Catálogo de publicaciones - revistas

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<jats:p xml:lang="en">The process of depleting the natural sources of virgin sand and aggregate makes it challenging to satisfy the demand for construction work. Therefore, in a context of sustainable construction, this study examined the feasibility of utilizing dredged sediments (DS) as a substitute for sand in non-structural controlled low-strength materials (CLSM). A total of two types of dredged sediments, coarser and finer, were collected from two different sources. Then, nine CLSM mixtures were prepared by using different proportions of natural sand (virgin sand) and dredged sediments. Each mixture was tested for flowability, unconfined compressive strength, density and excavatability. Flow consistency decreased with the amount of dredged sediments and presence of finer material in CLSM. Strength results were found within required specification for all nine CLSM tested in this study. Overall, flow consistency, strength and excavatability were found dependent on the characteristics of dredged sediments. This study showed that dredged sediments can be successfully used as a sand substitute for CLSM production.</jats:p>

<jats:p xml:lang="en">The process of depleting the natural sources of virgin sand and aggregate makes it challenging to satisfy the demand for construction work. Therefore, in a context of sustainable construction, this study examined the feasibility of utilizing dredged sediments (DS) as a substitute for sand in non-structural controlled low-strength materials (CLSM). A total of two types of dredged sediments, coarser and finer, were collected from two different sources. Then, nine CLSM mixtures were prepared by using different proportions of natural sand (virgin sand) and dredged sediments. Each mixture was tested for flowability, unconfined compressive strength, density and excavatability. Flow consistency decreased with the amount of dredged sediments and presence of finer material in CLSM. Strength results were found within required specification for all nine CLSM tested in this study. Overall, flow consistency, strength and excavatability were found dependent on the characteristics of dredged sediments. This study showed that up to 50% of substitution of sand with DS in CLSM improved strength and density. Furthermore, flow consistency was found to decrease with increase in the amount of DS in CLSM mixtures.</jats:p>

<jats:p xml:lang="en">The current study investigates the possibility of volcanic Tuff of Earth of Datça (ED) in Turkey to be used as an aluminosilicate source in producing a geopolymer foam for thermal insulation. An extensive evaluation of the effects of fine sand–to–pozzolan and Al powder–to–pozzolan ratios on the physical, mechanical, and thermal properties and morphology (porosity, average and maximum pore diameter, pore size distribution) of the pores were carried out. The sodium silicate and potassium hydroxide (12.5 M) solutions with an activator ratio of 2.5 were used as alkali activators, and Al powder was used as a foaming agent. Research results reveal that Earth of Datça is a suitable precursor for producing a geopolymer foam. Fine sand and aluminum powder contents are critical to the optimum foam structure. The addition of finely ground silica sand ensured the volumetric stability of the binder and prevented the collapse after swelling of the binder. The optimum Al powder–to–pozzolan ratio was determined as 0.5% because it gives higher physical, mechanical, and thermal properties due to the more homogenous microstructure with finer pore size and narrower pore size distribution lower degree of interconnectivity between the pores. Research results also show that the natural volcanic Tuff of Datça Peninsula as an aluminosilicate source gives promising results in the field of producing highly porous geopolymers with low thermal conductivity (0.087–0.134 W/mK), high porosity (72.3–82.6%) and an adequate compressive strength (0.40–2.09 MPa). This study contributes to the literature that Earth of Datça–based geopolymer foam may function well as an insulation material for building enclosures.</jats:p>

<jats:p xml:lang="en">The purpose of the current study is to investigate the possibility of volcanic Tuff of Earth of Datça (ED) in Turkey to be used as an aluminosilicate source in the production of a geopolymer foam for thermal insulation. An extensive evaluation of the effects of fine sand-to-pozzolan and Al powder-to-pozzolan ratios on the physical, mechanical, and thermal properties and morphology (porosity, average and maximum pore diameter, pore size distribution) of the pores were carried out. The sodium silicate and potassium hydroxide (12.5 M) solutions with an activator ratio of 2.5 were used as alkali activators and Al powder was used as a foaming agent. Research results reveal that Earth of Datça is a suitable precursor for the production of a geopolymer foam. Fine sand and aluminum powder contents are key factors on optimum foam structure. Addition of finely ground silica sand ensured the volumetric stability of the binder and prevented the collapse after swelling of the binder. The optimum Al powder-to-pozzolan ratio was determined as 0.5 % because it gives higher physical, mechanical and thermal properties due to the more homogenous microstructure with finer pore size, narrower pore size distribution and lower degree of interconnectivity between the pores. Research results also show that natural volcanic Tuff of Datça Peninsula as aluminosilicate source gives promising results in the field of producing highly porous geopolymers with low thermal conductivity (0.087-0.134 W/mK), high porosity (72.3-82.6 %) and an acceptable compressive strength (0.40-2.09 MPa). This study contributes to the literature that Earth of Datça-based geopolymer foam may function well as an insulation material for building enclosure.</jats:p>

<jats:p xml:lang="en">Recently, it has been known that carbon fiber, a conductive fiber, is used in different mixture designs and the development of electrically conductive cementitious materials. However, the evaluation of ferrochrome slag as a recycled aggregate in the mixture of these special concretes has still not been investigated. In this study, electrically conductive mortars were produced using 100% recycled ferrochrome slag aggregate with a particle size of less than 1 mm as filling material and using carbon fiber in 4 different ratios, 0%, 0.5%, 0.75%, and 1%. To investigate the electrical conductivity properties, the resistivity values of the samples were measured at five different times within 2–180 days. In addition, 28-day compressive strength, flexural strength, dynamic resonance, ultrasonic pulse velocity, Leeb hardness, scanning electron microscope, and X-Ray Diffraction tests were performed on all samples. The results were compared with the literature, proving that ferrochrome slag could be used as a reasonable aggregate in conductive mortars. The age effect was minimal in CF-added mixtures. With the addition of 1% CF, the resistivity values decreased approximately 40 times compared to the reference. Moreover, SEM analyses of the CF-0.75 sample showed that the CFs adhered to form a conductive network between the components in the ferrochrome-filled compact structure.</jats:p>

<jats:p xml:lang="en">Recently, it is known that carbon fiber, which is a conductive fiber, is used in different mixture designs and developing electrically conductive cementitious materials. However, the evaluation of ferrochrome as a recycled aggregate in the mixture of these special concretes has still not been investigated. In this study, electrically conductive mortars were produced by using 100% recycled ferrochrome aggregate with a particle size of less than 1 mm as filling material and using carbon fiber (CF) in 4 different ratios, 0%, 0.5%, 0.75% and 1%. 2, 14, 28, 90 and 180 days electrical resistivity properties of the obtained samples were investigated. In addition, 28-day compressive strength, flexural strength, dynamic resonance, ultrasonic pulse velocity (UPV), Leeb hardness, scanning electron microscope (SEM) and X-Ray Diffraction (XRD) tests were performed on all samples. The obtained results were compared with the literature and it was proved that ferrochrome can be used as a reasonable aggregate in conductive mortars.</jats:p>

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<jats:p xml:lang="en">An experimental work was herein presented focusing the effect of different type, shape and volume fraction of fibers on the hardened properties of concrete including compressive, splitting tensile and flexural strengths at 7 and 28 curing days. A control concrete mixture including no fiber was prepared and six fiber-reinforced concrete (FRC) mixtures were designed by using two different fiber types and volume fractions. Two types of steel fibers having different shapes (short straight and long hooked end) and polypropylene fiber were used with the volume fraction of 0.4% and 0.8%. The load-deflection curves and toughness of the specimens were analyzed based on ASTM C1609. The results showed that the utilization of short straight steel fibers with 0.8% volume fraction was most efficient at enhancing the compressive strength with 9.98% while the use of 0.8% long hooked end steel fibers provided better splitting tensile and flexural strengths with 33.33% and 30.35%, respectively, compared to specimen with no fiber at 28 curing day. Besides, the long hooked end steel fibers with the volume fraction of 0.8% contributed to an excellent deflection hardening behavior resulting in higher load deflection capacity and higher toughness values at peak load, L/600 and L/150. On the other hand, with incorporation of polypropylene fiber, all strength values decreased regardless of the volume fraction and curing days.</jats:p>

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