Departamento de Ingeniería Química, Ambiental y de los Materiales
URI permanente para esta comunidadhttps://hdl.handle.net/10953/42
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Ítem Acorn gasification char valorisation in the manufacture of alkali activated materials(Elsevier, 2023-09-30) Gómez-Casero, Miguel Ángel; Calado, Luís; Romano, Pedro; Eliche-Quesada, DoloresThe use of biomass for energy production is becoming increasingly common. An energy source with good prospects for the future is the gasification process of biomass waste. This process is characterized by the partial oxidation of the raw material at high temperatures, which converts the raw material into a mixture of combustible gases. However, one of the problems when using biomass is the ash produced in the gasification process. This study investigates the effect of the incorporation of ash generated in the production of syngas from biomass residues from the acorn industry on the physical, mechanical and thermal performance of electric arc furnace slag (EAFS) based alkaline activated cements for industrial applications. Acorn gasification ash (AGA) after a calcination process were used to replace EAFS at different substitution ratios: 0, 25, 50, 75 and 100 wt%. The influence of the modulus of the activator (Ms = SiO2/K2O = 0.89; 1.38 and 1.84) was also studied. The specimens were evaluated for density, porosity, flexural and compressive strength, thermal conductivity, X-ray diffraction analysis, infrared spectroscopy, and microstructure development at 1, 7, 28 and 56 days of curing. The results showed that the inclusion of up to 50 wt% AGA gives rise to cements with similar or higher compressive strength than the control cement containing only EAFS. The optimum activator modulus depends on the proportion of precursors used, increasing with increasing AGA content. Therefore, the activator ratio and AGA content are factors that must be considered simultaneously to achieve the optimum compressive strength. The main reaction product was C-(A)-S-H gel, and to a lesser extent K-(A)-S-H gel and C-K-(A)-S-H hybrid gel. This work suggests the use of AGA improve alkali activated metallurgical slag binders, partially substituting the conventional Portland cement as structural material.Ítem Comparative study of alkali activated cements based on metallurgical slags, in terms of technological properties developed(Elsevier, 2022-06-23) Gómez-Casero, Miguel Ángel; Pérez-Villarejo, Luis; Sánchez-Soto, Pedro José; Eliche-Quesada, DoloresIn this work, an investigation on the use of two slags from different origins (electric arc furnace slag (EAFS) and copper slag (CS)) as raw materials in the manufacture of alkali-activated cements has been carried out. A comparison of the different mechanical properties developed by the alkaline activation of each raw material has been studied. Combination of 35 wt% potassium hydroxide (KOH) solution with different concentration (5, 8, 12 and 15 M) and 65 wt% potassium silicate (K2SiO3) solution was used as activating solution to manufacture alkali activated cements. The pastes were cured 24 h in a climatic chamber at 20 °C at 90% of relative humidity, subsequently demoulded and cured at same condition during 1, 7, 28 and 90 days. Alkali activated materials have been characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The physical properties: bulk density, water absorption and apparent porosity, mechanical properties, flexural strength and compressive strength and thermal properties: thermal conductivity have been determined. The results indicate that two types of slags studied are a suitable source of aluminosilicates that can be activated for the manufacture of alkali-activated materials. These precursors are capable of developing high values of flexural and compressive strength and low values of thermal conductivity when optimal concentration of KOH was used. The optimal composition was developed when CS was utilized. Binders with CS and 12 M M ratio achieved compressive strength values up to 70 MPa.Ítem Effect of olive-pruning fibres as reinforcements of alkali-activated cements based on electric arc furnace slag and biomass bottom ash(Springer Nature, 2024-03-18) Gómez-Casero, Miguel Ángel; Sánchez-Soto, Pedro José; Castro-Galiano, Eulogio; Eliche-Quesada, DoloresIn this work, alkali-activated composites using electric arc furnace slag (50 wt%) and biomass bottom ash (50 wt%) were manufactured, adding olive-pruning fibres as reinforcement. The objective of adding fibres is to improve the flexural strength of composites, as well as to prevent the expansion of cracks as a result of shrinkage. For this reason, composites reinforced with olive-pruning fibres (0.5–2 wt%) untreated and treated with three different solutions to improve matrix–fibre adhesion were manufactured. Treatments developed over fibres were a 10 wt% Na2SiO3 solution, 3 wt% CaCl2 solution and 5 wt% NaOH solution. Mechanical properties, physical properties, thermal properties and the microstructure of composites by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were studied to demonstrate the improvement. Alkaline treatment degraded fibre surface, increasing the matrix–fibre adhesion, and as a consequence, flexural strength increased up to 20% at 90 days of curing. Optimal results were obtained with composites reinforced with 1 wt% of olive-pruning fibre treated by a 10 wt% Na2SiO3 solution. Higher quantity of olive-pruning fibre leads to local agglomeration, which weakens the matrix–fibre adhesion. The effect on the compressive strength is less evident, since the addition of fibres produces an admissible decrease (between 0 and 9% using 0.5 or 1 wt% of fibres), except in composites that use olive pruning treated with 10 wt% Na2SiO3 solution, where values remain stable, similar or better to control paste. A greater ductility of the matrix in all composites was observed. Furthermore, the alkali-activated cement matrix was bonded to olive-pruning fibre better than untreated fibre, as it is shown in SEM images. Thus, the results showed that olive-pruning fibres could be used as reinforcement in the manufacturing of alkali-activated materials when they are treated with alkali solutions.Ítem Physical, mechanical and thermal properties of metakaolin-fly ash geopolymers(Elsevier, 2022-02-16) Gómez-Casero, Miguel Ángel; de-Dios-Arana, Cristina; Bueno-Rodríguez, Juan Salvador; Pérez-Villarejo, Luis; Eliche-Quesada, DoloresDue to the large coal fly ash (FA) production and its obvious environmental impact, alternative uses of this by-product must be researched. A considerable effort is being made worldwide on research concerning the reuse of FA as a source of alternative raw materials to produce new binder materials. One of the most promising building materials are geopolymers or alkali-activated materials (AAM). In this study, FA (25–75 wt %) was used to evaluate the potential of using this waste as a source of aluminosilicates for the synthesis of geopolymers to replace metakaolin (MK) as precursor. MK and FA geopolymers were also synthesized as a control. Sodium hydroxide and sodium silicate were used as alkaline-activator mix (Na2SiO3/NaOH ratio: 0.92). The geopolymers synthesized were characterized by Fourier Transform Infrared Spectroscopy (FTIR) X-ray diffraction (XRD) and Scanning Electron Microscopy-Energy Dispersive X-ray spectroscopy (SEM-EDS). The results indicate that control geopolymers, MK and FA geopolymers have similar mechanical and thermal properties. However, the MK-FA blended geopolymers have slightly lower compressive strengths and lower thermal conductivity. The decrease in the properties of the FA and MK-FA blended geopolymers may be due to the high solid/liquid ratio used, since the spherical particles of the FA require less liquid due to their higher workability. However, the obtained geopolymers can be a satisfactory solution for the recovery of waste that results in sustainable construction materials that meet the standard to be used for loadbearing concrete masonry units with insulating properties superior to Portland cement approaching the principles of circular economy.