219 research outputs found

    Estudio de la velocidad de corrosión de aceros embebidos en morteros de cemento sustituidos con residuo de catalizador de craqueo catalítico (FC3R)

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    This paper reports on a study of the corrosion levels in steel bars embedded in mortars made with a blend of Portland cement and (0-20%) spent fluid catalytic cracking catalyst residue (FC3R), with a variable (0.3-0.7) water/binder (w/b) ratio. The specimens were stored in the following conditions: relative humidity of 40, 80 or 100% and CO2 concentrations of 5 and 100%. The steel corrosion rate was measured with polarization resistance techniques. In the absence of aggressive agents, the steel was found to remain duly passivated in mortars with an FC3R content of up to 15% under all the conditions of relative humidity tested. The reinforcement corrosion level in mortars with a w/b ratio of 0.3 and 15% FC3R subjected to accelerated carbonation was similar to the level observed in the unblended Portland cement control mortar.En este trabajo se ha estudiado el nivel de corrosión de barras de acero embebidas en morteros de cemento Portland con relación agua/material cementante (a/mc) variable (0,3-0,7), en los que parte del cemento (0-20%) se sustituyó por catalizador de craqueo usado (FC3R). Las condiciones de conservación de las probetas elaboradas fueron las siguientes: distintas humedades relativas (40, 80 y 100%) y dos concentraciones de CO2 (5 y 100%). La velocidad de corrosión de los aceros se midió mediante la técnica de resistencia de polarización. Se ha podido determinar que, bajo las distintas condiciones de humedad relativa y ausencia de agresivo, los aceros se mantuvieron correctamente pasivados en los morteros con contenidos de FC3R de hasta el 15%. El nivel de corrosión que presenta el refuerzo embebidos en morteros con sustitución de un 15% de cemento por FC3R y relación a/mc 0,3, al ser sometidos a un proceso de carbonatación acelerada, era muy similar al mostrado por el mortero patrón, sin FC3R

    Outstanding aspects on the use of spent FCC catalyst in binders

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    4 pages, 3 fiures, 7 tables.-- En: 1st Spanish National Conference on Advances in Materials Recycling and Eco – Energy Madrid, 12-13 November 2009.-- Editors: F. A. López, F. Puertas, F. J. Alguacil and A. Guerrero.FCC is a waste material from petrochemical plants which has interesting properties for preparing binders. FCC is lightly grey in color, and white FCC-portland cements with L*≥85 can be prepared. FCC reactivity is enhanced by grinding and it is attributed to pozzolanic reaction towards lime. Stratlingite is the main hydrated product from pozzolanic reaction, and CSH and CAH are also formed. Reactivity of FCC is high, and low curing temperature does not affect this contribution to strength in hardened mixtures. Additionally, high strength concrete can be easily prepared, and compressive strength greater 100MPa can be reached. Mixtures with low w/b ratio showed good behaviour in carbonation tests.Authors thank to Ministerio de Ciencia y Tecnología of Spain and FEDER the financial support of MAT 2001-2694 and BIA 2004-0052 projects.Peer reviewe

    The impact of age and comorbidity on the postoperative outcomes after emergency surgical management of complicated intra-abdominal infections

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    Age-adjusted Charlson Comorbidity Index (a-CCI) score has been used to weight comorbid conditions in predicting adverse outcomes. A retrospective cohort study on adult patients diagnosed with complicated intra-abdominal infections (cIAI) requiring emergency surgery was conducted in order to elucidate the role of age and comorbidity in this scenario. Two main outcomes were evaluated: 90-day severe postoperative complications (grade ≥ 3 of Dindo-Clavien Classification), and 90-day all-cause mortality. 358 patients were analyzed. a-CCI score for each patient was calculated and then divided in two comorbid categories whether they were ≤ or > to percentile 75 (= 4): Grade-A (0–4) and Grade-B (≥ 5). Univariate and multivariate regression analyses were performed, and the predictive validity of the models was evaluated by the area under the receiver operating characteristics (AUROC) curve. Independent predictors of 90-day severe postoperative complications were Charlson Grade-B (Odds Ratio [OR] = 3.49, 95% confidence interval [95%CI]: 1.86–6.52; p < 0.0001), healthcare-related infections (OR = 7.84, 95%CI: 3.99–15.39; p < 0.0001), diffuse peritonitis (OR = 2.64, 95%CI: 1.45–4.80; p < 0.01), and delay of surgery > 24 hours (OR = 2.28, 95%CI: 1.18–4.68; p < 0.02). The AUROC was 0.815 (95%CI: 0.758–0.872). Independent predictors of 90-day mortality were Charlson Grade-B (OR = 8.30, 95%CI: 3.58–19.21; p < 0.0001), healthcare-related infections (OR = 6.38, 95%CI: 2.72–14.95; p < 0.0001), sepsis status (OR = 3.98, 95%CI: 1.04–15.21; p < 0.04) and diffuse peritonitis (OR = 3.06, 95%CI: 1.29–7.27; p < 0.01). The AUROC for mortality was 0.887 (95%CI: 0.83–0.93). Post-hoc sensitivity analyses confirmed that the degree of comorbidity, estimated by using an age-adjusted score, has a critical impact on the postoperative course following emergency surgery for cIAI. Early assessment and management of patient’s comorbidity is mandatory at emergency setting

    Unveiling the Dependence between Hydroxyl Radical Generation and Performance of Fenton Systems with Complexed Iron

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    [EN] Humiclike substances (HLS) have been demonstrated to be useful auxiliaries to drive the (photo)-Fenton process at mild pH, by avoiding iron inactivation via formation of active complexes. However, the actual performance of the process is affected by a manifold of opposite processes. In this work, the generation of hydroxyl radical-like reactive species in the Fentonlike process has been investigated using electron paramagnetic resonance, employing 5,5-dimethyl-1-pyrroline-N-oxide as a probe molecule. The signal obtained with the Fe(II)-HLS-H2O2 system at pH = was very intense but decreased with time, in line with the difficult reduction of the formed Fe(III) to Fe(II). On the contrary, the signal of the Fe(III)-HLS-H2O2 system was weak but stable. The most intense signal was observed at HLS concentration of ca. 30 mg/L. Interestingly, the performance of the Fenton system at pH = 5 to degrade caffeine followed the same trends, although caffeine removal was very low after 1 h of irradiation. The results were more evident in a solar simulated photo-Fenton process, where an increase in the abatement of caffeine was observed until an HLS concentration of 30 mg/L, where 98% removal was reached after 1 h.The authors want to acknowledge the financial support from Ministerio de Ciencia, Innovacion y Universidades (RTI2018-097997-B-C31) and European Union (645551-RISE-2014, MAT4TREAT). P.G.-N. would like to thank Spanish Ministerio de Economia y Competitividad for her fellowship (BES-2016-077962).García-Negueroles, P.; García-Ballesteros, S.; Amat Payá, AM.; Laurenti, E.; Arqués Sanz, A.; Santos-Juanes Jordá, L. (2019). Unveiling the Dependence between Hydroxyl Radical Generation and Performance of Fenton Systems with Complexed Iron. ACS Omega. 4(26):21698-21703. https://doi.org/10.1021/acsomega.9b02241S216982170342

    Pentachlorophenol Removal from Water by Soybean Peroxidase and Iron(II) Salts Concerted Action

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    [EN] Soybean peroxidase (SBP) has been employed for the treatment of aqueous solutions containing pentachlorophenol (PCP) in the presence of hydrogen peroxide at pH range 5-7. Reaction carried out with 1mg/L of PCP, 4mg/L of H2O2, and 1.3x10(-9)M of SBP showed a fast initial elimination of PCP (ca. 30% in 20min), but the reaction does not go beyond the removal of 50% of the initial concentration of PCP. Modification in SBP and PCP amounts did not change the reaction profile and higher amounts of H2O2 were detrimental for the reaction. Addition of Fe(II) to the system resulted in an acceleration of the process to reach nearly complete PCP removal at pH 5 or 6; this is more probably due to a synergetic effect of the enzymatic process and Fenton reaction. However, experiments developed in tap water resulted in a lower PCP elimination, but this inconvenience can be partly overcome by leaving the tap water overnight in an open vessel before reaction.We want to acknowledge Davide Mainero from Acea Pinerolese for his collaboration in this research. The authors want to thank the financial support of the European Union (PIRSES-GA-2010-269128, EnvironBOS and Marie Sklodowska-Curie Research and Innovation Staff Exchange projectH2020-MSCA-RISE-2014, Mat4treaT-project number: 645551) and Spanish Ministerio de Educacion y Ciencia (CTQ2015-69832-C4-4-R). Sara Garcia-Ballesteros would like to thank the Spanish Ministerio de Economia y Competitividad for her fellowship (BES-2013-066201).Tolardo, V.; García-Ballesteros, S.; Santos-Juanes Jordá, L.; Vercher Pérez, RF.; Amat Payá, AM.; Arqués Sanz, A.; Laurenti, E. (2019). Pentachlorophenol Removal from Water by Soybean Peroxidase and Iron(II) Salts Concerted Action. 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    Method of analysis to evaluate the CFRP ShearStrengthened in Reinforced Concrete

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    [ES] En este trabajo de investigación se comparan diferentes modelos de cálculo de refuerzo a esfuerzo cortante mediante polímeros reforzados con fibras de carbono (CFRP) clasificados según el modo de fallo. En el diseño del refuerzo se tiene en cuenta la modificación del comportamiento de la viga por el refuerzo. Los estudios muestran que siempre que sea posible, la dirección principal de las fibras debe ser perpendicular a las fisuras de cortante. La contribución del refuerzo a la resistencia a cortante de la viga depende de los estribos de acero existentes en la viga original. Cuando aumenta el espesor del refuerzo la resistencia a cortante de la viga se incrementa. Esta relación tiende a ser lineal cuando la viga no está fisurada. Por último indicar que tanto el ángulo de inclinación de las fisuras, como el cortante resistido por el refuerzo, dependen del ángulo de inclinación de las fibras.[EN] Different models of shear-strengthened calculation by means of Carbon Fiber-Reinforced Polymer (CFRP) are compared in this investigation works classified according to the way of failure. We take into account the modification of the behavior of the beam for the reinforcement in its design. The surveys show that as long as it is possible the main direction of the fibers must be perpendicular to the shear crakc. The contribution of the reinforcement to the resistance to shear-strengthened of the beam depends on the steel stirrups in the original beam. When the reinforcement strips thickness increases the resistance to shear-strengthened of the beam also increases. This relation tends to be lineal when the beam is not cracks. At last we must state that both the inclination angle of the crack and the shear-strengthened resisted by the reinforcement depend on the inclination angle of the fiber.Parra, C.; Martínez-Conesa, E.; Valcuende Payá, MO.; Garrido, A. (2012). Análisis de métodos para evaluar el refuerzo a esfuerzo cortante con CFRP en vigas de hormigón armado. Informes de la Construcción. 64(526):197-206. doi:10.3989/ic.11.007S1972066452
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