Browsing by Author "Vegas, Iñigo J."
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Item Effect of high-alumina ladle furnace slag as cement substitution in masonry mortars(2016-10-01) Herrero, Tamara; Vegas, Iñigo J.; Santamaría, Amaia; San-José, José T.; Skaf, Marta; GENERALLadle furnace (white or basic) slag is a significant by-product of the steelmaking industry; nowadays the manufacturing process yields two types of basic slag that are either low or high in alumina. The present research focuses mainly on the composition of the high-alumina slag and the reactivity of its compounds such as calcium aluminates, free calcium oxide, and free magnesium oxide, when aged at room temperature and at water steam temperature (accelerated aging). Additionally, a characterization was performed of pastes and masonry mortars that incorporate high alumina ladle furnace slag as a supplementary cementing material in partial substitution of Portland cement in amounts of 10% and 20% by weight. Different properties are studied such as porosity distribution, volumetric stability, mechanical strength and durability, mainly referring to wetting-drying aging cycles. The study concludes that high-alumina ladle furnace slag can induce slight hydraulic reactivity and its partial addition has no negative effect on the fundamental properties of cement masonry mortars.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 Mechanical expectations of a high performance concrete based on a polymer binder and reinforced with non-metallic rebars(2008-10) San-José, José T.; Vegas, Iñigo J.; Moisés Frías, Frías; GENERALA high performance concrete, known as polymer concrete, made up of natural aggregates and an orthophthalic polyester binder, reinforced with non-metallic bars (glass reinforced polymer) has been studied. The material is described at micro and macro level, presenting the key physical and mechanical properties using different experimental techniques. Furthermore, a full description of non-metallic bars is presented to evaluate its structural expectancies, embedded in the polymer concrete matrix. Given the closed porosity obtained in polymer concrete, its microstructure continuity and organic nature of the binder, this material is highly protected against atmospheric conditions, corrosion and chemical attacks. The present research work concludes how the structural compatibility, between polymer concrete and non-metallic bars, is obtained in the monotonic bonding tests by providing higher adherence values than traditional reinforced concrete.Item Treatment of end-of-life concrete in an innovative heating-air classification system for circular cement-based products(2020-08-01) Moreno-Juez, J.; Vegas, Iñigo J.; Gebremariam, Abraham T.; García-Cortés, V.; Di Maio, F.; TRAZABILIDAD CIRCULAR; GENERALA stronger commitment towards Green Building and circular economy, in response to environmental concerns and economic trends, is evident in modern industrial cement and concrete production processes. The critical demand for an overall reduction in the environmental impact of the construction sector can be met through the consumption of high-grade supplementary raw materials. Advanced solutions are under development in current research activities that will be capable of up-cycling larger quantities of valuable raw materials from the fine fractions of End-of-Life (EoL) concrete waste. New technology, in particular the Heating-Air classification System (HAS), simultaneously applies a combination of heating and separation processes within a fluidized bed-like chamber under controlled temperatures (±600 °C) and treatment times (25–40 s). In that process, moisture and contaminants are removed from the EoL fine concrete aggregates (0–4 mm), yielding improved fine fractions, and ultrafine recycled concrete particles (<0.125 mm), consisting mainly of hydrated cement, thereby adding value to finer EoL concrete fractions. In this study, two types of ultrafine recycled concrete (either siliceous or limestone EoL concrete waste) are treated in a pilot HAS technology for their conversion into Supplementary Cementitious Material (SCM). The physico-chemical effect of the ultrafine recycled concrete particles and their potential use as SCM in new cement-based products is assessed by employing substitutions of up to 10% of the conventional binder. The environmental viability of their use as SCM is then evaluated in a Life Cycle Assessment (LCA). The results demonstrated accelerated hydration kinetics of the mortars that incorporated these SCMs at early ages and higher mechanical strengths at all curing ages. Optimal substitutions were established at 5%. The results suggested that the overall environmental impact could be reduced by up to 5% when employing the ultrafine recycled concrete particles as SCM in circular cement-based products, reducing greenhouse gas emissions by as much as 41 kg CO2 eq./ton of cement (i.e. 80 million tons CO2 eq./year). Finally, the environmental impacts were reduced even further by running the HAS on biofuel rather than fossil fuel.