This article addresses the preparation of a concrete using recycled aggregates obtained from the rubble recovery of concrete and masonry works. The study shows some aspects such as: compressive strength at 3, 7, 14, 28, 56 and 91 days; porosity, ultrasonic pulse speed and carbonation; economic costs compared to a conventional concrete; and a review of the public policies on sustainable construction and the use of rubble, in the city of Medellin, Colombia. For some mixes, the compressive strength and the ultrasonic pulse speed measurements were approximately the 98% of that of the reference mix. Likewise, the mix prepared with 100% of recycled aggregates showed a difference in the carbonation deepness of only 0.7 mm compared with the mix of reference for a simulated age of 27 years. The results obtained with the replacement of natural coarse and fine aggregates in 25%, 50%, and 100%, and the advance in the political-administrative guidelines of the city in the last eleven years, allow deducing the possibility of preparing structural and non-structural concretes for massive use in the construction area.

La fotografía como herramienta para el desarrollo de la creatividad y la alfabetidad visual: investigación en el aula

This study shows the modification of the cone of Abrams. A new device size was obtained, with 68% savings in terms of the material. Similarly, we explored the contribution to the aspect of occupational health since, from an ergonomic perspective, the test can be developed at a more comfortable and safe height for the person. Furthermore, we found equivalence between the ranges of the Abrams cone and the Bedoya cone. According to the tests performed, it is possible to significantly reduce the consumption of materials for the slump test without affecting the quality of the result. It improves the ergonomics condition of laboratory workers, especially for women who are not allowed to lift heavy loads due to occupational health regulations. More than 60 tests were carried out in universities, construction sites, precast industries and nationally and internationally accredited laboratories. The methodology used consisted of carrying out the test using the same mixture and finding the slump with the Abrams cone and the Bedoya cone simultaneously under the same conditions of temperature, time and humidity. One important aspect is the possibility of using in mixtures with coarse aggregates of sizes 9.5 mm (3/8''), 13 mm (1/2''), 19 mm (3/4''), and 25.4 mm (1''), being these the most commercially made worldwide. The results and the statistical analysis allow us to conclude that it is possible to use the Bedoya cone to determine the concrete slump in the fresh state, since its ranges are directly applicable with respect to the Abrams cone. As it is a test that continues to be carried out daily in all countries of the world, this research is also a social and environmental contribution. The cone of Bedoya is registered in Colombia under the patent of invention number NC2016/0001514, and is being applied in Undergraduate, Master's and Doctorate research in this country and in México.

Este artículo da a conocer un ejercicio pedagógico y didáctico, desarrollado desde el año 2009 en la facultad de Arquitectura de la Universidad Nacional de Colombia, Sede Medellín, mediante el cual se rescata y aborda el concepto de la Naturaleza en la enseñanza de los programas de Arquitectura, Ingeniería y Construcción. Esta experiencia que combina investigación, docencia y reflexión cultural, ha generado una posición crítica sobre el ejercicio enseñanza-aprendizaje en una época que pareciera privilegiar la imagen del proyecto y la figuración social en desmedro de los conceptos técnicos y del equilibrio eco-sistémico urbano y rural. Los resultados obtenidos en cuanto a participación de estudiantes, multiculturalidad e interdisciplinariedad son alentadores; para ello se tomaron los datos estadísticos de estudiantes y sus programas curriculares, infiriendo con ello un posible impacto en la comunidad universitaria y, aún más importante, en el ecosistema urbano del área metropolitana cuya capital es Medellín.