Cuantificacion mineralogica de cementos mediante analisis rietveld de Drx. analisis cruzado de difractogramas experimentales y programas de refinamiento : Mineralogical quantification of cements determined by Rietveld analysis of XRD : Cross analysis of experimental pattern and software for refinement

Existen varias técnicas para conocer la composición mineralógica de los cementos, como las fórmulas de Bogue o el conteo con microscopía. En los últimos años la técnica que ha ganado mayor aceptación es la cuantificación mediante el método Rietveld para difracción de rayos X, por sus ventajas comparativas a los demás métodos (velocidad, precisión y la posibilidad de ser aplicado a cualquier tipo de cemento). Entre las variables que pueden afectar a la reproducibilidad de los resultados, se encuentra el conocimiento y la experiencia del operario que utiliza los programas de refinamiento. Para minimizar la incidencia del operario existen protocolos de refinamiento, a veces incluidos en el programa, o como en este caso elaborados manualmente. En este trabajo se analizaron muestras de cementos y adiciones minerales con dos programas de refinamiento y se compararon los resultados entre sí, y con ensayos de fluorescencia

Complete re-utilization of waste concretes–Valorisation pathways and research needs

Global demand for buildings and infrastructure is extremely high as provision of shelter, sanitation and healthcare are paramount to safeguard the world's growing population. Concrete is a preferred construction material to meet this demand, but its production is leading to overexploitation of natural gravel and sand, causing an environmental crisis in regions where these materials are extracted unsustainably. Waste concrete is available globally, particularly in regions with fast growth of the built environment, and those struck by coordinated attacks, earthquakes or severe weather events. Waste concrete has mainly been used for producing recycled aggregates; however, its full recycling is still not practiced. Alternative uses include applications as fine recycled aggregates, supplementary cementitious materials, filler, and feedstocks for clinker production. These technologies still face challenges concerning their adoption and eco-efficiency. Restricted knowledge and operational barriers have also prevented implementation of beneficiation technologies for complete re-recycling of waste concretes, particularly the fine fractions produced during crushing. Despite these issues, it is recognised that the complete utilization of waste concrete offers unique opportunities for supply chain security, reducing natural resources consumption and enabling to move towards a Circular Economy. Harmonizing current practices for the treatment of waste concrete and the by-products generated during their processing, is a first step toward policy and standards development to enable their widespread use. This critical discussion addresses challenges and opportunities, as well as facilitation strategies needed to progress the complete re-utilization of waste concrete as a valuable resource for creating sustainable future infrastructure

External sulphate attack on recycled concrete: Assessment of the influence of recycled aggregate

The performance of recycled aggregate concrete (RAC) under external sulfate attack (ESA) has not been fully clarified yet. The attached mortar on recycled aggregate particles increases the content of hydration products from Portland cement that are able to react with external sulfates. In addition, it increases the porosity of the resulting material, facilitating the penetration of ions.In this paper, we present experimental results focusing on the evaluation of the potential reactivity of recycled aggregates themselves. Weight and length variations of mortar bars made with fine recycled aggregates obtained from crushing concretes containing high and low C3A Portland cements were determined after exposure to sulfate solution at 38ºC. In addition, concrete cores with 25 mm and 75 mm in diameter exposed to sulfate solution at 20ºC were also evaluated. The results show no indication of significant reactivity of recycled aggregates with external sulfate.Fil: Santillan, Lautaro Rodolfo. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Área Tecnología del Hormigón; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Villagrán Zaccardi, Yury Andrés. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Área Tecnología del Hormigón; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Zega, Claudio Javier. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Área Tecnología del Hormigón; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaRILEM Final Workshop of TC 251-SRTMadridEspañaInstituto de Ciencias de la Construcción Eduardo TorrojaThe International Union of Laboratories and Experts in Construction Materials, Systems and Structure