On the dielectric properties of water confined in cement-like materials

Hydrated cements have pore sizes that range from a few nanometers to microns. The physical and chemical properties of cements (creep, strength, chemical reactivity and shrinkage) are significantly influenced by water molecules in this pore network. Hence, a main task to the cement science is to understand the behavior of water in the pore network to control the physical and chemical properties of cement-based materials. It is known that the structural and physical properties of water near surfaces or confined in small cavities, can be different than those of bulk water. Solid surfaces affect the behavior of water mainly reducing the tetrahedral network of bulk water. However after decades of study, the structure, dynamics and physical properties of this near-surface water remains poorly understood. In this thesis, we focus on the problem of the dynamics of water confined in the nanopores of different sizes of cement-like materials by means of broadband dielectric spectroscopy. This technique has proven to be powerful when studying the reorientation dynamics of polar molecules such as water. In addition, thermal analysis and other spectroscopic techniques have been used to characterize the structure of these materials. This thesis contains four main topics: 1) Dynamics of water in C-S-H gel, the main binding phase of cement materials. From a scientific perspective, the C-S-H gel offers an attractive confinement system where chemical and geometrical effects of the confinement of water can be investigated. In C-S-H gel, the water molecules are trapped mainly in the interlayer space between the highly disordered calcium silicate layers forming the interlayer water. 2) Dynamics of water confined in C-S-H synthesized with the addition of both silica- and amino propyl functionalized nano-particles, before the hydration reaction. 3) Dynamics water confined in tobermorite (natural and synthetic). Structurally Tobermorite is considered an analogue of C-S-H gel. 4) Dynamics of water confined in Portland cements at different water-tocement ratio.The results of this thesis showed that the nature of water in all these systems split into different relaxations (normally three different dynamics) depending on the different chemical environment and/or physical environment where water molecules are situated. Some relaxations were unequivocally related with water molecules relaxing in small gel pores (< 1 nm) whereas other water molecules were structurally linked to the structure of the different materials analyzed. The main relaxation of water confined in C-S-H, C-S-H with the addition of nanoparticles and tobermorite were faster than the so-called universal beta-relaxation of water. By contrast, water in Portland cement was similar to the universal beta-relaxation of water. The water dynamics in Portland cements showed similar characteristics to that observed in other well-defined confinement systems such as molecular sieves or MCM-41. In this thesis, we will discuss the implications of these observations.Gracias al MPC por financiarme.Peer Reviewe

Progress in the influence of recycled construction and demolition mineral-based blends on the physical–mechanical behaviour of ternary cementitious matrices

The serious technical and environmental problems associated with the management of construction and demolition wastes (CDW) have led to a worldwide growing interest in the recycling of that waste stream as secondary raw material for sustainable building applications. This research work investigates the physical and mechanical behaviour of mortars made with ternary cements containing 7% of a binary recycled CDW mixture comprising the fine fraction (<5 mm) of recycled concrete waste (both siliceous and calcareous nature) in combination with recycled laminar glass in three different proportions (1/1, 1/2, and 2/1, respectively). To this end, the chemical composition and fineness of the anhydrous ternary cements were analysed, as well as their behaviour in paste and mortar matrices, in both fresh and hardened states, verifying the requirements established by the applicable standards. The results attest to the viability of using these ternary cements, as their performance is comparable to that of an ordinary Portland cement (OPC), without evidencing any significant dependence on the glass content. The compressive strength values decrease by 7–8% with respect to that of the OPC mortar, revealing the prevalence of the filler effect over the pozzolanic reaction. The ternary cements analysed in this study met the chemical, physical and mechanical requirements for the elaboration of future eco-efficient cements.This research was funded by the Spanish Ministry of Science, Innovation and Universities (MICIU), the Spanish National Research Agency (AEI) and the European Regional Development Fund (ERDF), grant number RTI2018-097074- B-C21-22. The authors are also grateful for the support received from the Spanish Construction and Demolition Waste Recycling Association (RCDA), the Spanish Institute of Cement and its Applications (IECA) and Sika (Madrid, Spain). We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI)

Progress in the influence of recycled construction and demolition mineral-based blends on the physical–mechanical behaviour of ternary cementitious matrices

[Abstract:] The serious technical and environmental problems associated with the management of construction and demolition wastes (CDW) have led to a worldwide growing interest in the recycling of that waste stream as secondary raw material for sustainable building applications. This research work investigates the physical and mechanical behaviour of mortars made with ternary cements containing 7% of a binary recycled CDW mixture comprising the fine fraction (<5 mm) of recycled concrete waste (both siliceous and calcareous nature) in combination with recycled laminar glass in three different proportions (1/1, 1/2, and 2/1, respectively). To this end, the chemical composition and fineness of the anhydrous ternary cements were analysed, as well as their behaviour in paste and mortar matrices, in both fresh and hardened states, verifying the requirements established by the applicable standards. The results attest to the viability of using these ternary cements, as their performance is comparable to that of an ordinary Portland cement (OPC), without evidencing any significant dependence on the glass content. The compressive strength values decrease by 7–8% with respect to that of the OPC mortar, revealing the prevalence of the filler effect over the pozzolanic reaction. The ternary cements analysed in this study met the chemical, physical and mechanical requirements for the elaboration of future eco-efficient cements.Ministerio de Ciencia, Innovación y Universidades; RTI2018-097074-B-C21-2

Kinetics and Mechanisms of Acid-pH Weathering of Pyroxenes

his research has been funded by the Spanish Government (grant CGL2015-70642-R and CGL2015-73103-EXP), the European Commission (ERDF funds and ACT_ERA NET no. 691712, PCI2019-111931-2), the Junta de Andalucia (research group RNM179), and the University of Granada (Unidad Cientifica de Excelencia UCE-PP2016-05). LMG acknowledges funding by the Spanish Government FPI (Grant BES-2016-078468). The authors also thank the personnel of the Centro de Instrumentacion Cientifica (CIC; University of Granada) for assistance with ICP-OES, Micro-CT, and SEM analyses. All experimental results discussed here are presented in the main text and Supporting Information S1. The authors thank the anonymous reviewers for the extremely careful and fruitful revision performed, which has significantly improved the original version of the manuscript.Weathering of primary silicate minerals under acidic conditions occurs in contexts as varied as acid mine drainage, volcanic environments, soils, stone monuments subjected to acid rain or Geological Carbon Storage (GCS). Considering the abundance of pyroxenes on the Earth crust, knowledge of their weathering kinetics and mechanisms may help to optimize carbonate yield in GCS. Here we report experimental results from the reaction of the clinopyroxenes augite and diopside in acidic solutions. Dissolution at far-from-equilibrium conditions results in the formation of etch pits where crack initiate and propagate by stress corrosion and pressure exerted by swelling of an amorphous, gel-like Si-rich phase, which precipitates despite the undersaturation of the bulk solution and whose formation is highly controlled by the heterogeneity of the mineral surface and the local transport mechanism. These precipitates are commonly localized within deep etch pits and cracks, characterized by a low fluid renewal where high Si-concentrations can be reached locally, so that supersaturation with respect to amorphous silica can occur. Cracks and silica precipitates are most abundant in the case of augite weathered in flow-through experiments. This is related to its faster reaction rate compared to diopside, most likely due to its higher iron content. Finally, in the case of diopside an amorphous magnesium silicate hydrate (M-S-H) precursor forms, which represents an indirect evidence of the high pH conditions prevailing at the diopside-solution interface during dissolution.Spanish Government European Commission CGL2015-70642-R CGL2015-73103-EXPEuropean Commission (ERDF fund)European Commission European Commission Joint Research Centre 691712 PCI2019-111931-2Junta de Andalucia RNM179University of Granada (Unidad Cientifica de Excelencia) UCE-PP2016-05Spanish Government BES-2016-07846

Individualization and Electrical Characterization of SiGe Nanowires

SiGe nanowires of different Ge atomic fractions up to 15% were grown and ex-situ n-type doped by diffusion from a solid source in contact with the sample. The phenomenon of dielectrophoresis was used to locate single nanowires between pairs of electrodes in order to carry out electrical measurements. The measured resistance of the as-grown nanowires is very high, but it decreases more than three orders of magnitude upon doping, indicating that the doping procedure used has been effectiv

SiGe nanowires grown by LPCVD using Ga-Au catalysts

The use of Ga-Au alloys as metal catalysts for the growth of SiGe nanowires has been investigated. The grown nanowires are cylindrical and straight, with a defect-free crystalline structure, sharp nanowire-droplet interfaces and an almost constant Ge atomic fraction throughout all their length. These features represent significant improvements over the results obtained using pure A

¡El arte del toreo! : revista cómico-taurina en un acto y cuatro cuadros

Copia digital. Valladolid : Junta de Castilla y León. Consejería de Cultura y Turismo, 201

Ecoturismo: desarrollo sustentable de la provincia Paparo- Venezuela

A través de este trabajo se ofrece una visión geoestratégica para la parroquia Paparo, provincia ubicada en el Estado de Miranda en Venezuela. El proyecto articuló actores comunitarios con miras a consolidar un nuevo tejido social-productivo, que promoviera el eco-turismo como el eje del desarrollo sustentable de la región. Consistió en un trabajo de campo que integró: a) un censo de la población; b) 15 entrevistas y c) 4 focus group. En cuanto a los resultados, se demostró la posibilidad de orquestar inquietudes sociales y consolidar voluntades para generar soluciones concertadas en la búsqueda de mejor calidad de vida para la sociedad, incluyendo necesariamente el ambiente y su protección para las futuras generaciones; ello, apalancado desde la educación para el desarrollo sostenible. Como producto tangible, se ofreció un Plan General, contentivo de dos grandes programas y seis proyectos que constituyen el eje primario para iniciar la consolidación de una plataforma para el pleno desarrollo sustentable de la región.AbstractThrough this work offers a geostrategic for parish Paparo, province located in the State of Miranda in Venezuela. Overview, articulating the community actors with a view to consolidating a new production fabric that promotes eco-tourism as the axis of the sustainable development of the region. It consisted in a field which included: a) a census of the population; b) 15 interviews and c) 4 focus group. As for the results, demonstrated the ability to orchestrate social concerns and consolidate wills to generate agreed solutions in search of a better quality of life for society, necessarily including the environment and its protection for future generations; This is leveraged from the education for sustainable development. As a tangible product, offered a General Plan, containing two large programs and six projects that are the main shaft to start the consolidation of a platform for the sustainable development of the region.Keywords: eco-tourism, sustainable development, education for sustainable development

Traducir el pensamiento en acción: Interfaces cerebro-máquina y el problema ético de la agencia

En este artículo, nos proponemos dos objetivos: el primero, describir la teoría clásica de la agencia intencional y cómo la neurotecnología de las interfaces cerebro-máquina desafía los requisitos de la teoría clásica de la agencia y de la consciencia corporal. La neurotecnología de las interfaces cerebro-máquina funciona implantando electrodos directamente en el área de la corteza motora del cerebro que controla el movimiento, y está diseñada para detectar las señales neuronales asociadas con la intención de moverse, que son después decodificadas por un algoritmo en un computador en tiempo real. Así, una persona podría pensar en mover su pierna o su brazo y la máquina recibiría la información de su pensamiento para traducir el pensamiento en acción, mediante prótesis internas o exoesqueletos. Esto es posible y sus aplicaciones se proyectan tanto sobre la rehabilitación de la funcionalidad motora, como sobre la posibilidad de mejoramiento (enhancement) de las capacidades humanas. Ambas aplicaciones dan lugar a numerosas implicaciones éticas, pero destacamos principalmente una, que denominamos: el problema ético de la agencia. El segundo objetivo del artículo es explorar brevemente la ética algorítmica en el contexto de las interfaces cerebro-máquina y cómo se entienden en este ámbito la autonomía, la responsabilidad y la privacidad informacional. Finalmente, abogamos por la necesidad de un marco ético de principios que regule la neurotecnología, y en tal sentido apelamos a los nuevos neuroderechos

Behaviour and Properties of Eco-Cement Pastes Elaborated with Recycled Concrete Powder from Construction and Demolition Wastes

This work analyses the influence of fine concrete fractions (<5 mm) of different natures —calcareous (HcG) and siliceous (HsT)—obtained from construction and demolition waste (C&DW) on the behaviour of blended cement pastes with partial replacements between 5 and 10%. The two C&DW fractions were characterised by different instrumental techniques. Subsequently, their limefixing capacity and the physico-mechanical properties of the blended cement pastes were analysed. Lastly, the environmental benefits of reusing these fine wastes in the manufacture of future ecoefficient cement pastes were examined. The results show that HsT and HcG exhibit weak pozzolanic activity, owing to their low reactive silica and alumina content. Despite this, the new cement pastes meet the physical and mechanical requirements of the existing regulations for common cements. It should be highlighted that the blended cement pastes initially showed a coarser pore network, but then they underwent a refinement process between 2 and 28 days, along with a gain in compressive strength, possibly due to the double pozzolanic and filler effect of the wastes. The environmental viability of the blended cements was evaluated in a Life Cycle Assessment (LCA) concluding that the overall environmental impact could be reduced in the same proportion of the replacement rate. This is in line with the Circular Economy goals and the 2030 Agenda for Sustainable Development.This research was funded by the Spanish Ministry of Science, Innovation and Un iversities (MICIU), the Spanish National Research Agency (AEI) and the European Regional Development Fund (ERDF), grant number RTI2018-097074- B-C21-22, as well as by the Spanish Training Program and the European Social Fund (MINECO/FSE) [grant number BES-2016-078454]