Life Cycle Assessment of Alkali Activated Cement compared to Ordinary Portland Cement

Approximately 8% of the global emissions of CO2 are originated by the cement industry, which consumes on average between 4 to 6 GJ per ton of cement. Ordinary Portland Cement (OPC) is the most used cement for construction purposes. Every year, around 4 billion tonnes (Gt) of OPC are manufactured. For each kg of OPC produced, 0.81 kg of CO2 is generated. Therefore, seeking cements with more environmentally friendly manufacturing process, economically viable, and socially relevant is necessary. One of the most promising materials are the Alkali-Activated Cements (AAC), where its components are an aluminosilicate precursor and alkaline activators. The precursor used in this study is Weathered Bottom Ash (WBA), a waste obtained from the Municipal Solid Waste Incineration (MSWI). On the other hand, the alkaline activators are sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). The name of the AAC developed is Sustainable-AAC (Sust-AAC). This project is focused on searching for new materials that could reduce the use of OPC as a building material. To be able to assess the associated environmental impacts, a comparison between AAC and OPC (CEM I) through a Life Cycle Assessment (LCA) following the standards ISO 14040:2006 and ISO 14044:2006 is performed. The LCA methodology allows identification and quantification of relevant inputs and outputs of the system, thus, evaluating the potential environmental impacts associated. The system boundary of this project is cradle-to-gate and the functional unit of the assessment is 1 ton of commercial cement. The OPC inventory is carried out through the values obtained in GaBi Software and the Sust-AAC inventory is made from the previous studies performed in the DIOPMA research group, on a laboratory scale. The results show that the OPC has higher impact on global warming, energy consumption, water consumption, and mineral extraction categories compared to Sust-AAC. In OPC manufacturing, the kiln stage is the most energy intensive stage (by the chemical reaction and by the fossil fuel requirement) and therefore, has the most significant environmental impact in terms of CO2 emissions and energy consumption. In contrast, the highest environmental impacts on the Sust-AAC are due to the production of Na2SiO3. The main reason for the energysaving is because Sust-AAC production does not need a kiln with high temperatures. In addition, the use of waste as raw material promotes a circular economy and, at the same time, reduces the extraction of natural resources. Then, the environmental performance in the Sust-AAC is promising compared to OPC. Sust-AAC is suitable to be used as lightweight material and as insulation material for thermal insulating applications. This application can contribute to realising operational energy savings and performance benefits

Geopolymers based on the valorization of Municipal Solid Waste Incineration residues

he 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 geopolymers are able to stabilize heavy metals contained in the WBA in order to be classified as non-hazardous 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 geopolymer obtained can be considered as non-hazardous materials

Legal situation and current practice of waste incineration bottom ash utilisation in Europe

Almost 500 municipal solid waste incineration plants in the EU, Norway, and Switzerland generate about 17.6 Mt/a of incinerator bottom ash (IBA). IBA contains minerals and metals. Metals are mostly separated and sold to the scrap market and minerals are either disposed of in landfills or utilised in the construction sector. Since there is no uniform regulation for IBA utilisation at EU level, countries developed own rules with varying requirements for utilisation. As a result from a cooperation network between European experts an up-to-date overview of documents regulating IBA utilisation is presented. Furthermore, this work highlights the different requirements that have to be considered. Overall, 51 different parameters for the total content and 36 different parameters for the emission by leaching are defined. An analysis of the defined parameter reveals that leaching parameters are significantly more to be considered compared to total content parameters. In order to assess the leaching behaviour nine different leaching tests, including batch tests, up-flow percolation tests and one diffusion test (monolithic materials) are in place. A further discussion of leaching parameters showed that certain countries took over limit values initially defined for landfills for inert waste and adopted them for IBA utilisation. The overall utilisation rate of IBA in construction works is approximately 54 wt.%. It is revealed that the rate of utilisation does not necessarily depend on how well regulated IBA utilisation is, but rather seems to be a result of political commitment for IBA recycling and economically interesting circumstances

Preparation and exhaustive characterization of paraffin or palmitic acid microcapsules as novel phase change material

WOS: 000350191000030In this study, two different types of Phase Change Materials (PCM) suitable for Thermal Energy Storage (TES) applications were used as a core material in a microencapsulation process. The wall material for these microencapsulated PCM (MPCM) was Poly(styrene-co-ethylacrylate) (PScEA). Microcapsules were prepared using an emulsion co-polymerization technique. The prepared MPCM were characterized as follows: morphology, shape and size were analyzed by Scanning Electron Microscopy (SEM) and Particle Size Distribution (PSD). Besides, Fourier Transformed Infrared spectroscopy (FT-IR) was used to perform the chemical characterization of the shell microcapsules. Moreover, thermophysical properties were analyzed by Differential Scanning Calorimetry (DSC) for the two PCM in usage (paraffin 42-44 and palmitic acid) meanwhile the thermal stability was evaluated by Thermogravimetrical Analysis (TGA). Mechanical characterization of the prepared microcapsules was performed by using the Atomic Force Microscopy (AFM) as indentor. Experiments were performed at two different temperatures 25 degrees C and 70 degrees C, and two parameters were evaluated: the Young's modulus on a punctual area and the vertical force required to plastically deform the MPCM. At the light of the results, it can be considered that these synthesized MPCM were successfully prepared being able to be used in a TES system. (C) 2014 Elsevier Ltd. All rights reserved.Spanish government [ENE2011-28269-C03-02]; European Union's Seventh Framework Programme (FP7) [PIRSES-GA-2013-610692]; Scientific & Technical Research Council of Turkey (TUBITAK) [TUBITAK 111M614]The work is partially funded by the Spanish government (ENE2011-28269-C03-02). The authors would like to thank the Catalan Government for the quality accreditation given to their research group DIOPMA (2014 SGR 1543). The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement no PIRSES-GA-2013-610692 (INNOSTORAGE). Also, preparation of microcapsules funded by The Scientific & Technical Research Council of Turkey (TUBITAK) (The Project Code: TUBITAK 111M614)

Weathered bottom ash from municipal solid waste incineration: Alkaline activation for sustainable binders

Alkali-activated binders (AABs) stand out as promising candidates to replace ordinary Portland cement (OPC) since waste can be used as raw material for their manufacture. This study addresses the environmental feasibility of using weathered bottom ash (WBA) and metakaolin (MK) as alkali-activated binder precursors (AA-WBA/MK). Different proportions of WBA and MK were mixed (100/0, 75/25, 50/50, 25/75, and 0/100 wt%) with a mixture of waterglass (WG) and NaOH 8 M as an alkaline activator solution. The effect of increasing MK content was assessed from a chemical, physical, mechanical, and environmental perspective. The results revealed the formation of secondary reaction products of C-(A)-S-H, (C,N)-A-S-H, and N-A-S-H gels. The compressive strength of AA-WBA/MK binders decreased (from 61.6 MPa to 12.6 MPa) as the MK content increased. The monolithic tank test validated the use of AA-WBA/MK binders for construction purposes, although with some restrictions due to their content in As, Sb, and V. Finally, the encapsulation efficiency and mechanical performance of AA-WBA/MK binders was enhanced as the curing period increased

Water treatment sludge as precursor in non-dehydroxylated kaolin-based alkali-activated cements

Cement industry production and its materials demand are growing every year, leading to a CO2 and energy footprint increase. The drinking water production is increasing in water treatment plants due to the population growth, raising in turn the waste materials produced. Since these wastes are mainly managed in landfills, this preliminary research work is focused on providing a new sustainable option for valorisation processes, based on the environmental demand of the cement industry. Alkali-activated cements (AACs) can become a proper option to give the water treatment sludge a new life cycle, as they can compete with ordinary Portland cement (OPC) both in properties and sustainability. The main purpose of this study was to evaluate and formulate different AACs based on the use of both raw clay and the water treatment sludge (WTS), as precursors. The raw clay was used without previous thermal dehydroxylation treatment, and the WTS, an aluminosilicate-rich waste, was used partially replacing the raw clay in the AACs formulations. Both precursors and the formulated AACs were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF) and Fourier-transformed infrared spectroscopy (FT-IR). In addition, the compressive strength, the chemical stability (hydrolytic degradation), and the environmental impact for each AACs formulation were also determined. The results showed that AACs specimens formulated with 20 wt% of WTS (replacing the raw clay) provided the best results, considering both compressive strength and resistance to hydrolytic degradation. Then, it is possible to formulate AACs using raw clay, without prior thermal dehydroxylation treatment, and WTS as precursors. © 2021 Elsevier B.V