Browsing by Author "Vigil de la Villa, R."
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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 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 Laboratory-scale study and semi-industrial validation of viability of inorganic CDW fine fractions as SCMs in blended cements(2021-02-15) Moreno-Juez, J.; Vegas, Iñigo J.; Frías Rojas, M.; Vigil de la Villa, R.; Guede-Vázquez, E.; TRAZABILIDAD CIRCULAR; GENERALThe construction industry and more particularly cement manufacture industry are European Green Deal strategic priorities for the circularity of Europe’s construction and demolition waste (CDW) stream with a view to reducing CO2 emissions. The industry is engaged in a number of strategies to that end, one of which is to manufacture new low-carbon, lower clinker/cement ratio cements by replacing portland clinker with inorganic fractions of CDW featuring hydraulic or pozzolanic properties. Against the backdrop of that global challenge, the present study explores the cementitious potential of the limestone and siliceous concrete fines and shatterproof building glass found in CDW as supplementary cementitious materials (SCMs) in new blended cements. The research was conducted in two stages: generation of new laboratory-scale knowledge; and industrial validation of the viability of using the highest volume waste streams. The laboratory-scale findings revealed that the presence of the filler effect and pozzolanicity in micronised inorganic fractions of concrete and building glass waste induces the neoformation of hydrated phases and C-S-H gel. Those two developments improve the short- and long-term physical and mechanical properties of the new blended cements at optimal replacement ratios of 5–7%. The order of material effectiveness in shortening setting times, increasing the heat of hydration and maintaining mechanical strength was observed to be as follows: limestone concrete > siliceous concrete > glass waste. Laboratory analysis was followed by a pilot study consisting in the manufacture of 184 t of blended cement in which 5% of the clinker was replaced by recycled concrete. Higher product performance than the commercial reference cement confirmed the industrial, technical, economic and environmental viability of the new product, estimated to hold potential for CO2 emissions abatement on the order of 41 kg CO2 eq./t of cement, which could translate into 80 Mt CO2 eq./year worldwide.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.