High performance self-compacting concrete with electric arc furnace slag aggregate and cupola slag powder

The development of self-compacting concretes with electric arc furnace slags is a novelty in the field of materials and the production of high-performance concretes with these characteristics is a further achievement. To obtain these high-strength, low-permeability concretes, steel slag aggregates and cupola slag powder are used. To prove the effectiveness of these concretes, they are compared with control concretes that use diabase aggregates, fly ash, and limestone supplementary cementitious materials (SCMs, also called fillers) and intermediate mix proportions. The high density SCMs give the fresh concrete self-compacting thixotropy using high-density aggregates with no segregation. Moreover, the temporal evolution of the mechanical properties of mortars and concretes shows pozzolanic reactions for the cupola slag. The fulfillment of the demands in terms of stability, flowability, and mechanical properties required for this type of concrete, and the savings of natural resources derived from the valorization of waste, make these sustainable concretes a viable option for countless applications in civil engineerin

Durability of high-performance self-compacted concrete using electric arc furnace slag aggregate and cupola slag powder

The current trend in the development of self-compacting concrete with sustainable construction materials has served as a guide to design a novel self-compacting concrete, with siderurgical by-products (steel slag aggregates and cupola slag powder as supplementary cementing material) that also meets the demands of high-performance concrete. This research sets out to clarify the unknown behavior of slag concrete, its durability, which is the ability to withstand any process that tends to deteriorate it. In order to assess the durability of this eco-friendly concrete, three control mixes were manufactured with the same high-quality coarse aggregate (diabase) and three different fines, limestone filler, fly ash and cupola slag powder. All the mixtures were subjected to the same tests, the results demonstrate that steel slag concrete shows an excellent response against carbonation, a slightly lower response against thermal shock cycles, similar drying shrinkage and a superior response against the action of freezing-thawing cycles and abrasion wear in comparison to the control mixes

Physical-Mechanical Properties of Cupola Slag Cement Paste

ABSTRACT: The high consumption of natural resources in the industrial sector makes it necessary to implement measures that enable the reuse of the waste generated, seeking to achieve circular economy. This work assesses the viability of an alternative to the use of CEM III B 32.5 R cement in mortars for the internal coating of centrifugally spun cast iron pipes for water piping. The proposal is to reuse the slag generated in the casting process after being finely ground, as an addition mixed with CEM I 52.5 R cement, which is basically Portland clinker. In order to analyse this possibility, an extensive experimental campaign was carried out, including the analysis of the cupola slag (micro-structural and chemical composition, leachates, setting time, vitrification, puzzolanicity and resistance to sulphate) and regarding the mortars (workability and mechanical properties). The experimental programme has shown that the optimum substitution is achieved with a replacement percentage of 20% of the cement, with which similar workability, superior mechanical properties and guaranteed resistance to sulphate attack are obtained. In addition, both economic and environmental savings are achieved by not having to transport or landfill the waste. In addition, the new cement is cheaper than the cement currently used

Viability of Cupola Slag as an Alternative Eco-Binder and Filler in Concrete and Mortars

ABSTRACT: Obtaining new materials capable of meeting society?s demands motivates the search for new solutions that are capable of satisfying twofold requirements: respect for the environment and obtaining more durable and resistant materials. Cupola slag is a by-product generated in the process of obtaining ductile iron. When the slag undergoes rapid cooling, its vitrification is favored, leaving the silica in an amorphous structure and, thus, susceptible to reacting. Through reaction, the slag can develop cementing properties and cement can consequently be partially replaced with residue, providing savings in economic and environmental costs compared to traditional hydraulic binders. In this study, the physical and chemical properties of cupola slag and its recovery process are analyzed. Mortars that incorporate traditional admixtures (fly ash and limestone filler) have been manufactured and consistency and mechanical properties have been compared with mortars that incorporate cupola slag admixture. Mortars have also been manufactured with normalized sand and with Portland cement replacements (0, 10, 20, and 30% by weight) with cupola slag, and both the consistency and the mechanical properties have been compared at 7, 28, 60, and 90 days. The results obtained show the suitability of cupola slag as a binder and as an admixture, with respect to the traditional ones, and how the mechanical properties tend to converge for all of the replacement levels characterized, for ages close to 90 days of age

Análisis del comportamiento a fatiga de morteros con árido reciclado procedentes de vía mediante tomografía axial computarizada

Para la mejora de la calidad de las infraestructuras ferroviarias y la reducción de los costes de mantenimiento se plantea la sustitución de la vía tradicional por vía en placa. Debido al gran coste que supone esta nueva sustitución se plantea el empleo de árido reciclado proveniente de componentes ferroviarios fuera de uso, concretamente de las traviesas y el balasto. En una primera etapa, se analizará el comportamiento a fatiga de morteros fabricados con las arenas recicladas tanto de las traviesas como del balasto. Para ello se han fabricado probetas cilíndricas miniatura de 40 mm de altura y 20 mm de diámetro para las que se han empleado tres arenas de diferentes procedencias, pero con la misma granulometría: arena de traviesa, de balasto y de sílice normalizada. El método empleado para la caracterización en fatiga es el método acelerado de LOCATI. Para la evaluación del daño ocasionado por la fatiga se ha utilizado la técnica de Tomografía Axial Computarizada que permitirá entre cada bloque de fatiga aplicado evaluar la evolución del tamaño y forma de los poros de mayor tamaño, numero de poros, así como detectar la aparición de fisuras y la evolución de las mismas.Nowadays railway infrastructure is becoming obsolete, due to evolution of the trains. For this reason, it is fundamental to improve railroad superstructures, as well as to find a way to recycle the superstructures already obsolete. As a solution, the use of ballast and sleepers out of use as aggregates for the manufacture of slab track is proposed. A validation of this material as an aggregate for the manufacture of slab track is proposed, it is focused on comparing its fatigue strength with that of a standardized aggregate. For this, a series of LOCATI fatigue tests mixed with CT analyses, to see the evolution of the damage suffered by the sample, is carried out.Los autores agradecen la financiación recibida para la realización de este trabajo al Programa Estatal de Investigación, Desarrollo e Innovación orientada a los Retos de la Sociedad en el marco del acuerdo de subvención MAT2014-57544-R, financiado por el Gobierno de España, Ministerio de Economía y Competitividad

Determination of the optimum amount of superplasticizer additive for self-compacting concrete

ABSTRACT: Self-compacting concrete modifies its workability with small variations in the amount of superplasticizer additive. For this reason, large number of tests are required to monitor its workability. In order to determine the appropriate amount of additive for a single mix, the evolution of the power consumption of the concrete mixer during the addition of small amounts of additive to the concrete was analyzed. These results were compared both with typical workability characterization for self-compacting concrete and with the saturation point results, determined by the Marsh cone method. After this comparison, a good correlation was obtained between the results from the traditional tests and the proposed ?concrete mixer method?Funding: This research was funded by Spanish Ministry of Economy and Competitiveness of Spain, grant number MAT2014-57544-R”

Analysis of the environmental degradation effects on the cables of La Arena bridge (Spain)

After nearly 25 years of service, some of the wires of the tendons of ?La Arena? bridge (Spain) started to exhibit the effects of environmental degradation processes. ?La Arena? is cable-stayed bridge with 6 towers and a reference span between towers of about 100 meters. After a maintenance inspection of the bridge, evidences of corrosion were detected in some of the galvanized wires of the cables. A more in-deep analysis of these wires revealed that many of them exhibited loss of section due to the corrosion process. In order to clarify the causes of this degradation event and to suggest some remedial actions, an experimental program was designed. This program consisted of tensile and fatigue tests on some strand samples of the bridge together with a fractographic analysis of the fracture surfaces of the wires, its galvanized layer thickness and some hydrogen measurements (hydrogen embrittlement could be another effect of the environmental degradation process).Once the type and extension of the flaws in the wires was characterized, a structural integrity assessment of the strands was performed with the aim of quantifying the margins until failure and establishing some maintenance recommendations

Incorporación de escorias siderúrgicas en hormigones autocompactantes de altas prestaciones

El acero en España, se realiza mayoritariamente en hornos eléctricos de arco generando el 80% de la totalidad de las escorias de todo el proceso siderúrgico. Las partículas de escorias de horno eléctrico se caracterizan por su morfología irregular y su magnífico comportamiento mecánico, en esta Tesis Doctoral, se ha planteado llevar al límite el comportamiento mecánico de las escorias diseñando hormigones de alta resistencia. Además de la presencia de una acería en las cercanías de Santander, se encuentra una planta de fundición de hierro dúctil con un horno de cubilote de viento caliente. Los residuos retirados del horno son transportados en su totalidad al vertedero. Siguiendo la filosofía de valorización de subproductos industriales y la demanda de finos del hormigón autocompactante, en esta investigación, se ha propuesto aprovechar este residuo mediante su valorización e incorporación como adición. El objetivo final de esta Tesis es la fabricación de hormigones autocompactantes de elevada resistencia y baja permeabilidad mediante la incorporación de escorias de horno eléctrico como árido grueso y fino, así como también, de la escoria de cubilote, tras ser valorizada, como adición

Self-compacting recycled aggregate concrete using out-of-service railway superstructure wastes

Slab track is replacing obsolete ballasted track. This work proposes crushing out-of-service ballast and sleepers for use as aggregates for constructing the slab track. Three kinds of recycled self-compacting concretes were designed; the first one with aggregates from crushed ballast, the second one with aggregates from crushed sleepers and the third one with both kinds of aggregates in the proportion they appear in the track. The mechanical and durability properties of these concretes were analysed. The durability test was focused on freeze-thaw and drying-wetting cycles. The results obtained lead to the conclusion that out-of-service track could be used to build the new one, closing the loop.Spanish Ministry of Economy and Competitiveness for financing the project MAT2014-57544-R