Valorización de residuos inorgánicos para la obtención de materiales de construcción

Abstract

Waste generation, in general, increases with technological development, consequently the interest in environmental protection and health risks have grown in recent years. Therefore, it is necessary to develop strategies that has a beneficial impact on waste reuse and management trying to achieve sustainable development in which the resources used and the waste generated are minimised, as well as trying to achieve a circular economy, incorporating waste and co-products to new materials. This approach has already been included in the European Union waste strategies, prioritizing the prevention in waste generation, as well as the recycling and valorisation of wastes as alternative to their landfilling disposal. The main objective of this Doctoral Thesis was born out of the need to develop new efficient applications with commercial interest as construction materials (ceramics, cement and bricks), depending on the percentage of three types of inorganic residues: (1) Ilmenite mud generated in the production of TiO2 pigment, (2) phosphogypsum from the H3PO4 industry, and (3) construction and demolition waste (CDW). A number of instrumental techniques were deployed to characterise both the wastes used and the new materials designed, such as, X-ray diffraction (XRD), X-ray fluorescence (XRF), inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectrometry (ICP-OES), thermo-gravimetric analysis and differential scanning calorimetry (TGA/DSC) and scanning electron microscopy (SEM). In addition, the technological properties, such as resistance, water absorption, etc., have been compared in relation to traditional commercial materials and evaluated according to the established technical standards. Since, some of the wastes are considered NORM (Naturally Occurring Radioactive Material), the materials obtained were evaluated by alpha and gamma spectrometry, and the environmental implications (leaching and radiological studies) were evaluated. The most prominent findings of the present research can be divided under three main headings: Ilmenite mud Once the physical, chemical, granulometric, micro-structural and radiological properties of this waste were known, the design of new sulphur polymer cements and ceramic bodies adding different percentages were carried out. The results shown that ilmenite mud could be successfully immobilised and valorised as an additive. Theirs technological properties are in agreement with the requirements established in each regulations and, in some cases, the results were even better than those obtained by the reference materials. Finally, it can be concluded that that both materials can be used with negligible environmental impact or health risk. Phosphogypsum This waste has been valorised as an additive in ceramic manufacturing, complying with the international regulations for both technological properties and environmental requirements. Moreover, the addition up to 5 wt.% of phosphogypsum improves the technological properties in relation to the reference material. In addition, this waste has been studied as a calcium source for CO2 mineral sequestration and calcite production with high efficiencies (96 %). The study of the fluxes of metals and radionuclides showed that most of the phosphogypsum pollutants are transferred to calcite (> 95%). Construction and demolition waste (CDW) This waste has been recycled as substitute of natural aggregates to produce bricks. The results shown that low cost bricks with excellent technological properties can be obtained using CDW as an aggregate and lime or cement, as binders.