A comparative study of recycled aggregates from concrete and mixed debris as material for unbound road sub-base

Siete áridos reciclados de residuos de construcción y demolición (RCD) se han evaluado como zahorras para la construcción de sub-bases de carreteras. Los resultados muestran que los áridos reciclados de hormigón cumplen todas las especificaciones del Pliego de Prescripciones Técnicas Generales para Obras de Carreteras de España (PG-3) para su uso en capas estructurales (sub-base) de las categorías de tráfico T3 y T4. Algunos áridos reciclados mixtos no cumplen por escaso margen algunas de las especificaciones, debido a un alto contenido de compuestos de azufre y a una menor resistencia a la fragmentación. El precribado de la fracción fina antes de la trituración de los RCD mixtos reduce el contenido de azufre total y mejora la calidad, por el contrario, el precribado de los RCD de hormigón no tiene ningún efecto sobre la calidad de los áridos reciclados. Los resultados se compararon con una zahorra artificial caliza como árido naturalSeven different types of recycled aggregates from construction and demolition waste (CDW) have been evaluated as granular materials for unbound road subbases construction. The results showed that recycled concrete aggregates complied with all specifications for using in the construction of unbound structural layers (sub-base) for T3 and T4 traffic categories according to the Spanish General Technical Specification for Road Construction (PG-3). Some mixed recycled aggregates fell short of some specifications due to a high content of sulphur compounds and poor fragmentation resistance. Sieving off the fine fraction prior to crushing the mixed CDW reduce the total sulphur content and improve the quality of the mixed recycled aggregates, by contrast, pre-sieving concrete CDW had no effect on the quality of the resulting aggregates. The results were compared with a crushed limestone as natural aggregate

Wastes as Aggregates, Binders or Additions in Mortars: Selecting Their Role Based on Characterization

The production of waste has increased over the years and, lacking a recycle or recovery solution, it is forwarded to landfill. The incorporation of wastes in cement-based materials is a solution to reduce waste deposition. In this regard, some researchers have been studying the incorporation of wastes with different functions: aggregate, binder and addition. The incorporation of wastes should take advantage of their characteristics. It requires a judicious analysis of their particles. This research involves the analysis of seven industrial wastes: biomass ashes, glass fibre, reinforced polymer dust, sanitary ware, fluid catalytic cracking, acrylic fibre, textile fibre and glass fibre. The main characteristics and advantages of each waste are enunciated and the best type of introduction in mortars is discussed. The characterization of the wastes as particles is necessary to identify the most suitable incorporation in mortars. In this research, some wastes are studied with a view to their re-use or recycling in mortars. Thus, this research focuses on the chemical, physical and mechanical characterization of industrial wastes and identification of the potentially most advantageous type of incorporation

Feasibility of Using Unbound Mixed Recycled Aggregates from CDW over Expansive Clay Subgrade in Unpaved Rural Roads

Social awareness aims to increase practical skills, such as sustainable development, which seeks to increase the use of different types of waste in construction activities. Although insufficient attention is sometimes given to these actions, it is essential to spread information regarding new studies in the field of waste recycling, which encourages and promotes waste use. Reusing and recycling construction waste in the creation of buildings and infrastructure are fundamental strategies to achieving sustainability in the construction and engineering sectors. In this context, the concept of waste would no longer exist, as waste would become a material resource. Therefore, this study analyses the behaviours of two unbound mixed recycled aggregates (MRA) in the structural layers of an unpaved rural road with low traffic (category T43). The sections were built on inappropriate soil (A-7-6) with a high degree of free swelling. The experimental road consisted of three sections: the first was made with natural aggregates (NA) that were used as a control, the second was composed of MRA in the subbase and NA in the base, and the third section was completely composed of MRA. The materials were characterised in the laboratory. The behaviours of the structural layers in the experimental road were determined by controlling compaction (“in situ” density and moisture) and measuring the deflections and load capacity (deflectometer) during the 18 months after construction. The results show that the sections made with recycled aggregates meet the technical specifications required by General Technical Specifications for Road and Bridge Works (PG-3). Therefore, the water-soluble sulphate content and Los Angeles abrasion coefficient limits can be increased for recycled aggregates without compromising the quality of this type of road with low traffic. To the best of our knowledge, this is the first study regarding the use of unbound MRA made from construction and demolition waste (CDW) in the construction of an unpaved rural road with low traffic on an expansive clay subgrade

Caracterización y posibilidades de reutilización en obras de infraestructura de los RCD's procedentes de la demolición de la prisión provincial de Córdoba

Comunicación presentada al III Congreso de Ingeniería Civil, Territorio y Medio Ambiente, Zaragoza, 2006El presente trabajo ha permitido la caracterización de los residuos de construcción y demolición (RCD’s) procedentes del derribo de la cimentación de la antigua Prisión Provincial de Córdoba. Tras una trituración primaria y secundaria, los materiales son sometidos a una trituración con molino de impactos que reduce el material a granulometrías inferiores a 50 mm, posteriormente el material es transportado hasta una criba vibrante de dos tamices que permite obtener tres fracciones de árido reciclado: 0-10 mm, 10-40 mm y mayor de 40 mm. Para la identificación de cada una de las fracciones se han realizado ensayos en laboratorio de granulometría, plasticidad, contenido en materia orgánica, contenido en sales y yesos, hinchamiento y colapso. Para caracterizar su comportamiento se han realizado principalmente ensayos Proctor e índice C.B.R. Los resultados obtenidos han puesto de manifiesto su excelente comportamiento mecánico y su elevada capacidad de soporte, sin embargo de acuerdo con el contenido en sales solubles y yesos el material se clasifica como suelo tolerable según el Pliego de Prescripciones Técnicas Generales para Obras de Carreteras y Puentes (PG-3). El árido reciclado 10-40 mm no cumple las condiciones granulométricas para su utilización en rellenos tipo terraplén según el PG-3, y se propone continuar la investigación realizando mezclas a distintos porcentajes de las fracciones 0-10 mm y 10-40 mm

Combined Effects of Non-Conforming Fly Ash and Recycled Masonry Aggregates on Mortar Properties

This work evaluates the effects of using non-conforming fly ash (Nc-FA) generated in a thermoelectric power plant as filler material for mortars made with natural sand (NA) and recycled sand from masonry waste (FRMA). The incorporation of powdered recycled masonry filler (R-MF) is also tested as an alternative to siliceous filler (Si-F). Three families of mortars were designed to study: the effect of replacing Si-F with Nc-FA on mortars made with NA; the effect of replacing Si-F with Nc-FA on mortars made with 50% of NA and 50% of FRMA; and the effect of replacing Si-F with R-MF on mortars made with NA and FRMA. Replacing Si-F with Nc-FA is a viable alternative that increases the mechanical strength, the workability and durability properties and decreases the shrinkage. The use of FRMA and Nc-FA improved the mechanical strength of mortars, and it slightly increased the shrinkage. The replacement of Si-F with R-MF on mortars made with FRMA is not a good alternative, because it has a negative impact on all of the properties tested. This work can help both to reduce cement and natural resources’ consumption and to increase the recycling rate of Nc-FA and FRM

Motivation of student learning through the gamification technique in Engineering Degrees, evaluation of performance-fatigue variables

Este trabajo pretende mejorar el proceso de enseñanza-aprendizaje de diferentes asignaturas del Grado en Ingeniería Civil y del Grado en Ingeniería de Recursos Energéticos y Minería de la Universidad de Córdoba (España), con el uso de prácticas docentes innovadoras que mejoren el rendimiento académico resultados de los estudiantes. La introducción de la técnica de gamificación ha permitido una participación más activa de los estudiantes y ha fomentado la adquisición de habilidades, así como el aprendizaje en un ambiente más relajado. El clima de trabajo se ha mantenido más activo. Además, esta técnica ha permitido detectar el punto de fatiga de los alumnos durante las clases. La herramienta utilizada para implementar la técnica de gamificación y evaluar el nivel académico de los alumnos durante las clases ha sido el acceso gratuito a la plataforma web "Kahoot", que es un sistema de respuestas en el aula basado en juegos para escuelas, universidades y empresas. Puede descargarlo en sus dispositivos electrónicos y / o acceder a él a través de su sitio web (https://kahoot.it/#/). Con esto, los estudiantes han utilizado sus teléfonos móviles o dispositivos electrónicos para contribuir a su aprendizaje en el Aula, y dejar de lado su uso inapropiado (redes sociales, noticias deportivas, etc.), evitando uno de los principales problemas que los profesores tienen actualmente en clase. Para cada conferencia, los cuestionarios en línea se llevaron a cabo utilizando la plataforma de aprendizaje Kahoot compuesta de preguntas asociadas con los conceptos teóricos / prácticos dados. Este procedimiento ha permitido una evaluación continua del alumno, e indirectamente del profesor, ya que se verifica en tiempo real si hay algún concepto que deba reforzarse. Mientras se llevaban a cabo los cuestionarios, se ha observado que los mismos estudiantes han participado en la aclaración de posibles preguntas de sus compañeros e incluso han hecho que el profesor reconsidere la forma de explicar y presentar la lección, lo que demuestra que esta técnica ha promovido la retroalimentación entre alumno-maestro y estudiante-alumno, fomentando un buen clima de trabajo y terminando las sesiones de una manera divertida, lo que ha permitido aumentar el rendimiento del alumno. Los resultados obtenidos han reflejado una evaluación final positiva de la asignatura para la mayoría de los alumnos que han participado en las clases. Con respecto a los cursos anteriores, los estudiantes han tenido menos dificultades para aprobar el tema y en la adquisición de habilidades. Es importante resaltar el grado de satisfacción de los alumnos, y en especial de los alumnos que repiten la asignatura, que han logrado aprobar el tema de una manera más fácil gracias al uso de técnicas de gamificación.This work hopes to improve the teaching-learning process of different subjects of the Degree in Civil Engineering and of the Degree in Engineering of Energy Resources and Mining at the University of Córdoba (Spain), with the use of innovative teaching practices that improve the academic results of the students. The introduction of the gamification technique has allowed a more active participation of students and has encouraged the acquisition of skills, as well as learning in a more relaxed environment. The work climate has remained more active. In addition, this technique has made it possible to detect the point of fatigue of the students during the lectures. The tool used to implement the gamification technique and evaluate the academic level of the students during the classes has been free access to the web platform "Kahoot, which is a system of answers in the classroom based on games for schools, universities and companies. Students can download it on their electronic devices and/or access it through its website (https://kahoot.it/#/). With this, the students have made use of their mobile phones or electronic devices to contribute to their learning in the classroom, and put aside their inappropriate use (social networks, sports news, etc.), avoiding one of the main problems that teachers have in class currently. For each lecture, the online questionnaires were carried out using the Kahoot learning platform composed of questions associated with the theoretical/practical concepts given. This procedure has allowed a continuous evaluation of the student, and indirectly of the teacher, since it is verified in real time if there is any concept that needs to be reinforced. While the questionnaires were carried out, it has been observed that the students themselves have participated in the clarification of possible questions from their classmates, and have even made the teacher reconsider the way of explaining and presenting the lesson, which shows that this technique has promoted the feedback between student-teacher and student-student, encouraging a good working climate and ending the sessions in a fun way, which has allowed to increase the student's performance. The results obtained have reflected a final positive evaluation of the subject for the most of students who have participated in the lectures. With respect to past courses, students have had less difficulty in passing the subject and in the acquisition of skills. It is important to highlight the degree of satisfaction of the students, and especially of the repeating the subject students, who have achieved to pass the subject in an easier way thanks to the use of gamification techniques

Upscaling the Use of Mixed Recycled Aggregates in Non-Structural Low Cement Concrete

This research aims to produce non-structural concrete with mixed recycled aggregates (MRA) in upscaled applications with low-cement content. Four slabs were executed with concrete made with different ratios of coarse MRA (0%, 20%, 40% and 100%), using the mix design, the mixing procedures and the facilities from a nearby concrete production plant. The analysis of the long-term compressive and splitting tensile strengths in concrete cores, extracted from the slabs, allowed the highlighting of the long-term high strength development potential of MRA incorporation. The study of cast specimens produced in situ under the same conditions as the slabs showed, firstly, that the use of MRA has a great influence on the properties related to durability, secondly, that the loss of compressive strength for total MRA incorporation relative to control concrete increases proportionally with the class strength, and, thirdly, that the mechanical properties (including Schmidt hammer results) from the concrete slabs showed no significant differences relative to the control concrete for coarse aggregates replacements up to 40%. Therefore, this upscaled experimental study supports the application of concrete with 100% coarse MRA incorporation and low cement content in non-structural civil works such as bike lanes, gutters, ground slabs, leveling surfaces, and subgrades for foundations. To the best of the authors’ knowledge, there have not been any upscaled applications of concrete with MRA and low cement conten