Departamento de Ingeniería Química, Ambiental y de los Materiales
URI permanente para esta comunidadhttps://hdl.handle.net/10953/42
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Examinando Departamento de Ingeniería Química, Ambiental y de los Materiales por Materia "Alkali activated cements"
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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 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.