The incorporation of a recycled concrete aggregate (RCA) as a replacement of natural aggregates (NA) in road construction has been the subject of recent research. This tendency promotes sustainability, but its use depends mainly on the final product’s properties, such as chemical stability. This study evaluates the physical and chemical properties of RCAs from two different sources in comparison with the performance of NA. One RCA was obtained from the demolition of a building (recycled concrete aggregate of a building—RCAB) and another RCA from the rehabilitation of a Portland cement concrete pavement (recycled concrete aggregate from a pavement—RCAP). Characterization techniques such as X-ray fluorescence (XRF), X-ray diffraction (XRD), UV spectroscopy, and atomic absorption spectrometry were used to evaluate the RCAs’ coarse fractions for chemical potential effects on asphalt mixtures. NA was replaced with RCA at 15%, 30%, and 45% for each size of the coarse fractions (retained 19.0, 12.5, 9.5, and 4.75 sieves in mm). The mineralogical characterization results indicated the presence of quartz (SiO2) and calcite (CaCO3) as the most significant constituents of the aggregates. XFR showed that RCAs have lower levels of CaO and Al2O3 concerning NA. Potential reactions in asphalt mixtures by nitration, sulfonation, amination of organic compounds, and reactions by alkaline activation in the aggregates were discarded due to the minimum concentration of components such as NO2, (–SO3H), (–SO2Cl), and (Na) in the aggregates. Finally, this research concludes that studied RCAs might be used as replacements of coarse aggregate in asphalt mixtures since chemical properties do not affect the overall chemical stability of the asphalt mixture.
La ludoevaluación es una práctica evaluativa que busca valorar los desempeños de los estudiantes a través de experiencias lúdicas, que permitan obtener información oportuna y pertinente sobre sus aprendizajes y reducir los niveles de ansiedad, propios de las experiencias de evaluación tradicional. El objetivo del estudio fue comprender las dinámicas que se generan al realizar experiencias de evaluación, mediadas por la lúdica, en el contexto de una comunidad de aprendizaje docente universitaria. Se trató de una investigación con diseño descriptivo, en la que se desarrollaron experiencias de ludoevaluación con 160 estudiantes de una Universidad privada colombiana. Estas experiencias se llevaron a cabo en 5 fases: fundamentación teórica, diagnóstico, diseño, aplicación y reflexión. Los resultados evidencian un cambio en la percepción de los estudiantes frente a los procesos evaluativos, sobresaliendo emociones positivas, como: el entusiasmo, la alegría y la seguridad. Se concluye que es posible valorar los aprendizajes en escenarios menos estresantes a los que habitualmente se realizan, propios de la evaluación tradicional de corte normativo y cuantitativo.
Virtual microscopes are devices that employ an automated XYZ mechanism to scan a sample, leading to the obtention of a series of small pictures that, when merged, compose a high-quality representation of the specimen. Due to the assembly tolerances, these devices may suffer from zones out of focus, reducing the quality of the final image. To solve this problem, researchers employ evaluation methods to calculate the blurriness of the image, and when an out of focus picture is located, performs the process of autofocus. Because of the variation on the types of samples, especially in pathology, the existing evaluation methods may fail to deliver a proper blur detection. This article proposes an optimized algorithm for the detection of the blurriness while conducting the sample scan in real time, ensuring that every scanned picture will be in focus. For this purpose, the algorithm relies on two functions, the comparison of the overlapping zones of two consecutive images, and the multivariate linear regression of a series of focus functions. The algorithm proved to be a reliable tool when applied in different pathology samples.
This paper presents the experimental results given by the operation of a chemical sorption refrigeration system using Expanded Graphite/Activated Carbon/Lithium Chloride (AC/GE/LiCl)-Adsorbent (NH3 in solution with a 25% concentration). Experimental protocol with the characteristics of the experimental rig developed, working pair specifications and the procedure that has developed in the process is described in detail. Results are presented for different behaviors of the system, where the desorption stage is driven by forced convection. Measurements of the thermal variables of the system show that the adsorption-desorption cycles in the test accomplished, with high and low-pressure zones clearly defined. The cooling effects for the pair material studied have the expected behavior for the mixture proposed.
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