Examinando por Autor "Eliche-Quesada, Dolores"
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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 Alkaline activated cements obtained from ferrous and non-ferrous slags. Electric arc furnace slag, ladle furnace slag, copper slag and silico-manganese slag(Elsevier, 2024-03) Gómez-Casero , Miguel Ángel; Bueno, Salvador; Castro-Galiano, Eulogio; Eliche-Quesada, DoloresFerrous slag: electric arc furnace slag (EAFS) and ladle furnace slag (LFS); and non-ferrous slag: copper slag (CS) and silicon-manganese slag (SiMnS) have been used as precursors for alkali activated cements (AACs). The objective of the study was to evaluate the effect of the silica modulus (Ms = SiO2/K2O) (0.5–1.8) of the potassium silicate/potassium hydroxide solution on the microstructure and technological properties of AACs using individual slags. The results obtained indicate that under the activation conditions used, CS and EAFS are more reactive slags, giving rise to AACs with optimum flexural and compressive strengths of 7.5 and 51.5 MPa and 5.7 and 30.5 MPa for a Ms = 1.4, respectively. While the SiMnS and LFS are less reactive resulting in AACs with flexural and compressive strengths of 3.2 and 11.6 MPa at Ms = 1.4 for SiMnS and 1.1 MPa and 4.6 MPa at Ms = 0.9 for LFS. In all AACs, the development of the alkaline activation reaction is confirmed due to the presence of gel, of different nature and quantity depending on the precursor used. The lower mechanical properties of the AACs using SiMnS and LFS as precursor may also be due to the presence of microcracks. Therefore, this study confirms that ferrous and non-ferrous slags can be used as precursors of AACs, with the type of precursor and the modulus of the activating solution influencing mechanical properties. AACs using CS and EAFS can be used in structural applications, while those using SiMnS and LFS can be used in non-structural applications in civil engineering.Ítem Alkaline-activated cements synthesized from spent diatomaceous earth and different industrial sludge ashes(Taylor & Francis, 2025-07-29) Felipe-Sesé, Manuel; García-Díaz , Almudena; Gómez-Casero, Miguel Ángel; Eliche-Quesada, DoloresThis study evaluates the technological properties of alkali-activated cements (AACs) produced from spent diatomaceous earth (SDE), a by-product of beer filtration, combined with 20wt.% of industrial sludge ashes. The ashes used include brewery sludge ash (BSA), oil industry sludge ash (OSA), pulp–paper sludge ash (PSA), and aluminum anodizing sludge ash (AASA). Activation was carried out using a 1:1 mixture of sodium silicate and sodium hydroxide, with curing at room temperature for 7 and 28 days. Microstructural analysis was performed using X-ray diffractometer (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). The results show that the chemical composition of the sludge ashes significantly influences the mechanical performance of AACs. Calcium-rich wastes improved compressive strength, while the presence of SO3 and P2O5 reduced it due to the formation of expansive phases or secondary reactions. The best results were achieved with BSA-SDE cements, which reached compressive and flexural strengths of 30.0 and 6.5MPa, respectively.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 Geopolymers made from metakaolin sources, partially replaced by Spanish clays and biomass bottom ash(Elsevier, 2021-08) Eliche-Quesada, Dolores; Calero-Rodríguez, Alexis; Bonet-Martínez, Eduardo; Pérez-Villarejo, Luis; Sánchez-Soto, Pedro JoséThe main objective of this investigation is to study the effect of the substitution of metakaolin (MK) (from calcined industrial kaolin) by four different calcined natural Southern Spain clays traditionally used in the brick and tile sector, as well as by the biomass bottom ash residue (BBA) from the combustion of a mix of olive and pine pruning on the synthesis of geopolymer with physical, mechanical and thermal properties comparable to those of classic construction materials. As alkaline activator, a 8 M solution of sodium hydroxide and sodium silicate have been used. Raw materials, metakaolin; Spanish clays: black clay (BC), yellow clay (YC), white clay (WC), red clay (RC) and BBA were characterized by chemical analysis (XRF), mineralogical analysis (XRD), and particle size analysis. Control geopolymers containing only metakaolin, and batch of geopolymers were formulated containing equal proportions of metakaolin, BBA and each of the four types of clay. After the curing period, at 60 °C for 1 day geopolymers were demolded and stored 27 days at room temperature. Geopolymers were characterized using Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy (SEM-EDS), XRD and Attenuated Total Reflectance- Fourier Transform Infrared Spectroscopy (ATR-FTIR). Their physical, mechanical and thermal properties have also been studied. The addition of BBA and different types of calcined clays to metakaolin gives rise to geopolymers with higher mechanical properties increasing the compressive strength of the control geopolymer containing only MK (24.9 MPa) by more than 50% for the GMK-BBA-WC geopolymers (38.5 MPa). The clays act as fillers and/or promote the precipitation of calcium-rich phases (Ca)-A-S-H-G gel that coexists with the (Na)-A-S-H gel type. The relevant results of physical, mechanical and thermal properties obtained in this research demonstrate the potential of Spanish clays and BBA as binders and substitutes for metakaolin.Ítem Investigation of waste clay brick (chamotte) addition and activator modulus in the properties of alkaline activation cements based on construction and demolition waste(Elsevier, 2024-05-01) García-Díaz, Almudena; Delgado-Plana, Pedro; Bueno, Salvador; Eliche-Quesada, DoloresThe use of construction and demolition waste (CDW) as a raw material for the manufacture of alkali-activated cements (AACs) is a promising and sustainable way to recover construction waste. CDW mainly consists of mineral residues such as concrete and ceramic waste. In this study, CDW with a high fraction of concrete waste is used, so the enrichment effect of the waste in the ceramic fraction is studied. For this purpose, different proportions of chamotte (CHM) have been incorporated (0–40 wt%). The CDW precursor or CDW-CHM precursors have been activated using 8 M sodium hydroxide and sodium silicate solution, using an activator modulus (mol SiO2/mol Na2O = Ms = 1.0) and the specimens were cured at room temperature. The liquid/binder ratio was 0.45 for all the pastes manufactured. The results indicate that the progressive enrichment of the ceramic fraction or the incorporation of CHM results in alkaline activated cements (AACs) with similar physical properties such as bulk density, water absorption and total porosity, but with improved mechanical properties. The incorporation of 40 wt% CHM results in optimum compressive strengths with values of 29.7 and 41.2 MPa after 28 and 56 days of curing respectively, higher than those obtained for the control specimens containing only CDW 15.2 MPa and 30.65 MPa respectively. Subsequently, the impact of the silicate modulus of the alkaline activator (Ms = 0.5; 1.0 and 2.0) on the performance of the AACs was evaluated in the control cement and in the optimum cement incorporating 40 wt% CHM. The mechanical performance of the AACs improves substantially with increasing activator modulus up to a certain threshold Ms = 1.0, but finally decreases slightly with Ms = 2.0. Therefore, this study demonstrates the possibility of valorising wastes from the construction sector through their use as precursors in the manufacture of environmentally friendly alkaline activated cements with macroscopic performances that improve with the content of the ceramic fraction (CHM).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.Ítem Synthesis and characterization of alkali-activated materials containing biomass fly ash and metakaolin: effect of the soluble salt content of the residue(Springernature, 2022-05-07) Jurado-Contreras, Sofía; Bonet-Martínez, Eduardo; Sánchez-Soto, Pedro José; Gencel, Osman; Eliche-Quesada, DoloresThe present study investigates the production and characterization of alkali-activated bricks prepared with mixing metakaolin (MK) and biomass fly ash from the combustion of a mix of pine pruning, forest residues and energy crops (BFA). To use this low cost and high availability waste, different specimens were prepared by mixing MK with different proportions of BFA (25, 50 and 75 wt%). Specimens containing only metakaolin and biomass fly ash were produced for the purpose of comparison. Effects of the alkali content of biomass fly ash, after a washing pretreatment (WBFA), as well as the concentration of NaOH solution on the physical, mechanical and microstructural properties of the alkali-activated bricks were studied. It was observed that up to 50 wt% addition of the residue increases compressive strength of alkali-activated bricks. Alkalinity and soluble salts in fly ash have a positive effect, leading materials with the improved mechanical properties. Concentration of NaOH 8 M or higher is required to obtain optimum mechanical properties. The compressive strength increases from 23.0 MPa for the control bricks to 44.0 and 37.2 MPa with the addition of 50 wt% BFA and WBFA, respectively, indicating an increase of more than 60%. Therefore, the use of biomass fly ash provides additional alkali (K) sources that could improve the dissolution of MK resulting in high polycondensation. However, to obtain optimum mechanical properties, the amount of BFA cannot be above 50 wt%.