Examinando por Autor "Eliche-Quesada, Dolores"
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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 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 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%.