using enhanced earthen-based composites: Improvement of the mechanical strength and water durability using chitosan and agave fibers(Elsevier Ltd, 2024-01-12)3D printing has emerged as a revolutionary technology with potential applications in the construction industry. However, the prevalent use of ordinary cement in most 3D printing formulations results in significant greenhouse gas emissions during 3D printing construction. In contrast, earthen-based composites are an eco-friendly alternative for building materials. However, as a construction material, earth presents poor mechanical strength and low durability against water erosion. This study aims to obtain earthen-based composites with suitable mechanical and durability properties to investigate their extrudability and buildability in tests. It also explores the effects of incorporating short sisal fibers (l/d ratio = 138.7) and chitosan (DD = 91%, Mw = 598 kDa) to improve strength and water durability in earthen-based composites for 3D printing purposes. Chitosan is a natural macromolecule derived from a waste product from the food industry, whereas sisal fibers are obtained from the Agave sisalana plant. The change in compressive strength was analyzed through uniaxial compression. Water durability was evaluated by measuring the water contact angle, total and capillary water absorption, and accelerated erosion tests. The results indicate that the use of 3.0% (w/v) aqueous solution of chitosan and 1.0% (w/w) of sisal fibers have an important effect on the hardening and water durability properties of earthen-based composites. This study suggests that these materials could serve as natural additives to enhance the mechanical properties and water durability of new eco-friendly construction materials for 3D printing. In conclusion, this study demonstrates that appropriate formulations with natural and eco-friendly additives can lead to stabilized earthen-based composites with suitable printing, mechanical and durability properties for 3D printing applications in construction materials. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Development and characterization of a printable concrete made with construction and demolition waste aggregates(Springer Science and Business Media B.V., 2024-01-01)To address the environmental challenges associated with Construction and Demolition Wastes (CDW) disposal and the depletion of natural sand resources by the construction industry, this paper investigates the potential use of fine aggregates from CDW as a complete replacement for natural sand in concrete formulations tailored for 3D printing applications. The study begins by physically characterizing fine aggregates produced by crushing and sieving CDW from concrete and fired clay brick residues. This stage includes water content and water absorption capacity tests, specific gravity tests and unit weight tests, and particle size analysis. Then, a 3D printable concrete mix formulated entirely with CDW fine aggregates, replacing 100% of natural sand, is developed using mortar flow and rotational rheology tests. This formulation is validated by printing a medium-sized wall using a 3D printing system developed in-house. Finally, compression tests are performed on printed filaments to examine mechanical properties such as compressive strength and modulus of elasticity. Fresh-state and hardened-state properties are compared with control concrete samples made with natural sand (0% of CDW fine aggregates). The study demonstrates the feasibility of formulating printable concretes with a total replacement of sand by CDW for real-size applications. However, special attention must be given in large-scale projects to the rate of workability loss caused by the high water absorption capacity of CDW fine aggregates. The research findings offer valuable insights into the potential and performance of CDW aggregates in 3D-printed concrete applications within the context of a circular economy. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Comprehensive investigation into the influence of soil composition and water content on cracking due to drying shrinkage in 3D-printed earthen structures(Springer Science and Business Media B.V., 2024-01-01)As a raw material for additive construction, earth offers a multitude of benefits, from environmental and economic to social points of view. However, the fresh-state properties of printable materials and the curing conditions of additively manufactured elements make large-scale 3D-printed earthen structures susceptible to suffering severe cracking from shrinkage during drying. This project investigates the effect of soil composition and water content on the development of drying shrinkage cracking in 3D-printed earthen structures. This article presents two strategies for minimizing those cracks: decreasing the clay content of the soil by adding fine sand and decreasing the required water content for printability by using a clay dispersant agent. Earth-based mix designs with different soil/fine-sand ratios and sodium hexametaphosphate (SHMP) contents were subjected to flow table, rotational rheology, and shrinkage cracking tests. The results indicate that the clay and water content are determining factors that minimize the appearance of cracks due to drying shrinkage. Two earthen-based formulations with zero cracks due to shrinkage resulted from replacing 50% wt. of the soil with fine sand and the addition of 0.55 and 2.20% wt. of SHMP. Further research is needed to confirm the validity of these findings across diverse soil types and curing conditions. - 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, Use of organic residues for the mechanical enhancement of sustainable rammed earth(Springer Science and Business Media B.V., 2024-01-01)This research focuses on defining a sustainable rammed earth (RE) material using organic residues. Based on the wide availability and the positive effects on earthen materials, it was decided to incorporate used cooking oil as an organic stabilizer and rice husk as fiber reinforcement to enhance the mechanical properties of RE. Considering these residues, six mix-designs were evaluated with different concentrations of used cooking oil and rice husk. Two additional mix-designs based on unstabilized and cement-based stabilized RE were evaluated for comparison purposes. The optimum water content was defined based on compaction curves obtained with standard proctor tests. The compressive strength of the sustainable RE at different curing conditions was assessed by uniaxial compression tests on cubic samples extracted from the RE walls, and the results were compared with those of an unstabilized and cement-based stabilized RE. Results indicated that using rice husk residue could enhance the compressive strength of RE, obtaining similar strength values to traditional cement-based stabilized RE. On the contrary, used cooking oil samples were characterized by a substantial reduction in compressive strength at ambient curing conditions. However, this negative effect was overcome when oven-induced drying was applied.