ABSTRACT Purpose: Myopia, or nearsightedness, is one of the most common eye conditions worldwide. However, a comparison of the effectiveness of different laser-assisted interventions is lacking. Thus, we aimed to compare the efficacy and safety of LASIK and IntraLASIK in addressing myopia. Methods: The study was conducted in two ophthalmology clinics in Beijing, China, in 2022. A total of 84 patients (152 eyes) with different degrees of myopia were examined and underwent LASIK (n=46, 80 eyes) or IntraLASIK (n=38, 72 eyes). Keratometry, corneal topography, pachymetry, visual acuity evaluation, and corneal biomechanical analysis were performed before and after the intervention. Results: IntraLASIK produced more precise flaps than LASIK, with deviations of <8 mm and 0.1 mm from the intended thickness and diameter, respectively. LASIK resulted in nonuniform flaps, with thickness deviations of 5-86 mm. IntraLASIK demonstrated a superior efficacy for patients with severe myopia and thin corneas, with a mean spherical equivalent of 0.9 D at 6 months compared to the 1.4 D for LASIK. Approximately 91% and 83% of the patients with mild to moderate and severe myopia, respectively, achieved results within ± 0.49 D from the refractive target with IntraLASIK. Conclusions: Corneal hysteresis and corneal resistance factor decreased with an increase in laser intensity, and they decreased faster with thinner corneas. Thus, IntraLASIK is more useful than LASIK in patients with thin corneas and severe myopia. Purpose Myopia nearsightedness worldwide However laserassisted assisted lacking Thus Methods Beijing China 2022 8 152 (15 eyes n=46, n46 n 46 (n=46 n=38, n38 38 (n=38 7 eyes. . Keratometry topography pachymetry evaluation intervention Results < 01 0 1 0. diameter respectively 586 5 86 5-8 09 9 14 4 1. 91 83 049 49 0.4 Conclusions intensity 202 15 (1 n=46 n4 (n=4 n=38 n3 3 (n=3 58 5- 04 20 ( n=4 (n= n=3 2 n= (n

Abstract In housing, concrete masonry is one of the most used construction systems in Costa Rica. Under this construction system, beams and columns of equal width (12 or 15 cm) are usually required. In these cases, constructively, bending the reinforcing steel of the beam or column is used. This type of bend used “strangles” the reinforcement right in the section of maximum moment. Thus, it is relevant to experimentally investigate the behavior of these joints that are typically observed in constructions. The behavior of joints with two different reinforcement details and with 12 cm thick elements for use in housing was analyzed. Four joints were built, two with a “bottleneck” reinforcement detail (Type A Joint) and two with a 1:6 slope detail (Type B Joint). These were failed in the LanammeUCR Structures Laboratory under the application of a pseudo-dynamic cyclic load. Rotations were calculated and the hysteresis curve and elastoplastic curve were constructed for each joint. The behavior of the two types of joints was compared, as well as the experimental capacity results with respect to the expected theoretical capacity. The results obtained show that Type A Joints do not reach the calculated theoretical capacity and present a less ductile behavior than Type B Joints. It was concluded that it is preferable and advisable to use beam-column joints with the slope detail 1:6 as part of the earthquake-resistant system of a home.

Resumen En vivienda, la mampostería de concreto es uno de los sistemas constructivos más utilizados en Costa Rica. Bajo este sistema constructivo, se suelen requerir vigas y columnas de igual ancho (12 o 15 cm). En estos casos, constructivamente se recurre a doblar el acero de refuerzo de la viga o de la columna. Este tipo de doblez utilizado “estrangula” al refuerzo justo en la sección del máximo momento. De tal forma, resulta relevante investigar experimentalmente el comportamiento de estas uniones que típicamente se observan en las construcciones. Se analizó el comportamiento de uniones con dos distintos detalles de armado y con elementos de 12 cm de espesor para uso en vivienda. Se construyeron cuatro uniones, dos con un detalle de armado de “cuello de botella” (Unión Tipo A) y dos con detalle de pendiente 1:6 (Unión Tipo B). Estas se fallaron en el Laboratorio de Estructuras del LanammeUCR bajo la aplicación de una carga cíclica pseudo dinámica. Se calcularon rotaciones y se construyeron la curva de histéresis y la curva elastoplástica para cada unión. Se comparó el comportamiento de los dos tipos de uniones, así como, los resultados de capacidad experimentales con respecto a la capacidad teórica esperada. Los resultados obtenidos muestran que las Uniones Tipo A no alcanzan la capacidad teórica calculada y presentan un comportamiento menos dúctil que las Uniones Tipo B. Se logró concluir que es preferible y recomendable utilizar uniones viga-columna con el detalle de la pendiente 1:6 como parte del sistema sismorresistente de una vivienda.

This work aims to synthesize the alloy Co64Nb30B6 through mechanical alloying using a planetary ball mill. A disc rotation per minute and a ball/powder weight ratio of 300 rpm and 10:1 were used, with a milled time of 10 h, respectively. The characterization of the Co64Nb30B6 alloy was performed by X-ray diffraction (XRD), examined by scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS), thermoanalytical techniques (TGA/DTA), vibrating sample magnetometer (VSM) and confirmed by Braunauer, Emmet e Teller (BET) method type IV isotherms with a hysteresis loop for mesoporous materials. The results indicated that the evolution of the amorphous phase in the Co64Nb30B6 composition through the mechanical alloying process exhibited good soft magnetic properties with the addition of the metalloid element B and its excellent unique ferromagnetic properties. Through thermoanalytical analysis (TGA/DTA), it was shown that at higher temperatures, Co and Nb ions are oxidized by the environment and, therefore, the mass can be slightly increased to 14.9% and a probable contribution of boron in evolution stability thermal and magnetic in the amorphous phase, respectively. This suggests that the newly developed high-performance amorphous alloy Co64Nb30B6 has great application potential. CoNbB Co64Nb30B mill ballpowder powder 30 101 1 10: used h respectively Xray X ray XRD, XRD , (XRD) microscopeenergy microscope energy SEMEDS, SEMEDS SEM EDS (SEM-EDS) TGA/DTA, TGADTA TGA/DTA TGA DTA (TGA/DTA) VSM (VSM Braunauer BET (BET materials temperatures therefore 149 14 9 14.9 highperformance high performance potential 3 (XRD (SEM-EDS (TGA/DTA 14.

Abstract: Youth unemployment is one of the keys in youth studies. One of the premises that is usually considered given (unquestioned and unquestionable) is that young people suffer from unemployment to a greater extent than adults. However, we can ask ourselves, has it always been the same? Does it affect some birth cohorts more than others? Does it vary in different historical periods? Even going further, if for different cohorts the effects on youth unemployment as a result of their structural positions (intra-cohort) are invariant over time. This article aims to answer these questions using a long series in time (1985-2019) of Continuous Household Surveys in Uruguay, using the Age-Cohort-Period Detrended (ACPD) technique. The tool allows distinguishing the effects of these three variables (age, cohort, period) that are a linear combination. The results obtained open up new discussions and question the use that is usually made of "young people"; as if age itself equaled them, and above all if throughout history being young had the same consequences, in this case addressing unemployment.

Resumen: El desempleo juvenil constituye una de las claves en los estudios de jóvenes. Una de las premisas que habitualmente se considera dada (incuestionada e incuestionable) es que los jóvenes sufren el desempleo en mayor medida que los adultos. Sin embargo, podemos preguntarnos: ¿Siempre ha sido igual? ¿Afecta más a algunas cohortes de nacidos que a otras? ¿Varía en distintos períodos históricos? Incluso podemos ir más allá y preguntarnos si para distintas cohortes los efectos sobre el desempleo de los jóvenes producto de sus posiciones estructurales (intracohorte) son invariantes en el tiempo. Este artículo se aboca a responder estas interrogantes utilizando una serie larga (1985-2019) de la Encuesta Continua de Hogares en Uruguay, mediante la técnica age-cohort-period detrended (ACPD). La herramienta permite distinguir los efectos de estas tres variables (edad, cohorte y período), que son una combinación lineal. Los resultados obtenidos abren nuevas discusiones y cuestionan el uso que habitualmente se realiza de “los jóvenes”, como si la edad por sí misma los igualara y, sobre todo, como si a lo largo de la historia ser joven tuviera las mismas consecuencias, en este caso, abordando el desempleo.

Resumo: O desemprego juvenil é uma das chaves nos estudos da juventude. Uma das premissas que costuma ser considerada dada (inquestionável e inquestionável) é que os jovens sofrem mais com o desemprego do que os adultos. No entanto, podemos nos perguntar, sempre foi assim? Afeta algumas coortes de nascimento mais do que outras? Varia em diferentes períodos históricos? Indo ainda mais longe, questionando-nos se para diferentes coortes os efeitos sobre o desemprego juvenil resultantes das suas posições estruturais (intra-coorte) são invariantes ao longo do tempo. Este artigo tem como objetivo responder a essas perguntas por meio de uma longa série no tempo (1985-2019) de Pesquisas Domiciliares Contínuas no Uruguai, usando a técnica Age-Cohort-Period Detrended (ACPD). A ferramenta permite distinguir os efeitos dessas três variáveis (idade, coorte, período) que são uma combinação linear. Os resultados obtidos abrem novas discussões e questionam o uso que se costuma fazer de "jovens"; como se a própria idade os igualasse, e sobretudo se ao longo da história ser jovem teve as mesmas consequências, neste caso abordando o desemprego.

Abstract The residual tropical soils and their unsaturated condition add more complexity to the study of slope stability, introducing the suction variable to the stress state analysis. Due to the complexity of the pedological processes involved in their formation, tropical soils present variability in their parameters. This results in uncertainties regarding its behaviour in geotechnical structures. The most common promotion agent for deformation and loss of strength in residual soils in an unsaturated condition is the advancing of the wetting front due to rainfalls. A tropical climate with high levels of rainfall makes landslides a constant and dangerous phenomenon, leading to loss of human life and material. Thus, it is essential to verify the influence of precipitation on slope behaviour in residual conditions. This study analyzes the behaviour of a slope formed by a residual soil by determining the soil properties followed by a numerical analysis. Laboratory tests were performed to characterize the soil and determine the strength, hydraulic, and unsaturated condition parameters. In the numerical analysis, it was intended to visualize the influence of rainfall and hydraulic parameters on the pore pressure distribution inside the slope and in its stability. After the numerical step, it was found that the different rainfall characteristics (intensity and duration) increased the pore pressures and decreased the strength of the material. However, it was insufficient to trigger any failure mechanisms. The hydraulic parameters’ critical roles at seepage through the soil and how this is reflected in the calculations of safety factors were verified. stability analysis formation structures rainfalls phenomenon material Thus conditions step intensity duration However mechanisms verified

This experimental research evaluates the structural performance of laced reinforced concrete beams (LRC-45) in comparison to conventional reinforced concrete beams (RC-90) under reverse cyclic loading. Visual inspection revealed that LRC-45 exhibited superior crack resistance, even at high displacements, unlike RC-90, which displayed vertical cleavages and diagonal tension cracks. RC-90 demonstrated minimal ductility, initiating cracking at lower loads. Hysteresis response curves showed LRC-45 outperforming RC-90 in terms of cracking load and maximum load, with higher displacement capacity. The ductility factor of LRC-45 was 56.39% higher. Notably, LRC-45 exhibited a substantial 143.43% increase in cumulative energy dissipation, highlighting its superior energy-absorbing capacity. Additionally, stiffness analysis indicated significantly higher stiffness in LRC-45. The numerical analysis supported experimental findings, emphasizing the potential of laced reinforcement in enhancing structural resilience, energy dissipation, and stiffness. The novelty lies in the remarkable improvements offered by LRC-45, particularly its enhanced energy-absorbing capacity and stiffness, which are crucial for structures subjected to dynamic loads, such as seismic events. LRC45 LRC 45 (LRC-45 RC90 RC 90 (RC-90 loading LRC-4 resistance displacements RC90, 90, cracks RC-9 loads 5639 56 39 56.39 Notably 14343 143 43 143.43 dissipation energyabsorbing absorbing Additionally LRC45. 45. findings resilience LRC45, 45, events LRC4 4 (LRC-4 RC9 9 (RC-9 LRC- RC- 563 5 3 56.3 1434 14 143.4 (LRC- (RC- 56. 1 143. (LRC (RC

Abstract Surface runoff in agricultural areas promotes the transport of biological structures, such as arbuscular mycorrhizal fungi (AMF) spores, along with mineral particles, nutrients, and organic matter. Limited information exists regarding the relationships between the erosive process and the loss of AMF spores at the hillslope scale, as well as the effect of terracing on these relationships. The objective of this study was to quantify the loss of AMF spores in surface runoff water from agricultural soil managed under no-till and terraced conditions. The research was conducted in the Ribeirão Vermelho watershed, in a hillslope area in Cambé, Paraná, Brazil. Two experimental plots measuring 2.5 hectares each were installed, with one managed without terraces (NTP) and the other with level terraces (TP). At the lower end of the plots, a runoff flow measurement structure (H-channel) was installed to determine the flow rate and suspended spore count. The runoff duration, peak flow rate, and spore count were determined during the period from October 2019 to October 2022. The terrace reduced over 35% of suspended spore loss, and the hysteresis pattern showed a counterclockwise loop in NTP and a clockwise loop in TP for events with higher peak flow rates. The hysteresis pattern indicated rapid spore mobilization and transport in TP, suggesting that spores originated from more distant sources or required more energy for transportation in NTP. Overall, there is evidence that the terrace influences spore variability on the hillslope, reinforcing the need for terracing in agricultural hillslope areas. structures (AMF particles nutrients matter scale notill no till conditions watershed Cambé Paraná Brazil 25 2 5 2. (NTP TP. . (TP) Hchannel H channel (H-channel duration 201 2022 35 rates Overall (TP 20 202 3

ABSTRACT The magnetic torquer rod, also called a magnetorquer, is the most popular actuator for attitude control of satellites in low Earth orbit. In the case of nano and picosatellites, the available inner space is quite limited, as is the maximum power value. An optimal design solution is highly desirable to produce adequate torque while minimizing energy consumption and mass. Based on the axiomatic design theory, a solution was developed by establishing the requirements – wire diameter, magnetic dipole moment, voltage, and solenoid length – and the physical domain variables – number of turns, current, resistance, and wire length. As a result of the modelling, the design system is decoupled. The choice of core material can also contribute to the actuator’s improvement. Two options are proposed in this work: the FINEMET, a nanocrystal composed of various metals and other elements, and the FeNi50 alloy, for comparative performance. In terms of design parameters, four prototypes were developed to evaluate different wiring configurations and two core materials. The test results of the design options reveal a contrasting performance concerning core material: while the utilization of nanocrystalline material yields superior hysteresis characteristics or linearity behavior, the FeNi50 alloy exhibits enhanced magnetization magnitude. rod magnetorquer orbit picosatellites limited value mass theory diameter moment voltage turns current resistance modelling decoupled actuators s improvement work FINEMET elements FeNi FeNi5 parameters materials behavior magnitude

Abstract The effect of mechanical stress on hysteresis losses of electrical steel sheets is investigated in this paper. Experimental data obtained from a dedicated bench are used in a curve fitting procedure to analyze the parameters behavior for a hysteresis losses model over a range of mechanical compressive and tensile stresses. By applying the concept of equivalent stress, a finite element model is simulated, and the hysteresis losses are a posteriori calculated considering an equivalent stress distribution over a single-phase induction motor stator. paper stresses simulated singlephase single phase stator

As nanopartículas (NPs) à base de óxido de ferro, como magnetita e maguemita, têm grande destaque em diversas áreas da ciência, inclusive na medicina. Há décadas, elas são usadas na reposição de ferro para pacientes com anemia, como agentes de contraste em ressonância magnética (MRI – “Magnetic Resonance Imaging”), na entrega de agentes terapêuticos mediada ou não por gradiente de campo magnético, em terapias térmicas foto e magnetoestimuladas, entre outras. Neste artigo, apresentamos suas propriedades magnéticas. Discutimos de forma breve seu ordenamento ferrimagnético, a importância da anisotropia magnética e sua relação com a histerese magnética (modelo de Stoner-Wohlfarth) e o regime superparamagnético. As diferenças entre superparamagnetismo e paramagnetismo são enfatizadas, além da importância da estabilidade coloidal dessas nanoestruturas para aplicações biomédicas. Finalmente, diversas aplicações biomédicas são discutidas, entre elas hipertermia magnética, terapia fototérmica, imunoterapia e uma nova técnica de imagem com potencial clínico, conhecida como “Magnetic Particle Imaging” (MPI). NPs (NPs maguemita ciência medicina décadas anemia MRI Magnetic Imaging, Imaging , Imaging”) magnético magnetoestimuladas outras artigo magnéticas ferrimagnético modelo StonerWohlfarth Stoner Wohlfarth Stoner-Wohlfarth superparamagnético enfatizadas Finalmente discutidas fototérmica clínico MPI. MPI . (MPI) (MPI

Iron oxide-based nanoparticles (NPs), such as magnetite and maghemite, are highly prominent in various scientific fields, including medicine. For decades, they have been used for iron supplementation in patients with anemia, as contrast agents in magnetic resonance imaging (MRI), in the delivery of therapeutic agents mediated or not by magnetic field gradients, and in photo- and magneto-stimulated thermal therapies, among other applications. In this article, we present their magnetic properties. We briefly discuss their ferrimagnetic ordering, the importance of magnetic anisotropy and its relation to magnetic hysteresis (Stoner-Wohlfarth model), and the superparamagnetic regime. The differences between superparamagnetism and paramagnetism are emphasized, as well as the importance of the colloidal stability of these nanostructures for biomedical applications. Finally, various biomedical applications are discussed, including magnetic hyperthermia, photothermal therapy, immunotherapy, and a new imaging technique with clinical potential known as Magnetic Particle Imaging (MPI). oxidebased oxide based NPs, NPs , (NPs) maghemite fields medicine decades anemia MRI, MRI (MRI) gradients photo magnetostimulated magneto stimulated therapies article properties ordering StonerWohlfarth Stoner Wohlfarth model, model model) regime emphasized Finally discussed hyperthermia therapy immunotherapy MPI. MPI . (MPI) (NPs (MRI (MPI

Abstract The lack of data is a hindrance to the experimental determination of magnetic cores characteristics. This work presents a non-invasive and field-applicable methodology for electromagnetic devices characterization. Based on fundamental equations of electromagnetism and routine tests, the methodology was applied to obtain, at low frequency: the core loss separation, the hysteresis loop and its BH curve of a three-phase dry core-type transformer. The required equipment and the procedures to do the characterization are presented and discussed. The results were compared with experimental data obtained from tests that were carried out on the same material using a Single Sheet Tester device. The results show a difference in losses of 4.9% for hysteresis, 1.5% for dynamic, and 3.3% for total losses. In the no-load test comparison there was a difference of 4% for dynamics and 1.8% in total losses. The proposed methodology can be applied to different magnetic core types as well as to single-phase transformers and reactors. characteristics noninvasive non invasive fieldapplicable field applicable obtain frequency separation threephase three phase coretype type transformer discussed device 49 4 9 4.9 15 1 5 1.5 dynamic 33 3 3.3 noload no load 18 8 1.8 singlephase single reactors 4. 1. 3.

Abstract Wetting of metal droplet on the solid substrate is a fundamental phenomenon which is applicable to the surface chemistry. When an oscillation field is included in the wetting condition, the wetting process shows significant advancing and receding behaviors. Also, the use of ultrasonic oscillation field is promising in welding. However, some odd morphologies led by the ultrasonic-treatment have shown wetting kinetics which have not been fully investigated. The high frequency ultrasonic vibration brings hysteresis to the contact angle, whose extra energy is attributed by the oscillation field. The ultrasonic wetting process is excited by the 20 kHz frequency periodic oscillation, during which droplet is swaying cyclically. However, after capturing the transformation of droplet morphologies, it is found that the frequency of each swaying cycle is identified to be 180 ms. Theoretical investigations have also quantitively proved that the energy for the contact angle decrease origins from the ultrasonic field, and the wettability is in a great enhancement. Thermal and kinetic effects of ultrasonic are investigated by making theoretical calculations, the 20 kHz ultrasonic field lasting for 5 seconds. Thermodynamics, vibrational mechanics, and interfacial phenomena affect the sonochemistry of wetting.

An experimental apparatus for obtaining magnetic hysteresis curves was built, with the participation of undergraduate physics students, aiming at a visualization of the fundamentals that characterize the magnetic response of ferromagnetic materials subjected to alternating magnetic fields. Hysteresis loops of the secondary core of a transformer were obtained, visualizing them on the screen of an oscilloscope in the graphic form of voltage in a capacitor connected to the secondary winding as a function of the voltage measured in a resistor connected to the primary. Loops were obtained for five values of voltage applied to the primary of the transformer in the range of 160–220 V. An increase in coercive, remanent and maximum magnetization fields was observed with increasing primary voltage. The relative magnetic permeability curves show a maximum close to the coercive field values, and thus the non-linearity of the permeability with the magnetic field intensity was observed. Finally, with increasing voltage, the students estimated the power lost in 5 hysteresis curves associated with the rotation of magnetic dipoles and dynamic factors. built 160220 160 220 160–22 V nonlinearity non linearity Finally factors 16022 16 22 160–2 1602 1 2 160–

Um aparato experimental para a obtenção de curvas de histerese magnética foi construído, com a participação de estudantes de licenciatura em física, visando uma visualização dos fundamentos que caracterizam a resposta magnética de materiais ferromagnéticos submetidos a campos magnéticos alternados. Foram obtidos laços de histereses do núcleo secundário de um transformador, visualizando-os na tela de um osciloscópio na forma gráfica de tensão em um capacitor conectado ao enrolamento secundário em função da tensão medida em um resistor conectado ao enrolamento primário. Os laços foram obtidos para cinco valores de tensão aplicadas ao primário do transformador na faixa de 160–220 V. Foi observado um aumento nos campos coercivo, remanente e magnetização máxima com o aumento da tensão no primário. As curvas de permeabilidade magnética relativa apresentam um máximo próximo aos valores de campo coercivo, e assim observou-se a não linearidade da permeabilidade com o campo intensidade magnética. Por fim, com o aumento da tensão, os estudantes estimaram a potência perdida em 5 curvas de histerese associadas a rotação de dipolos magnéticos e fatores dinâmicos. construído física alternados visualizandoos visualizando 160220 160 220 160–22 V coercivo observouse observou se fim dinâmicos 16022 16 22 160–2 1602 1 2 160–

ABSTRACT. Knowledge of the relationship between the equilibrium moisture content of the product and the air that involves it is essential to guarantee product quality and preserve its characteristics during storage. This trend can be studied by sorption isotherms. Thus, this study aimed to obtain desorption and adsorption isotherms of soybean grains to determine the mathematical model that best fits the experimental data and analyze the hysteresis phenomenon. Soybean grains with a moisture content of 21.95% (db) were used to verify the desorption process. The grains were dried until 3.50% (db) for the adsorption process. The static-gravimetric method was employed to determine the equilibrium moisture content of the grain at different temperatures (10, 20, 30, 40, and 50°C) and relative humidity levels (0.10 to 0.92%). Eight mathematical models were fitted to the experimental data. The modified Halsey model satisfactorily represented the desorption and adsorption phenomena of soybean grains. The equilibrium moisture content of soybean grains increased along with an increment in water activity. The increase in temperature led to a reduction in the equilibrium moisture content of soybean grains at a constant water activity. The equilibrium moisture content values obtained by desorption are higher than those obtained by adsorption, indicating the hysteresis phenomenon at the studied temperature range. The isotherms obtained for the desorption and adsorption process were classified as type III because of the high oil content in soybean grains.

Resumo A utilização de cimento pré-hidratado na formulação de argamassas e concretos é comum, pois nem sempre há um controle efetivo na produção do cimento, moagem, transporte e posterior armazenamento. Este trabalho apresenta um estudo de caso sobre a otimização de aditivo para uso com cimento pré-hidratado, avaliando as mudanças nas propriedades reológicas do cimento Portland pré-hidratado artificialmente. O cimento foi pré-hidratado artificialmente por exposição à umidade relativa (URs) de 90%, em ambiente de solução saturada de NH4Cl. Adicionalmente, as pastas de cimento foram avaliadas com e sem superplastificante. O teste de fluxo escalonado usando uma geometria de placas paralelas foi o método escolhido para avaliar o comportamento reológico, viscosidade aparente, tensão de escoamento e área de histerese de cada pasta em idade precoce. A reometria oscilatória foi realizada para avaliar o módulo de armazenamento (G'), comparando a consolidação com a cinética de hidratação obtida pela avaliação calorimétrica das mesmas suspensões. Os resultados iniciais do reômetro indicam que a amostra pré-hidratada apresenta menor nível de tensão de cisalhamento do que a amostra de referência, devido à maior reatividade da amostra não pré-hidratada.

Abstract The use of pre-hydrated cement in formulation of mortar and concrete is common because there is not always effective control on the cement production, grinding, transportation and subsequent storage. This paper presents a case study on the optimization of admixture for use with prehydrated cement by assessing changes in the rheological properties of Portland cement artificially pre-hydrated. The cement was artificially pre-hydrated by exposure to relative humidity (RHs) of 90%, in an environment of NH4Cl saturated solution. Additionally, the cement pastes were evaluated with and without superplasticizer. Stepped flow test using a parallel-plate geometry was the method choose to evaluate the rheological behavior, apparent viscosity, yield stress and hysteresis area of each paste at the early age. Oscillatory rheometry was conducted to evaluate the storage modulus (G’), comparing the consolidation with the hydration kinetics obtained by calorimetric evaluation of the same suspensions. Initial rheometer results indicate that the pre-hydrated sample presents lower level of shear stress than the reference sample, because of the higher reactivity of the non-pre-hydrated sample.