Estudio de la escoria de acería de hae - aspectos expansivos y ambientales -
- Autores: Miren Karmele Otegui Alday
- Directores de la Tesis: Marilda Barra (dir. tes.), Diego Fernando Aponte Hernández (codir. tes.)
- Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2019
- Idioma: español
- Tribunal Calificador de la Tesis: Enric Vazquez Ramonic (presid.), Carlos Thomas García (secret.), Francisco Agrela Sainz (voc.)
- Programa de doctorado: Programa de Doctorado en Ingeniería de la Construcción por la Universidad Politécnica de Catalunya
- Materias:
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- Resumen
Electric Arc Furnace Slag (EAFS) is the by-product generated in the steel making process in electric arc furnaces. According to the European slag association, EUROSLAG, 18,4Mt of steel slag have been reported, of which 32,2% comes from EAF, in Europe in 2016.
The steel slags present similar properties to the natural aggregate, enabling the use of EAFS in construction. In Europe in 2016, 46% of steel slag has been used in road construction, and 14,1% has been dumped.
In different experiences using steel slags in construction, it has been found that they could potentially present volumetric instability, compromising the durability of the executed works. Likewise, the use of steel slags in construction might cause the contamination of the environment due to the leaching of the heavy metals they contain. Following the guidelines set by the European Commission towards a circular economy, it is important to carry out the Life Cycle Assessment (LCA) of the management and/or use alternatives of the slags, to select the option with the least environmental impact through an objective methodology such as the LCA.
In this thesis the knowledge of the expansion and leaching phenomena and LCA of the EAFS is investigated, in order to use the steel slags in a safe and durable way in construction. Starting with an EAFS sample with an initial swelling, measured according to UNE-EN 1744-1, greater than 3,5% in volume, the study of the expansion is approached in two ways. On the one hand, a characterization of the EAFS microstructure is done to know the causes of expansion using different analytical techniques (FRX, free lime content, TGA, DRX, SEM-EDS, EPMA and MIP).
On the other hand, the potential swelling of slag is studied by quantifying the volumetric deformation by means of standardized laboratory tests (UNE-EN 1744-1 and ASTM D4792) and simulating the application of the EAFS as filling material in a confined state, under controlled conditions in a humidity chamber and outdoors. In addition, following George Wang's expansion force quantification model, a system capable of measuring the EAFS expansion force is designed, developed and implemented. It has been possible to determine the swelling pressure exerted by the EAFS with the mentioned expansion force equipment. Concrete is manufactured with EAFS to evaluate the consequences of the EAFS’ swelling in a rigid matrix.
For the leaching study, the total amounts of pollutants in the EAFS are obtained by the extraction method with aqua regia (ISO 11466:1995); matching the results in the compliance leaching test (UNE-EN 12457-2) with the limits imposed in the Decree 32/2009, on the recovering of steel slag in Catalonia, it is confirmed that EAFS are environmentally recoverable. With the pH-dependence (Method 1313) characterization test, the EAFS’s capacity on acid or base neutralization of the environment is achieved, and the emissions in different basic or acidic media are quantified. With the percolation test (BS EN 14405:2017), the main mechanism for the release of pollutants from EAFS are found.
The potential swelling and leaching of EAFS are evaluated in fresh state and at 18 months of outdoors weathering action, in addition to checking the effect of the carbonation of the material in the leachate.
Finally, the Life Cycle Assessment (LCA) of 1t of EAFS production in Adec Global S.L. recovery plant, and the delivery of material on site for the construction of 1m3 of sub-ballast, which was built in L'Hospitalet de Llobregat, are done. The assessment is carried out with Simapro, using the CML-IA method, with real data from the valorization plant, real consumptions in the building of the railroad and additional data from the Ecoinvent database.
