Browsing by Author "Frías, M."
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Item Aging and durability of ternary cements containing fly ash and activated paper sludge(2014-02-15) Vegas, I.; Gaitero, J. J.; Urreta, J.; García, R.; Frías, M.; GENERAL; Tecnalia Research & Innovation; ECOEFICIENCIA DE PRODUCTOS DE CONSTRUCCIÓN; Infraestructuras y Servicios CorporativosThis research work deals with durability aspects of ternary cements containing 79 wt.% ordinary Portland cement (CEM I), 10.5 wt.% coal fly ash and 10.5 wt.% thermally activated paper sludge. Aging tests were performed to study the resistance of the new ternary cement matrixes to the following aggressive exposure conditions: accelerated freeze/thaw cycles, marine environment and Spanish plateau climate conditions. Ternary cements revealed a high resistance to accelerated freeze/thaw cycles. In addition, after 18 months of exposure, they exhibited enhanced performance under marine conditions and similar resistance to Spanish plateau's climate, compared to ordinary Portland cement.Item The combined effect of activated paper sludge and fly ash on the ternary cement properties(European Conference on Composite Materials, ECCM, 2012) Frías, M.; Vegas, I.; Goñi, S.; García, R.; Vigil De La Villa, R.; GENERALThis paper presents the main scientific and technical aspects of a pozzolans blend (activated paper sludge (APS) and fly ash (FA)) and its influence on the ternary cement behaviour. Due to the high pozzolanic activity of binary addition, the blended cements (6 and 21%) shows a different behaviour with respect to the control one. The normal consistency water content (up to 10%) and the initial setting decrease in comparison with the control paste. Finally, the compressive strength slightly decreased in the blended cements elaborated with 21% of the pozzolan blend, although the decrease in their strength is lower than the total percentage of cement that is replaced. At 90 days, a recovery of mechanical resistance is observed in the ternary cements as a consequence of the activity developed by the fly ash.Item Conversion and re-use of paper sludge in a pozzolanic material for the construction(2005) Frías, M.; De Rojas, M. I.Sánchez; Urreta, J.; Vegas, I.; San José, J. T.; García, R.; Vigil, R.; Gaballah, I.; Mishra, B.; Solozabal, R.; Tanaka, M.; Infraestructuras y Servicios Corporativos; GENERALThis paper describes the approach and objectives of the research project as well as the results obtained in the initial phases. The starting waste used for this research is a Spanish paper sludge coming from a paper industry which uses 100% of recycled paper as raw material. The first results show that the calcining temperature and stay in furnace play an important role on the pozzolanic activity of the calcined product and in its reaction kinetics. Calcining temperatures of 700°C and 2 hours of stay were the fixed conditions in order to get the best pozzolanic properties for this calcined sludge.Item Decalcification of activated paper sludge - Fly ash-Portland cement blended pastes in pure water(2013-07) Goñi, S.; Frías, M.; De La Villa, R. Vigil; Vegas, I.; GENERALDecalcification in pure water of ternary Portland cement (TPC) pastes, containing thermally activated paper sludge and fly ash, has been evaluated from the leaching of Ca2+ in pure water at the temperature of 20 C during 90 days. Monitoring of calcium loss showed that the leaching kinetics are controlled by diffusion. The degradation of the material over time is estimated from the calcium effective diffusivity. A similar study of plain ordinary Portland cement (OPC) pastes was carried out for comparison. The results showed lower effective diffusion coefficients of calcium in the case of the TPC pastes. This behaviour is related to its microstructure, which is denser than that of OPC as a result of the pozzolanic activity of both additions.Item Design and performance of masonry mortars made with recycled concrete aggregates(2009) Vegas, I.; Azkarate, I.; Juarrero, A.; Frías, M.; GENERALThe present paper discusses the technical feasibility of using the fine fraction of recycled aggregate from concrete rubble to manufacture cement mortar and possible conditions. An initial study of the chemical and physical-mechanical characteristics of fines recycled from selected concrete showed that their high absorptivity and high sulfate content compared to natural limestone sands were the limiting factors to their in masonry mortars. As in the case of structural concrete, a blend of recycled and natural aggregate would appear to be suitable for masonry mortars. A study of the mix proportions and characteristics of mortars made with recycled concrete aggregate showed that up to 25% recycled aggregate can be used in cement-based masonry mortars with no significant decline in performance and no new admixtures or higher cement content requires.Item The deterioration and environmental impact of binary cements containing thermally activated coal mining waste due to calcium leaching(2018-05-10) Arribas, I.; Vegas, I.; García, V.; Vigil de la Villa, R.; Martínez-Ramírez, S.; Frías, M.; TRAZABILIDAD CIRCULAR; GENERALCalcium-leaching processes can potentially degrade the structure of a concrete matrix. This problem is studied here through the progressive dissolution of Ca2+ in both ordinary Portland cement pastes (C-0) and binary cement blends (C-20) containing 20% thermally Activated Coal Mining Waste (ACMW).1 A series of accelerated tests are conducted that involve the immersion of these cement pastes in a 6 M ammonium nitrate solution at a temperature of 20 C for 7 and for 21 days. A rise in paste porosity was observed, due to increased capillary pore sizes of between 5 and 0.1 μm. In the case of the 20% ACMW pastes (C-20), calcium leaching decreased, probably as a consequence of the pozzolanic effect of the ACMW, while potassium and magnesium leaching increased, due to the presence of the phyllosilicates in the ACMW. The paste compounds most affected by leaching were Ca(OH)2, C6AS3H32, and C4AC¯H12. In general terms, it can be concluded that the incorporation of ACMW into binary cements slightly reduces the calcium leaching phenomena. Concerning the environmental impact assessment, the substitution of 20% OPC by ACMW reduced CO2 emissions by as much as 12% and improved energy efficiency by using approximately 19% fewer fossil resources.Item Evolution of mineralogical phases produced during the pozzolanic reaction of different metakaolinite by-products: Influence of the activation process(2012-02) Frías, M.; Vigil, R.; García, R.; Rodríguez, O.; Goñi, S.; Vegas, I.; GENERALIn the past, different investigations have focused on waste containing kaolinite as an alternative source for recycled metakaolinite. However, it is well known that the activation conditions play an important role in the characteristics of the final product. This research presents an exhaustive study about the evolution of the mineralogical phases during the pozzolanic reaction of two metakaolinite by-products obtained from different activation processes: activation of paper sludge at lab scale (700 °C and 2. h) and at industrial scale (720-740 °C and 20-30. min) with a fluidized bed combustion system.It is shown that both metakaolinite by-products exhibit a different pozzolanic behavior, suggesting a direct influence on the subsequent performance of new blended cement matrices. The metakaolinite by-product obtained at lab-scale (MWL), generates an additional phase (carbonate/metakaolinite type structures) as predominant crystalline phase in the pozzolan/Ca(OH) 2 system up to 28days of reaction. Stratlingite (C 2ASH 8) also appeared as minor stable phase after 7days of reaction. On the other hand, the metakaolinite by-product from industrial process (MWI) favors the formation of C 4AC̄H 12 phase, whereas stratlingite was not identified.Item Freeze-thaw resistance of blended cements containing calcined paper sludge(2009-08) Vegas, I.; Urreta, J.; Frías, M.; García, R.; GENERAL; Infraestructuras y Servicios CorporativosThis work deals with the frost resistance of blended cements containing calcined paper sludge (source for metakaolin) as partial Portland cement replacements. Freeze-thaw tests were performed on blended cement mortars containing 0%, 10% and 20% waste paper sludge calcined at 650 °C for 2 h. Cement mortar specimens were exposed to freezing and thawing cycles until the relative dynamic modulus of elasticity fell below 60%. The performance of the cement mortars was assessed from measurements of weight, ultrasonic pulse velocity, compressive strength, mercury intrusion porosimetry and SEM. Failure of the control cement mortar occurred before 40 freeze/thaw cycles, while cement mortar containing 20% calcined paper sludge failed after 100 cycles. After 28 and 62 freezing and thawing cycles, cement blended with 10% and 20% calcined paper sludge exhibited a smaller reduction in compressive strength than the control cement.Item Ion Mobilisation and Transport Through Cement Mortars Blended With Thermally Activated Paper Sludge in Natural Climatic Conditions(2009) García Giménez, R.; Vegas, I.; Vigil de la Villa, R.; Frías, M.; GENERALOne of the problems to affect Portland cement matrices is low resistance to aggressive agents, due principally to the presence of a high content of portlandite in the hydrated cements. Pozzolanic materials have, for decades, played an important role in improving the durability of cement-based materials. This work studies the behaviour of cement mortar matrices blended with 10% calcined paper sludge (source for metakaolin, MK) and exposed to different environmental conditions (marine and tableland environments). The results obtained using X-ray diffraction and scanning electron microscopy/energy-dispersive X-ray analyser techniques show that the ions present speed of different penetration as well as various phases and/compounds in the matrices following exposure over 1 year.Item Obtención de una adición puzolánica a partir de la calcinación controlada de lodos de destintado de papel: Estudio de prestaciones en matrices de cemento(2006-07) Vegas, I.; Frías, M.; Urreta, J.; San José, J. T.; GENERAL; Infraestructuras y Servicios CorporativosMineralogically, the paper mill sludge consists essentially of calcite, kaolinite, talc and other philosilicates (illite, chlorite). When such sludge is subjected to controlled thermal treatment, its kaolinite component may be transformed into metakaolin, yielding a product with high pozzolanic reactivity. This study was designed to analyze a number of scientific questions around the production of pozzolanic additions via controlled thermal activation of paper mill sludge and to evaluate the performance of such additions when included in a cement matrix. The findings show that paper mill waste activation is optimal when the sludge is calcined for 2 hours at 700°C in the 700-800°C intervale. A comparative study between the cement made with the new addition and a commercial cement (CEM I-42.5R) used as a reference led to highlight the scientific and technical viability of this waste as a cementing seconding material.Item The pozzolanic properties of paper sludge waste(2008-07) García, R.; Vigil de la Villa, R.; Vegas, I.; Frías, M.; Sánchez de Rojas, M. I.; GENERALThe use of paper de-inking sludge in pozzolanic material manufacture permits a disposable residue to be included in the cycle of the materials. A study on the reuse of paper de-inking sludge, undertaken in Spain, shows its potential as raw material for yielding a product with pozzolanic activity. This study establishes that an optimal condition for transforming paper de-inking sludge into a pozzolanic addition is achieved at 700 °C maintained for 2 h. Under these conditions, the organic matter disappears and the calcined sludge becomes active by transforming kaolinite into metakaolinite. The calcined product exhibits high pozzolanic activity. The present paper also analyses mechanical, physical and chemical properties of a blended cement containing 90% (in mass) standard Portland cement (CEM I-52,5N) and 10% of the pozzolanic addition obtained from controlled calcination of paper de-inking sludge (for 2 h at 700 °C). When the blended cement is compared with a cement containing 100% standard Portland cement, the following conclusions can be mentioned: a significant gain in compressive strength from 7 days on, a sooner initial setting time, as well as a reduction in SO3 percentage. In any case, the new blended cement complies with requirements set out in Spanish/European standard UNE EN 197-1-Part 1.Item Pre-normative research on the use of mixed recycled aggregates in unbound road sections(2011-05) Vegas, I.; Ibañez, J. A.; Lisbona, A.; Sáez De Cortazar, A.; Frías, M.; GENERAL; TRAZABILIDAD CIRCULAR; Tecnalia Research & InnovationThis paper presents and discusses the results arising from a pre-normative study aimed at determining the physical, chemical and mineralogical characteristics of mixed recycled aggregates produced from the treatment of mixed rubble for use in unbound structural layers of road. The results of this research show that the combined presence of concrete and ceramic materials induces pozzolanic reactions, which contribute to an increase in the bearing capacity of the compacted mixed recycled aggregate. From an analysis of their chemical characteristics, it can be inferred that the total sulphur compound content, the gypsum content and soluble salt contents can be regulated with reference to the water soluble sulphates test, given the high correlation that exists between those parameters. Generally, mixed recycled aggregates with ceramic material contents below 35%, organic matter contents below 0.8% and water soluble sulphate contents below 0.4% constitute a granular material that is technically feasible for use in unbound structural road sections.Item Reuse of waste paper sludge as supplementary cementing material(Minerals, Metals and Materials Society, 2008) Frías, M.; Rodríguez, O.; De Rojas, M. I.Sánchez; Nebreda, B.; Vegas, I.; Urreta, J.; García, R.; Vigil, R.; GENERAL; Infraestructuras y Servicios CorporativosThis paper shows the possibility of reutilize paper sludge waste as supplementary cementing material for the cement manufacture. This industrial waste consists essentially of a mixture of organic matter (30%) and inorganic compound, such as calcite and clay minerals. The raw paper sludge does not present pozzolanic properties, but once calcined at 650°C during 2 hours, exhibits high pozzolanic activity, similar to silica fume at 28 days, as a consequence of the transformation of kaolinite into metakaolinite. Calcined paper sludge was used as partial Portland cement replacements of 0, 5, 10 and 20%. Enhancement in compressive strength was appreciably obtained for 10 and 20% substitution levels from 7 days on. Furthermore, calcined paper sludge slightly reduces the initial and final setting times of cement paste.Item Steel slag aggregate in concrete: The effect of ageing on potentially expansive compounds(2010) Frías, M.; San-José, J. T.; Vegas, I.; GENERALGrowing numbers of plants have sprung up in recent years to treat the electric arc furnace slag generated in scrap metal melting. When this by-product is separated, crushed and screened, it yields a granular material known as steel slag aggregate, which may be profitably used in the manufacture of commercial concrete. The feasibility of this application depends essentially on the volume stability of the resulting aggregate. The present paper discusses the potentially expansive compounds (Cl-, SO3, free CaO and free MgO) present in aggregate derived from different types of black slag during aggregate ageing. The aim is to establish optimal ageing conditions to ensure volume stability in steel slag aggregate. The findings showed that the slag analyzed had low concentrations of the expansive compounds studied and that possible swelling can be reduced by 45-day ageing.Item Use of coal mining waste as pozzolanic material in new blended cement matrixes(European Conference on Composite Materials, ECCM, 2014) Vigil De La Villa, R.; García, R.; Ramírez, M.; Rubio, V.; Frías, M.; Rodríguez, O.; Lahoz, E.; Martínez-Ramirez, S.; Fernández-Carrasco, L.; Vegas, I.; GENERALResearch and eco-innovation geared to obtain alternative sources of raw materials from waste constitute pathways for enhancing the competitiveness of resource-intensive industries. Cement and concrete manufacture calls for new sources of new, highly pozzolanic products to improve the mechanical properties and durability of the resulting matrices, while at the same time reducing production costs and environmental impact. Spanish coal mining wastes generated in the extraction and washing steps from a mine in the Castilla-León region were investigated. Mineralogically, these wastes are composed by kaolinite (20-30%), illite (45-70%) and quartz (5-15). This composition is very interesting in order to activate, by controlled thermal activation, the present kaolinite that generates metakaolin, a highly pozzolanic product. Morphological, textural and microstructural changes affect the activity and reactivity of activated wastes. These first studies open up a new research line, practically unknown to the international research community, and stand out the important economic and environmental benefits associated with the recycling of these wastes as supplementary cementing materials for future commercial blended cements.