Development of cementitious matrix materials, with improved performance, incorporating by-products from the steelmaking industry

275 p.One of the most important industries in the north of Spain, especially in the BasqueCountry, is the steelmaking industry. The production of steel in electric arc furnaces,prevalent in this small region generates huge amounts of industrial steelmaking wastethat have to be properly managed. For many years, the Electric Arc Furnace (EAF) slagsgenerated by the steelmaking industry have been dumped as waste material in landfillsites. Nevertheless, many researchers have been investigating ways of standardizingthe use of EAF slag in construction and civil engineering, so that it can be used asaggregate in hydraulic and bituminous mixes. In this way, dumping sites will berelieved of this waste and the consumption of natural resources will be decreased.In this PhD thesis, a step forward has been taken towards standardization of the re-useof waste materials from the steelmaking industry as raw materials in the manufactureof hydraulic mixes for their use in the construction industry. It has been demonstratedthat, with the correct mix design, EAF slag concrete of the desired workability may bemanufactured and that it can even perform well in real-scale structural elements.Real-scale Reinforced Concrete (RC) beams with both pumpable and self-compactingconcretes have been manufactured to achieve this goal. Following the sustainabilityapproach, it was decided to manufacture the beams, not only with the standardPortland cement type I, but also with cement type IV with the addition of fly ash, inorder to manufacture more sustainable concretes.The decision to work firstly with small samples and to finish the work with real-scaleelements was taken to realize this objective. The experimental methods developed toreach the final objective have been divided into three chapters in this PhD thesis. Eachchapter has introduced a different level of scale that has broadened the investigation.The introductory chapters have presented the scope of the research and a fulldescription of the materials and methods used in the development of the thesis.In the first part (Chapter 4), the work performed on mortar mixes has been presented.Firstly, the interaction of the steel slags with cement type IV was analyzed bymanufacturing mixes with different dosages and developing mechanical and durabilitytests. The mechanical properties displayed an excellent behavior.Subsequently, the manufacture of self-compacting mortar mixes has been presented.It is essential to obtain a good mortar paste, in order to manufacture self-compactingconcretes. Several mortar mixes were manufactured and their fresh propertiesanalyzed. The hardened properties were also evaluated, achieving strengths of up to100 MPa, and the mixtures manufactured with EAF slag aggregate displayed superiorbehavior to mixtures manufactured with natural aggregates. This effect is aconsequence of a suitable mortar microstructure, as is evident from the MIP and CATanalyses. Accelerated aging tests were also performed on the self-compacting mortarmixes, demonstrating the innocuous effect of EAF slag.In the second part (Chapter 5), the studies on pumpable and self-compacting concretemixes with EAF slag added as aggregate have been presented. An in-depth analysis ofthe workability of self-compacting mixes has shown the essential need for carefulcontrol of the fine fraction and selection of a compatible chemical admixture to attainthe required flowability. A numerical simulation of the viscous flux of these selfcompactingmixes has been proposed, reporting very acceptable results. Themechanical properties of these concretes indicated good performance and the analysisof some SEM observations of the fracture surfaces on the SCC-EAFS concrete revealedsignificant features, which help us to understand their structure and mechanicalbehavior.An extensive testing regime to assess the durability of these concretes has also beendescribed. Some classical tests, such as freezing-thawing and drying-wetting, wereconducted until noteworthy deterioration was appreciated in the mixes. Singular tests,such as immersion in sea water in the tidal zone, and a study on reinforcementcorrosion in marine environment, were also performed to evaluate the quality andusefulness of this kind of concrete. The results have demonstrated that EAF slagconcretes behave in a satisfactory way in these environments.In the last part (Chapter 6), the manufacture and performance of real-scale EAF slagreinforced beams has been investigated. These beams were manufactured withpumpable and self-compacting concretes and, for each consistency, cement type I andcement type IV were used for manufacturing different mixes. All the mixes displayedgood fresh behavior during the casting period, producing beams without anyhoneycomb. The flexural behavior of the beams was analyzed and yielded resultssimilar to analytical values calculated with the existing formulation. The long-termdeflection of the beams was evaluated and all the beams performed well over the fullduration of the test.Analyzing the general conclusions drawn from this research, it can be stated that themain objective of the thesis has been achieved.SCM GRID: Sostenibilidad, Construcción y materiales. Grupo de Innovación y Diseñ

Reduction of COVID-19 Anxiety Levels Through Relaxation Techniques: A Study Carried Out in Northern Spain on a Sample of Young University Students

Since March 14, 2020, Spain has been in a state of alarm due to the crisis created by the outbreak of COVID-19. This measure has led to strict levels of lockdown. This situation has led to an increase in anxiety levels among the younger population. For this reason, an intervention was carried out on university voluntary participants in order to help lower their anxiety levels. Specifically, a telematic workshop was implemented to teach emotional literacy and relaxation techniques combined with the practice of the techniques in an autonomous manner. Anxiety measurements were taken before and after the workshop using the Generalized Anxiety Disorder - 7 (GAD-7) scale. The results show that Jacobson's progressive relaxation techniques, Schultz's autogenic training, abdominal relaxations, and visualizations are effective in lowering the anxiety levels of university students as an alternative to pharmacotherapy

The Well-being of children in lock-down: Physical, emotional, social and academic impact

The Covid-19 pandemic is having an unprecedented impact on societies. In the interest of maintaining social distancing, schools in many countries have closed their doors and children have been confined to their homes. Thus, the objective of the present study was to holistically analyze the well-being of children during a period of full lockdown in Spain, by considering physical, emotional, social, and academic indicators. The scale "Wellbeing of Children in Lockdown" (WCL) was used to measure the well-being of 1225 children from 2 to 12 years old from Northern Spain. The survey was completed by the parents and was designed to analyze children's wellbeing in terms of physical, emotional, social and academic aspects. The results suggest that the general wellbeing of children during lockdown was at an intermediate level. Analysis of the various measures of wellbeing revealed that the lowest levels were obtained for physical activity, along with creative and playful activities. Girls, younger children, and those who have access to an outdoor space showed the greatest levels of well-being. Finally, we discuss the implications of these findings for the well-being of children and, in particular, how this can be improved amid the current Covid-19 crisis.KideOn. Research Group of the Basque Government, Ref.: IT1342-19 (A category) . Open Access funding provided by University of Basque Country

Design and Validation of a Scale for Measuring Well-Being of Children in Lockdown (WCL)

The objective of this study was to create and validate an instrument to measure the well-being of children in lockdown. As a response to the COVID-19 pandemic, and in the interest of maintaining social distancing, millions of people have been confined to their homes, including children, who have been withdrawn from school and barely able to leave their homes. Thus, it would be useful to evaluate, from a holistic perspective, the well-being of children under these challenging circumstances. The participants were 1,046 children, 48.7% of which were boys and 50.7% girls, recruited in the Basque Country (Northern Spain). The scale was answered by their parents. The survey, entitled "Well-being of Children in Lockdown" (WCL), is composed of six subscales: Emotions, Playful and creative activities, Education, Addictions, Routine, and Physical Activity. Exploratory factor analyses indicate that all the reliability indices were acceptable. The survey demonstrated adequate reliability (alpha = 0.804). We were thus able to confirm the validity of this simple instrument for evaluating the well-being of children aged between 4 and 12 years in lockdown situations. The WCL can be regarded as a useful tool to evaluate the well-being of children in lockdown situations.This research was supported by KideOn Research Group of the Basque Government, Ref.: IT1342-19 (A category)

Microstructure and Dimensional Stability of Slag-Based High-Workability Concrete with Steelmaking Slag Aggregate and Fibers

Four high-workability (pumpable and self-compacting) concretemix designs are presented that incorporate steelmaking slagswith additions of both metallic and polymeric fibers. Electric arcfurnace slag (EAFS) as aggregate, and ladle furnace slag (LFS) andground granulated blast furnace slag (GGBFS) as supplementary cementitious material (SCM) are applied to optimize the sustainability ofthe mix design. The main variables in the microstructural analysis, theporosity and the pore structure of the hardened mixes, were assessedwith mercury intrusion porosimetry (MIP), X-ray computed tomography (XCT) and water capillary penetration analysis. Moreover,shrinkage was observed to decrease when adding metallic fibers and LFS. In general, scanning electron microscopy (SEM) observationsrevealed good quality concrete microstructures. Accelerated aging tests at a moderate temperature (72°C) produced a slight lengthening,which affected the dimensional stability of all the mixtures, which was also conditioned by their micro-porosity. The internal damageinduced by this test decreased the brittle fracture strength of the concrete mixes, although the use of GGBFS and LFS moderated thatdamage, due to the increased compliance of the cementitious matrix.The authors wish to express their gratitude for funding this researchwork to the Spanish Ministry of Universities, MInisterio de Cienciae INNovaci ́on (MICINN), Agencia Estatal de Investigaci ́on (AEI),European Union (EU), and European Regional Development Fund(ERDF) (PID2020-113837RB-I00, PID2021-124203OB-I00,RTI2018-097079-B-C31, 10.13039/501100011033, FPU17/03374);ERDF and the Junta de Castilla y Le ́on (BU119P17; UIC-231);European Social Fund (ESF) and Youth Employment Initiative(JCyL) (UBU05B_1274); Sustainable And Resilient ENvironment(SAREN) research group (IT1619-22, the Basque Government);and the University of Burgos [Y135.GI]. Our thanks also go to thecompanies Chryso Additives and Hormor-Zestoa for their ongoingcollaboration with research group members

Shear strength assessment of reinforced concrete components containing EAF steel slag aggregates

Electric Arc Furnace (EAF) slag can be reused as aggregate in Portland cement concrete mixes. The addition of EAFS and other waste co-products (fly ash, blast furnace slag) will modify the binding properties and will, importantly, enhance the global sustainability of such concretes. These mix designs offer acceptable pumpability and self-compaction in the fresh state and can be reinforced with fibers. In this study, eight different concrete mixes are designed within the range of medium-strength concretes (30–50 MPa) and are characterized in both the fresh and the hardened state. Large concrete volumes are used to pour reinforced beams, which are then subjected to small-span high-load tests to evaluate their resistance to shear stress, by analyzing two types of transversal (shear) reinforcement. The tests yielded promising results, contributing additional evidence on the viability of using recycled EAFS aggregate in structural applications. The mechanical behavior of these concretes was closely correlated with the strength predictions calculated with the formulas listed in various international standards.Spanish Ministry of Universities, MICINN, AEI, EU and ERDF [PID2020-113837RB-I00; RTI2018-097079-B-C31; 10.13039/501100011033; FPU17/03374]; the Junta de Castilla y León and ERDF [UIC-231, BU119P17]; Youth Employment Initiative (JCyL) and ESF [UBU05B_1274]; the University of Burgos [grant number SUCONS, Y135.GI], and, finally, our thanks also go to the SAREN research group (IT1619-22, Basque Government)

The study of properties and behavior of self compacting concrete containing Electric Arc Furnace Slag (EAFS) as aggregate

Electric Arc Furnace Slag (EAFS) can be efficiently reused as aggregate in the production of high-volume batches of hydraulic concrete mixes that show interesting properties in both the fresh and the hardened state. Mixtures containing EAFS aggregate in proportions of nearly 50% by volume are prepared for use as pumpable and self-compacting mixes with consistency classes of S4 and SF2, respectively. Characterization of the mixtures is presented, examining practical aspects such as thixotropy, segregation in the fresh state (under 6%), and mechanical and microstructural evolution in the hardened state. The results yielded compressive strengths of approximately 60 MPa and elastic moduli of 38 GPa after one year. Finally, real-scale flexural elements are cast and subjected to sustained loading tests of moderate intensity. Long-term deflection values were approximately 50% (pumpable mixes) and less than 40% (self-compacting mixes) of the maximum admissible values specified in current standards.The authors wish to express their gratitude to: the Vice-Rectorate of Investigation of the University of the Basque Country(UPV/EHU) [PIF 2013]; the Vice-Rectorate of Investigation of theUniversity of Burgos [SUCONS]; the Junta de Castilla y León (Regio-nal Government) for funding the UIC-231 group through projectBU119P17 partially supported by FEDER funds; Project RTI2018-097079-B-C31 (MCIU/AEl/EU) and the UPV/EHU [PPGA19/61].Moreover, we are also grateful to both the Basque Governmentresearch group (IT1314-19) and the companies Chryso Additivesand Hormor-Zestoa for their ongoing collaboration with the pre-sent research group

Statistical Approach for the Design of Structural Self-Compacting Concrete with Fine Recycled Concrete Aggregate

The compressive strength of recycled concrete is acknowledged to be largely conditioned by the incorporation ratio of Recycled Concrete Aggregate (RCA), although that ratio needs to be carefully assessed to optimize the design of structural applications. In this study, Self-Compacting Concrete (SCC) mixes containing 100% coarse RCA and variable amounts, between 0% and 100%, of fine RCA were manufactured and their compressive strengths were tested in the laboratory for a statistical analysis of their strength variations, which exhibited robustness and normality according to the common statistical procedures. The results of the confidence intervals, the one-factor ANalysis Of VAriance (ANOVA), and the Kruskal–Wallis test showed that an increase in fine RCA content did not necessarily result in a significant decrease in strength, although the addition of fine RCA delayed the development of the final strength. The statistical models presented in this research can be used to define the optimum incorporation ratio that would produce the highest compressive strength. Furthermore, the multiple regression models offered accurate estimations of compressive strength, considering the interaction between the incorporation ratio of fine RCA and the curing age of concrete that the two-factor ANOVA revealed. Lastly, the probability distribution predictions, obtained through a log-likelihood analysis, fitted the results better than the predictions based on current standards, which clearly underestimated the compressive strength of SCC manufactured with fine RCA and require adjustment to take full advantage of these recycled materials. This analysis could be carried out on any type of waste and concrete, which would allow one to evaluate the same aspects as in this research and ensure that the use of recycled concrete maximizes both sustainability and strength.This research was funded by the following entities and grants: Spanish Ministry MCI, AEI, EU, and ERDF, grants FPU17/03374 and RTI2018-097079-B-C31; the Junta de Castilla y León and ERDF, grant BU119P17 awarded to research group UIC-231; Youth Employment Initiative (JCyL) and ESF, grant UBU05B_1274; the University of Burgos, grant Y135 GI awarded to the SUCONS group; the University of the Basque Country, grant PPGA20/26; the Basque Government research group IT1314-19. Conflicts of Interes

Bending tests on building beams containing electric arc furnace slag and alternative binders and manufactured with energy-saving placement techniques

The environmental impact of the building sector is especially relevant during the construction phase. Both the materials and the construction methods that are currently in use must be reconsidered, in order to minimize the environmental impact of concrete-based structures. This research is therefore focused on achieving greener concrete-based building structures. In this context, the feasibility of careful use of materials for concrete manufacture and the use of construction techniques that can facilitate and reduce energy consumption during placement are both studied. To do so, twelve sample beams were prepared using eight different sustainable high-workability structural concretes. The aim was to maximize the use of the by-products that amounted to over 80% of the concrete mass, steelmaking slags, fly ash, and quarry waste, and to employ energy-saving concrete placement techniques. The beams underwent bending tests in which their mechanical behavior and their compliance with the specifications of the most relevant building codes were verified. The results pointed to the feasibility of increased sustainability in the field of building engineering through the suitable use of selected by-products and techniques.Spanish Ministry MCI, AEI, EU and ERDF [RTI2018-097079-B-C31; 10.13039/501100011033; FPU17/ 03374]; the Junta de Castilla y Le´on (Regional Government) and ERDF [UIC-231, BU119P17]; Youth Employment Initiative (JCyL) and ESF [UBU05B_1274]; the University of Burgos [grant number SUCONS, Y135.GI], UPV/EHU (PPGA20/26) and, finally, our thanks also go to the Basque Government research group IT1314-19 and likewise to CHRYSO and HORMOR for supplying the materials for research

Elastic stiffness estimation of aggregate–ITZ system of concrete through matrix porosity and volumetric considerations: explanation and exemplification

The modulus of elasticity of a concrete depends on the elastic stifness of both the cementitious matrix and the aggregate–ITZ system, which includes any slippage mechanisms under loading between the aggregate and the cementitious matrix within the interfacial transition zone (ITZ). A procedure is presented in this paper to estimate the elastic stifness of an aggregate–ITZ system within a cementitious matrix, by considering the relative volumes and the porosities of the concrete components. The method was validated by determining the elastic stifness of both the limestone–ITZ and the electric arc furnace slag (EAFS)–ITZ systems when embedded in a slag-based cementitious matrix. The greater stifness of the EAFS–ITZ system in comparison with the natural aggregate system explained the higher strength and modulus of elasticity of the concrete following additions of EAFS. Moreover, having determined those parameters, the elastic moduli of concretes with a similar cementitious matrix could then be accurately estimated.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. The authors wish to express their gratitude for funding this research work to the Spanish Ministry of Universities, MICINN, AEI, EU and ERDF [PID2020-113837RBI00; PID2021-124203OB-I00; RTI2018-097079-B-C31; 10.13039/501100011033; FPU17/03374]; the Junta de Castilla y León (Regional Government) and ERDF [UIC-231, BU119P17]; the Basque Regional Government through the consolidated research group SAREN [IT1619-22]; Youth Employment Initiative (JCyL) and ESF [UBU05B_1274]; and, fnally, the University of Burgos [Y135.GI]