Síntesi i caracterització de Ciments Activats Alcalinament basats en Escograva i Paval

Treballs Finals de Grau d'Enginyeria de Materials, Facultat de Química, Universitat de Barcelona, Any: 2018, Tutors: Josep Mª Chimenos i Ribera, Alex Maldonado AlamedaOne of the most important challenges of European Union (EU) is to reduce the amount of municipal waste and industrial by-products generated since they are one of the main threats to the environment. For this reason, the valorisation of this waste and by-products has emerged, to produce compatible and viable products. If we focus on construction materials, some of these waste and by-products that have a large SiO2, Al2O3 and CaO content can be used to produce cements. Alkali Activated Cements (AAC) stands out as one of the best choices to produce this cements, since they can compete with Portland cements and they are also more sustainable. The main purpose of this project is to synthetize and study AAC based in two by-products: municipal waste incineration bottom ash and Paval, an industrial by-product generated in aluminium production, by using as alkaline activators NaOH and Na2SiO3. The results obtained in this project demonstrate that with this two by-products it is possible to synthetize AAC, and that their mechanical properties are good enough to study them in more detail to make them a real alternative to Portland cements. Different formulations have been considered by changing the proportions of this by-products and the alkali activators to determine which formulation gives rise to best results. It has been concluded that the AAC synthetized with bottom ash and 10% of Paval and activated with NaOH 6M are the formulations that give rise to better propertie

Evaluation of mechanically activated kaolin as alkali-activated material precursor

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Sustainable asphalt mixtures by partial replacement of fine aggregates with low-grade magnesium carbonate by-product

The utilisation of large quantities of raw materials for asphalt mixtures manufacturing, such as aggregates, is an environmental issue that must be addressed. This concern has led to valorising waste and by-products as more sustainable alternative raw materials. This research is aimed at evaluating the use of a low-grade magnesium carbonate (LG-MC) by-product as a partial replacement of fine aggregates and as a filler of asphalt mixtures. A mechanical analysis has been performed studying the effect of this by-product on the moisture sensitivity, cracking resistance and cohesion loss resistance of asphalt mixtures. Cracking resistance was assessed under different temperatures (20, 5 and -5 ºC) and conditions (unconditioned and aged). Results indicated that moisture sensitivity and cohesion loss resistance of asphalt mixtures with LG-MC by-product were not affected, obtaining similar results to those of the reference mixture. A protective effect in the mixture cracking resistance was observed using LG-MC. At low temperatures or after ageing, this by-product tends to maintain ductility to a greater extent. The study indicates that LG-MC is suitable as a partial substitute for the fine fraction of aggregates, as well as for the total amount of filler in asphalt mixtures manufacturing for road pavements

Alkali activated binders based on municipal solid waste Incineration bottom ash

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Structural characterisation and reactivity measurement of chemically activated kaolinite

This study examines the structural evaluation of differently activated kaolins for potential use as supplementary cementitious materials (SCM) or as precursor for alternative cementitious materials (ACM). Chemical activation involved amorphizing the kaolinite structure using varying phosphoric acid concentrations, reaction times, and temperatures. Metakaolin obtained via thermal activation served as a comparison. Inductively Coupled Plasma – Optical Emission Spectroscopy (ICP-OES) characterization of the activating solutions revealed phosphoric acid activation leading to dealumination in kaolinite structures, with temperature emerging as the most significant parameter. X-ray diffraction (XRD) confirmed amorphization, attributed to the dealumination process causing Al loss and creating new Si–O–Si interlayered bonds, as monitored by 29Si magic-angle spinning nuclear magnetic resonance (MAS NMR) tracking the change from Q3 to Q4 environments. Furthermore, pozzolanic activity was assessed through Ca(OH)2 consumption and reaction heat release via modified Chapelle and R3 tests, respectively. Kaolinite subjected to intensive chemical activation exhibited high reactivity and increased specific surface area, indicating its potential as a pozzolanic material. Keywords: Kaolin; Chemical activation; Supplementary cementitious materials; Alternative cementitious materials; Dealumination; Pozzolanic reactivity

Rapid sintering of weathered municipal solid waste incinerator bottom ash and rice husk for lightweight aggregate manufacturing and product properties

This study assessed the technical feasibility of formulating lightweight aggregates (LWA) from municipal solid waste incinerator bottom ash (IBA) and residual biomass. Weathered IBA (WIBA) particles larger than 8 mm contain a mixture of calcium-rich compounds and other silicates mainly composed of glass and synthetic and natural ceramics, with low contents of heavy metals and soluble salts. Unfired LWA were formulated with the particle size fraction of WIBA larger than 8mm and rice husk (RH) used as the bloating agent. Rapid sintering of the unfired spherical pellets at 1,100°C for 5min produced some cohesive sintered LWA, whose porosity, apparent particle density, water absorption, and compressive strength directly correlated with the percentage of RH added. The fired LWA formulated with 5wt% of RH showed the highest bloating index (115%) and porosity (53%) and the lowest apparent particle density (0.61Mgm−3) and compressive strength (1.4MPa). The addition of more than 5wt% of RH increased the internal temperature of the sintered aggregates and decreased the viscosity of the molten glassy materials, resulting in the collapse of the inner structure. Consequently the porosity decreased and the apparent density of the particles increased, thereby shrinking the volume of the fired LWA. According to the standard leaching test (EN 12457-4), both the unfired precursor and the sintered aggregates showed concentrations of heavy metals and metalloids in the leachates that were well below the safety limits established for their reuse as secondary material

High-porosity alkali-activated binders based on glass and aluminium recycling industry waste

The potential as alkali-activated precursors of ceramic-stone-porcelain (CSP) and PAVAL, two residues derived from the optical separation of glass cullet and salt slag from secondary aluminium recycling, has been assessed. Alkali-activated CSP and PAVAL binders’ formulations were prepared using NaOH 4 M and 6 M as alkaline activator solutions. The effect of the Na2O/Al2O3 ratio and alkaline activator concentration was evaluated from a chemical, physical, mechanical, and environmental perspective. The results revealed the formation of secondary reaction products attributed to the formation of (C,N)-A-S-H gels. It also showed the influence of decreasing Na2O/Al2O3 ratio in the obtained binders, increasing porosity and affecting the mechanical performance. Besides, it was demonstrated that PAVAL acts as a precursor and pore-generator. Finally, the environmental characterisation showed a significant leaching concentration of heavy metal(loid)s such as As, Cr, Mo, Sb, and Se, which decreases with longer curing periods.This work is partially supported by the Grants PID2021-125810OB-C21 and TED2021-129718B-I00, funded by MCIN/AEI/https://doi.org/10.13039/501100011033 , by “ERDF A way of making Europe”, and by the “European Union NextGenerationEU/PRTR”, and the Agència de Gestió d’Ajuts Universitaris i de Recerca (AGAUR) with the Grant 2021 SGR 00708. The authors would like to thank Daniel Rosas, S.A. for supplying the CSP, and Befesa Company for supplying the PAVAL. Mr Jofre Mañosa is grateful to the Government of Catalonia for its research Grant (FI-DGR 2020). Dr Teresa López-Montero is supported by the Spanish grant Juan de la Cierva Formación referenced as FJC-2018-035747-I.Peer ReviewedPostprint (published version

Alkali-activated binders using bottom ash from waste-to-energy plants and aluminium recycling waste

Alkali-activated binders (AABs) stand out as a promising alternative to replace ordinary Portland cement (OPC) due to the possibility of using by-products and wastes in their manufacturing. This paper assessed the potential of weathered bottom ash (WBA) from waste-to-energy plants and PAVAL® (PV), a secondary aluminium recycling process by-product, as precursors of AABs. WBA and PV were mixed at weight ratios of 98/2, 95/5, and 90/10. A mixture of waterglass (WG) and NaOH at different concentrations (4 and 6 M) was used as the alkaline activator solution. The effects of increasing NaOH concentration and PV content were evaluated. Alkali-activated WBA/PV (AA-WBA/PV) binders were obtained. Selective chemical extractions and physicochemical characterization revealed the formation of C-S-H, C-A-S-H, and (N,C)-A-S-H gels. Increasing the NaOH concentration and PV content increased porosity and reduced compressive strength (25.63 to 12.07 MPa). The leaching potential of As and Sb from AA-WBA/PV exceeded the threshold for acceptance in landfills for non-hazardous waste

Alkali-activated binders based on the coarse fraction of municipal solid waste incineration bottom ash

The potential of the least polluted fraction (from 8 to 30mm) of municipal solid waste incineration (MSWI) weathered bottom ash (WBA) as an alkali-activated cement precursor was evaluated. Alkali-activated WBA binders (AA-WBA) formulations were prepared through alkali-activation of WBA as sole precursor. Sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) mixtures with different pH's were used as alkali-activator solution. The effect of alkali-activator solution pH on the final properties was assessed. Results showed the hydrolytic stability of allformulations. The selective chemical extractions and physicochemical characterisation revealed the formation of the C-S-H, C-A-S-H, and (N,C)-A-S-H gels. The promising compressive strength results demonstrated the potential of AA-WBA binders. The increase of pH in the alkali-activated solution promotes the formation of gel reaction products and enhance mechanical properties. This investigation promotes the green cements manufacturing and the use of secondary resources to reduce the impact of natural resources extraction used for the ordinary Portland cement (OPC) production

Pyroclastic volcanic ash as a potential precursor of alkali-activated binders - A case study from Tajogaite (La Palma, Canary Islands) volcano eruption

The volcanic eruption of Tajogaite in La Palma (Canary Islands, Spain) produced approximately 200 Mm3 of fine lapilli and ash. Using this volcanic ash (VA) to produce alkali-activated binders (AABs) fosters a sustainable approach to binder manufacturing, aligning with the principles of a circular economy and reducing reliance on non-renewable resources. The feasibility of using VA as a sole precursor for the formulation of sustainable AABs was evaluated based on its composition and physical-chemical properties. To this end, a comprehensive physicochemical characterization of VA was carried out and the physical, mechanical, and environmental properties of the binders formulated were analyzed. The physical-chemical analysis reveals the neoformation of typical secondary reaction products, such as NASH and (C,N)ASH gels. The microstructure analysis reveals that the AABs formulated using 6 M and 8 M NaOH activator solutions contain homogeneously dispersed unreacted VA particles within the binder matrix, providing increased cohesion and mechanical strength. The highest compressive resistance of AABs formulated using only VA as the precursor was achieved with a 6 M NaOH activator solution and a curing temperature of 60 ◦C, reaching a strength of 16 MPa. Although alkaline activation enhances the release of some metals and metalloids contained in the VA, the study of the environmental requirements at the end of the life cycle of the formulated AABs allows them to be classified as nonhazardous materials