Jessica Giro-Paloma

Use of weathered and fresh bottom ash mix layers as a subbase in road constructions: environmental behavior enhancement by means of a retaining barrier.

The presence of neoformed cement-like phases during the weathering of non-stabilized freshly quenched bottom ash favors the development of a bound pavement material with improved mechanical properties. Use of weathered and freshly quenched bottom ash mix layers placed one over the other allowed the retention of leached heavy metals and metalloids by means of a reactive percolation barrier. The addition of 50% of weathered bottom ash to the total subbase content diminished the release of toxic species to below environmental regulatory limits. The mechanisms of retention and the different processes and factors responsible of leaching strongly depended on the contaminant under concern as well as on the chemical and physical factors. Thus, the immediate reuse of freshly quenched bottom ash as a subbase material in road constructions is possible, as both the mechanical properties and long-term leachability are enhanced.

Geopolymers based on the valorization of Municipal Solid Waste Incineration residues

The proper management of Municipal Solid Waste (MSW) has become one of the main environmental commitments for developed countries due to the uncontrolled growth of waste caused by the consumption patterns of modern societies. Nowadays, municipal solid waste incineration (MSWI) is one of the most feasible solutions and it is estimated to increase in Europe where the accessibility of landfill is restricted. Bottom ash (BA) is the most significant by-product from MSWI as it accounts for 85 95 % of the solid product resulting from combustion, which is classified as a non-hazardous residue that can be revalorized as a secondary aggregate in road sub-base, bulk lightweight filler in construction. In this way, revalorization of weathered BA (WBA) for the production of geopolymers may be a good alternative to common reuse as secondary aggregate material; however, the chemical process to obtain these materials involves several challenges that could disturb the stability of the material, mainly from the environmental point of view. Accordingly, it is necessary that neoformed geopolymers are able to stabilize heavy metals contained in the WBA in order to be classified as nonhazardous materials. In this regard, the SiO2/Al2O3 ratio plays an important role for the encapsulation of heavy metals and other toxic elements. The aim of this research is to formulate geopolymers starting from the 0 2 mm particle size fraction of WBA, as a unique raw material used as aluminumsilicate precursor. Likewise, leaching tests of the geopolymers formulated were performed to assess their environmental impact. The findings show that it is possible to formulate geopolymers using 100 % WBA as precursor, although more investigations are needed to sustain that neoformed geopolymer obtained can be considered as non-hazardous materials.

Physical, thermal and mechanical study of MPC formulated with LG-MgO incorporating Phase Change Materials as admixture

The high environmental impact generated by using of Ordinary Portland Cement (OPC) has lead to the search for alternative materials in the field of civil and building engineering. In addition, there is a tendency to develop cements from industrial by-products, thus reducing pollution and emissions generated by their production. One of the best positioned cements to compete with OPC is Magnesium Phosphate Cement (MPC). The present work studies different dosages of MPC mortars formulated with low-grade MgO by-product (sustainable MPC) incorporating Microencapsulated Phase Change Materials (MPCM) and air entraining additive (AEA) as admixtures (Thermal Sustainable MPC) to improve the thermal behaviour of the material. The aim is developed a new eco-friendly material that leads to reducing energy consumption in buildings. The study is focused on the physical, thermal, and mechanical characterization of TS-MPC mortars to assess their potential use as a thermal prefabricated panel. The results allow to relate the amount of the MPCM and the additive percentage with the thermal and mechanical properties of the TSMPC. Furthermore, is important to highlight the influence of MPCM not only in the thermal behaviour but also on the increase of the porosity. The experimental results show that the addition of both additives contributes substantially to the improvement of the thermal behaviour of the mortars and converts them on a suitable material to reduce thermal oscillations in buildings.

Use of municipal solid waste incineration bottom ash and crop by-product for producing lightweight aggregate

Due to the growing amount of residues in Europe, it is mandatory to provide a viable alternative for managing wastes contributing to the efficient use of resources. Besides, it is also essential to move towards a low carbon economy, priority EU by 2050. Among these, it is important to highlight the development of sustainable alternatives capable of incorporating different kind of wastes in their formulations.Municipal Solid Waste Incineration (MSWI) is estimated to increase in Europe, where the accessibility of landfill is restricted. Bottom ash (BA) is the most significant by-product from MSWI as it accounts for 85 - 95 % of the solid product resulting from combustion. BA is a mixture of calcium-rich compounds and others silicates enriched in iron and sodium. In addition, it is categorized as non-hazardous waste which can be revalorized as secondary material in construction or civil engineering fields, previous weathering stabilization during 2 - 3 months. Taking into account the relative proportion of each size fraction and the corresponding material characterization, the content of glass (primary and secondary) is estimated to be around 60 wt%. Furthermore, as a renewable resource and according to waste management European policies, residual agricultural biomass has attracted attention in preparation of advanced materials for various applications, due to their low cost, abundance, and environment friendliness. Among this residual biomass, rice husk is a by-product of rice milling industry which has high content of silica and has been widely used in buildings as natural thermal insulation material.Weathered BA (WBA) with a particle size less than 30 mm was milled under 100 μm, mixed with 2.0 - 5.0 mm rice husk, formed into ball-shaped pellets and sintered by different thermal treatments, which remove the organic matter content generating a large porosity. Physico-chemical analysis and mechanical behavior of the manufactured lightweight aggregates were tested. The obtained results provide a suitable physico-mechanical formulation using WBA as silica source, as well as a common crop by-product.

APC fly ashes stabilized with Portland cement for further development of road sub-base aggregates

Although waste-to-energy plants allow reducing the mass and volume of municipal solid waste (MSW) incinerated, an average around 30 % of the total content remains as bottom ash (BA) and air pollution control (APC) ashes at the end of combustion process. While weathered bottom ash (WBA) is considered a non-hazardous residue that can be revalorized as a secondary aggregate, APC fly ashes generated during the flue gas treatment are classified as hazardous waste and are handled in landfill disposal after stabilization, usually with Portland cement (OPC). However, taking into account the amount of APC residues produced and the disposing cost in landfill, their revalorization is an important issue that could be effectively addressed. As MSW can be incinerated producing bottom ashes (BA) or air pollutant control (APC) residues, the development of a mortar formulated with APC fly ash as secondary building material is a significant risk to the environment for their content of heavy metals. In this way, Design of Experiment (DoE) was used for the improvement of granular material (GM) formulation composed by APC and OPC for further uses as road sub-base aggregate. DoE analysis was successful in the modelling and optimization the formulation as function of the mechanical properties and APC amount. Consequently, an optimal mortar formulation (OMF) of around 50 wt.% APC and 50 wt.% OPC was considered. The OMF leachates and abrasion resistance have been analyzed. These results have demonstrated the viability of OMF as non-hazardous material feasible to be used as secondary aggregate. Moreover, it would be possible to consider the environmental assessment of a GM composed by ≈20 wt.% of OMF and ≈80 wt.% of WBA in order to improve mechanical properties and heavy metals stabilization.