Person: Espuelas Zuazu, Sandra
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Espuelas Zuazu
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Sandra
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Ingeniería
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0000-0003-1223-515X
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811351
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Publication Open Access Experimental study of the valorization of sulfate soils for use as construction material(MDPI, 2022) Seco Meneses, Andrés; Del Castillo García, Jesús María; Perlot, Céline; Marcelino Sádaba, Sara; Prieto Cobo, Eduardo; Espuelas Zuazu, Sandra; Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería; Universidad Pública de Navarra / Nafarroako Unibertsitate PublikoaThis article shows an experimental investigation carried out for the stabilization of a sulfate soil. The stabilization was carried out in two phases: the first phase was the consumption of the sulfate present in the soil through its controlled transformation into ettringite. After this, a modified soil with lower maximum density, greater optimum moisture identified via standard proctor (SP) test, no plasticity and improved unconfined compressive strength (UCS) was obtained. In the second phase, the modified soil was stabilized by the use of different additives rich in oxides of calcium or magnesium, combined with by-products or waste materials containing reactive aluminum or silicon oxides. As a result, the mechanical strength of the modified soil was improved. In this phase, a binary binder composed of a magnesium oxide product and ground granulated blast-furnace slags (GGBS) obtained the highest UCS. The binary binder composed of lime and an alumina filler formed ettringite in the treated soil. This experiment allowed for the validation of a two-phase stabilization process and the non-conventional additives used, mainly magnesium oxide and GGBS, even for high-bearing-requirement pavement layers’ construction.Publication Open Access Stabilization of a clay soil using cementing material from spent refractories and ground-granulated blast furnace slag(MDPI, 2021) Seco Meneses, Andrés; Del Castillo García, Jesús María; Espuelas Zuazu, Sandra; Marcelino Sádaba, Sara; García Gracianteparaluceta, Beñat; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISCNowadays, huge amounts of refractory materials are generated around the world. The majority of them lack valorization methods. This study analyzes the ability of a doloma and two magnesia spent refractory wastes as soil stabilizers on their own, as well as when combined with Ground-Granulated Blast Furnace Slags (GGBS). These materials showed a limited ability for the soil’s plasticity modification from a plasticity index of 15.6 to a minimum of 12.7. The high pH of the additives increased the soil’s pH from 7.88 to values in the range of 10.94–11.25 before the 28 days, allowing the development of the pozzolanic reactions. Unconfined compressive strength (UCS) increased along the curing time, reaching a maximum value of 5.68 MPa after 90 days. Based on the UCS, the optimum refractory GGBS ratios oscillate between 30:70 and 50:50. The UCS values after soaking samples reduced the unsoaked results between 68.70% to 94.41%. The binders considered showed a low effect against the soil swelling and the lack of delayed expansive effects because of the MgO hydration. Finally, X Ray Diffraction (XRD) tests showed that the stabilization only slightly modified the combinations of mineralogy and the formation of Magnesium Silicate Hydrate (MSH) gels.Publication Open Access Sulphate soil stabilisation with magnesium binders for road subgrade construction(Taylor and Francis, 2020) Seco Meneses, Andrés; Espuelas Zuazu, Sandra; Marcelino Sádaba, Sara; García, Beñat; Del Castillo García, Jesús María; Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería; Gobierno de Navarra / Nafarroako GobernuaThis paper analyzes the ability of magnesium oxide-based additives to stabilise a low bearing gypsum marly soil, in order to reach subgrade requirements. This soil was not adequate for stabilisation with lime or cement because of its high sulphate content. Binders considered in this investigation were composed of three reactive Mg products and by products, both with and without ground granulated blast furnace slags (GGBS). They were compared to two cements and an aerial lime as soil stabilisers in a laboratory investigation and a field trial. Laboratory tests showed that Mg products with GGBS reached strength results close and at times even better than those of cement. One of the Mg products was the only additive able to reduce the natural soil swelling. Leaching tests demonstrated the ability of the Mg products to reduce the soil leaching of substances like calcium, magnesium, sulphate and chloride. In field trials two of the Mg products combined with GGBS met the bearing capacity requirements for subgrades, in accordance with the Spanish standard.Publication Open Access Recycled granulates manufacturing from spent refractory wastes and magnesium based binder(Elsevier, 2023) Seco Meneses, Andrés; Del Castillo García, Jesús María; Perlot, Céline; Marcelino Sádaba, Sara; Espuelas Zuazu, Sandra; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISCThis paper analyzes the ability of two Spent Refractory Wastes (SRW) for the manufacturing of recycled granulates for construction applications. A binary magnesium oxide and ground granulated blast furnace slag hydraulic binder was considered as an agglomerating agent for the granulates manufacturing. Influence of curing atmosphere was carried out: in air, 20 % CO2 and 100 % CO2 atmosphere up to 28 days. Granulometry, thermal analysis, particle density, bulk density, water absorption and mechanical strength tests were performed to characterize the granulates. SRW showed their ability for the granulates manufacturing. Results demonstrated the existence of a residual reactivity of the wastes considered. A direct relationship between the CO2 content of the curing atmosphere and the granulates hydration degree was observed. Carbonation process increased from 7 days to 28 days and direct relationships were observed between the CO2 content and the carbonation degree as well as between the binder dosage and the carbonation degree. CO2 curing reduced the water absorption and increased the compressive strength of the granulates.Publication Open Access Assessment of the ability of MGO based binary binders for the substitution of Portland cement for mortars manufacturing(Elsevier, 2022) Seco Meneses, Andrés; Espuelas Zuazu, Sandra; Marcelino Sádaba, Sara; Echeverria Lazcano, Angel María; Del Castillo García, Jesús María; Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería; Gobierno de Navarra / Nafarroako GobernuaThis article evaluates the ability of a magnesia kiln dust (PC-8) and a commercial calcined MgO (MCB100), combined with ground granulated blastfurnace slag (GGBS), as constituents of binary M-S-H binders. Mortars and pastes were manufactured and their properties were compared to those of Portland Cement (PC). MgO-based mortars showed an increase in setting time and higher fresh consistency. At earlier ages MgO mortars showed lower mechanical properties. At 90 days both MgO-based mortars overcame the PC flexural strength and PC-8 + GGBS also overcame its compressive strength. X-Ray Diffraction and Thermogravimetry tests demonstrated the presence of M-S-H in the pastes.Publication Open Access Valorization of insulation cellulose waste as solid biomass fuel(MDPI, 2021) Espuelas Zuazu, Sandra; Marcelino Sádaba, Sara; García, Beñat; Seco Meneses, Andrés; Del Castillo García, Jesús María; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación; Gobierno de Navarra / Nafarroako GobernuaThis paper investigates the ability of insulation cellulose fiber powder (CFP) to be pelletized for its valorization as biomass fuel. CFP is a waste originating from insulation cellulose manufacturing that lacks any method of valorization because of its boron salts content. A sugar byproduct and lignosulfonate (LS) were considered as binders for the pellet manufacturing process. Physical tests were carried out to characterize the pellets’ performance. Chemical and combustion tests were considered to state the pellets’ potential as a green energy source. Raw CFP showed good ability in its pelletization and durability in the range of 15–30% of moisture content. The pellet’s density decreased as water content increased. Binders increased the pellet’s length before and after the durability test. Binders also increased the CFP pellet’s water absorption, demonstrating a potential decrease in durability against environmental factors. Binders also decreased the lower heating value. Ultimate analysis showed a slight Nitrogen increase in both binder combinations that could potentially raise the pollutant NOx combustion emissions. All the combinations showed adequate combustion characteristics, but binders increased ash production. Additives decreased the CFP volatile matter content and increased the fixed carbon, which could facilitate a more stable combustion. DTA curves showed a mass loss rate decrease in the volatile stage for the binder combinations, which also could be considered as an indicator of a more stable combustion. The ashes’ chemical compositions when analyzed by XPS showed boron contents oscillating between 10.03% and 16.42%, demonstrating the possibility of recovering them from the combustion ashes.