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Item type:Publication, Optimization of a reinforced geopolymer composite using natural fibers and construction wastes(Elsevier, 2020-10-20)Geopolymer technology has allowed the development of eco-friendly construction materials with high mechanical properties using industrial wastes and residues. However, geopolymers show fragility and low ductility behavior similar to Portland cement-based materials. This article focuses on the evaluation of jute and sisal fibers as reinforcement of a geopolymer matrix produced from residues of Fired Clay Brick Powder (FCBP). Control samples with no fibers and reinforced matrices with different contents of jute (ranging from 0.5 to 2.0 wt%) and sisal fibers (ranging from 0.5 to 3.0 wt%) were produced to study the effect of the fiber type and content on the mechanical properties of the resulting geopolymer composites. Mechanical characterization consisted of compression, splitting tensile, and three-point bending tests. The results of compression and splitting tensile tests showed the existence of an optimum fiber content that depends on the fiber type for reaching the maximum strength while the three-point bending test results indicated a linear relationship between the flexural strength and the fiber content. The addition of 2.5% (wt%) of sisal fibers increased the compressive, splitting tensile and flexural strengths up to 76%, 112%, and 270%, respectively, in comparison to the control samples. On the other hand, FCBP-based geopolymers with 1.5% (wt%) jute fiber reinforcement showed an increase up to 64%, 45%, and 222% of the compressive, splitting tensile and flexural strengths, respectively. Both, jute and sisal fiber addition at the optimum content, lead to a change in the failure mode of the samples from a brittle to a more ductile failure in all mechanical tests. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Production of a lightweight masonry block using alkaline activated natural pozzolana and natural fibers(Elsevier, 2020-08-30)Lightweight geopolymers are alternative low-carbon footprint building materials with high potential to produce value added products for the construction industry such as low-density masonry units. This work focuses on presenting the development of a new lightweight masonry block using natural pozzolana-based geopolymer mortar, hydrogen peroxide as a foaming agent and jute fibers as reinforcement additive. The experimental plan allowed the optimization of the production process and the definition of the optimum quantities of hydrogen peroxide content, pozzolana: fine aggregate ratios and the appropriate amount of fibers to be incorporated. The experimental results demonstrate the feasibility of the production of new masonry units, which can achieve up to 8.1 MPa of compressive strength after 28 days of fabrication with reduced bulk densities of 1269 kg/m3. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Mechanical characterization of a masonry system made of alkaline activated pozzolana blocks(Trans Tech Publications Ltdttp@transtec.ch, 2020-01-01)The development of alkaline activated materials has enabled the production of eco-friendly alternatives for the construction industry. In the present article, the mechanical characterization of a new structural masonry system composed of fiber-reinforced lightweight pozzolana-based blocks and cement-lime mortar was performed. The mechanical characterization involved uniaxial compression tests in prisms and diagonal compression in wallets. The results indicate that the compressive and shear strength of the masonry system is up to 3.24 MPa and 0.38, respectively. The results obtained indicate that the evaluated system is structurally efficient and that can be used as both non-load and load-bearing walls. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Bioactive membranes of polymeric micro and nanocomposites prepared with the natural anionic marine polysaccharide (Alginate) functionalized with extracts of cat’s claw (Uncaria tomentosa) and Aloe vera(Trans Tech Publications Ltdttp@transtec.ch, 2020-01-01)In this research, the nanostructured alginate (AL) membranes were prepared with natural bioactive compound, Cat's claw (Uncaria tomentosa) extract (UT). UT is broadly used as an anti-inflammatory agent and the effect on the treatment of Rheumatism was proved by many scientists. For this reason, we added this bioactive compound in the process of AL membrane formulation to improve the biological activities. 2-dimentional (2-D) and 3-dimentional (3-D) AL membranes were prepared with and without addition of UT extracts. 3-D AL membranes were prepared using ultrasound with high intensity. The wettability of AL membranes depending on the concentration of AL was studied by measuring contact angle and surface energy. Stabilization agent, poloxamer 407, was used to improve the stability of AL nanoemulsion. The effects of UT in 3-D AL membranes were studied by measuring swelling behavior and contact angle. The surface morphology was measured with scanning electron microscopy (SEM). Comparing to 2-D AL membranes, 3-D AL membranes presented rougher surface due to AL nanoparticles presence. When UT was incorporated in AL membranes, strong antioxidant activity and higher contact angle and swelling ratio were observed than non-UT incorporated AL membranes. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Study of the Acetylation Pattern of Chitosan by Pure Shift NMR(American Chemical Society, 2020-09-15)Chitosan is a biodegradable, antibacterial, and nontoxic biopolymer used in a wide range of applications including biotechnology, pharmacy, and medicine. The physicochemical and biological properties of chitosan have been associated with parameters such as the degree of polymerization (DP) and the fraction of acetylation ( F A ). New methods are being developed to yield chitosans of specific acetylation patterns, and, recently, a correlation between biological activity and the distribution of the acetylated units ( P A: pattern of acetylation) has been demonstrated. Although there are numerous well-established methods for the determination of DP and F A values, this is not the case for P A . The methods available are either not straightforward or not sensitive enough, limiting their use for routine analysis. In this study, we demonstrate that by applying HOmodecoupled Band-Selective (HOBS) decoupling NMR on signals assigned by multidimensional Pure Shift NMR methods, P A can be easily and accurately determined on various chitosan samples. This novel methodology—easily implemented for routine analysis—could become a standard for chitosan P A assessment. In addition, by applying Spectral Aliased Pure Shift HSQC, the analysis was enhanced with the determination of triads. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, A simple approach to produce tailor-made chitosans with specific degrees of acetylation and molecular weights(MDPI AG, 2021-08-01)Chitin is a structural polysaccharide that is found in crustaceans, insects, fungi and some yeasts. Chitin deacetylation produces chitosan, a well-studied biopolymer with reported chemical and biological properties for diverse potential applications for drug delivery, metal ion absorption, scaffolds and tissue engineering. Most known properties of chitosan have been determined from samples obtained from a variety of sources and in different conditions, this is, from chitosans with a wide range of degrees of N-acetylation (DA) and molecular weight (MW). However, as for any copolymer, the physicochemical and mechanical characteristics of chitosan highly depend on their monomer composition (DA) and chain size (MW). This work presents a simple methodology to produce chitosans with specific and predictive DA and MW. Reaction with acetic anhydride proved to be an efficient method to control the acetylation of chitosan, DAs between 10.6% and 50.6% were reproducibly obtained. In addition to this, MWs of chitosan chains were reduced in a controlled manner in two ways, by ultrasound and by acidic hydrolysis at different temperatures, samples with MWs between 130 kDa and 1300 kDa were obtained. DAs were determined by 1H-NMR and MWs by gel permeation chromatography. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Alkali-treated Agave americana fiber for reinforcement of fly ash-based geopolymers(Taylor and Francis Ltd., 2022-01-01)The mechanical properties of Agave americana fibers treated with NaOH solutions (1, 5, and 20 wt.%) for different times (0.5, 1 and 3 h) were investigated. At these conditions, tensile strength and ultimate strain of the fibers were determined. The treatment that required the minimum resources to improve the mechanical performance was 1% NaOH for 1 h. Fiber surface after the alkaline treatment was analyzed by scanning electron microscopy (SEM); it showed partial remotion of impurities at the mildest condition (1% NaOH for 0.5 h) and an apparent surface decomposition when using the most harsh condition (20% NaOH for 3 h). Fly ash-based geopolymer composites with different treated fiber contents were prepared. The compressive, flexural, and splitting tensile strengths of the composite geopolymers at seven days of age were determined. Results indicated that the addition of fibers slightly influenced the compressive strength; however, the ductility capacity was improved by up to 26% when 1% of treated fiber was incorporated. Regarding the tensile behavior, results indicate a direct relationship of strength with the amount of fibers, up to 36% improvement with 1% fiber content. Morphological of the fiber-reinforced geopolymer matrices was finally studied by SEM. - 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, Ultrasound-assisted anthocyanins extraction from purple cabbage for optical biosensor of wound healing monitoring(Trans Tech Publications, 2024-03-29)The ethanol-water based extraction of phenolic bioactive components, anthocyanins, from purple cabbage (PC) was carried out. Ultrasound assisted extraction was performed and each cycle was set to 3 minutes. UV-visible absorbance was evaluated at each cycle (total 3 cycles) and the intensity of absorbance at 546~550 nm was interpreted as the extraction efficiency of anthocyanin. The pH sensibility of PC extracts was evaluated at pH 4, 5, 6, 7, and 8 and measured with UV-Visible spectrometry. Each pH condition, the extracts presented different color shades and wavenumbers of maximum absorbance proving their pH sensibility. Antioxidant activity of PC extract was evaluated and the excellent inhibition capacity was observed (~98%). PC extract was then embedded in alginate membrane to use as wound dressing materials. Alginate membrane with PC extract also presented high pH sensibility showing remarkable color changes after exposure to different pH environments.