C-(N)-S-H and N-A-S-H gels: Compositions and solubility data at 25°C and 50°C

Abstract Calcium silicate hydrates containing sodium [C–(N)–S–H], and sodium aluminosilicate hydrates [N–A–S–H] are the dominant reaction products that are formed following reaction between a solid aluminosilicate precursor (eg, slags, fly ash, metakaolin) and an alkaline activation agent (eg NaOH) in the presence of water. To gain insights into the thermochemical properties of such compounds, C–(N)– S–H and N–A–S–H gels were synthesized with compositions: 0.8≤Ca/Si≤1.2 for the former, and 0.25≤Al/Si≤0.50 (atomic units) for the latter. The gels were characterized using thermogravimetric analysis (TGA), scanning electron microscopy with energydispersive X-ray microanalysis (SEM-EDS), and X-ray diffraction (XRD). The solubility products (KS0) of the gels were established at 25°C and 50°C. Selfconsistent solubility data of this nature are key inputs required for calculation of mass and volume balances in alkali-activated binders (AABs), and to determine the impacts of the precursor chemistry on the hydrated phase distributions; in which, C–(N)–S–H and N–A–S–H compounds dominate the hydrated phase assemblages. KEYWORDS calcium silicate hydrate, cements, geopolymers, solubility, thermodynamic

The Combined Effect of the Initial Cure and the Type of Cement on the Natural Carbonation, the Portlandite Content, and Nonevaporable Water in Blended Cement

The aim of this work is to better understand the physical and chemical phenomena involved in hydrated mix (clinker + addition) during the natural carbonation process, to characterize cement with supplementary cementitious materials (SCMs) under various curing environment. The prepared cement pastes were characterized by thermogravimetric analysis. The results showed a considerable influence of the environment on the properties of mortars and cement and a perfect correlation between compressive strength, natural carbonation, nonevaporable water, and portlandite content. It was observed that the reduction of the curing period makes the mortars more sensitive. The kinetics of process was evaluated from Ca(OH)2 content and nonevaporable water contained in mortars. These two parameters reflect the hydration progress of the water/cement ratio studied. The weight loss due to Ca(OH)2 decomposition, calculated by DTA/TG analysis, shows the effect of the pozzolanic reaction and the natural carbonation. The supplementary cementitious materials (SCMs) play a considerable role in the slowing down of the aggression environment

苯并咪唑类光电功能配合物的研究进展

主要概述了苯并咪唑类光电材料的研究进展。苯并咪唑类配合物的电致发光材料成膜性好、热稳定性高和色纯度高,但发光效率、寿命等仍偏低,发光机理尚不清楚;苯并咪唑类配合物具有良好的刚性平面结构和丰富的π电子,选择合适的离子掺杂,有可能得到高效的发光材料;苯并咪唑类配合物还可用于制备有机太阳能电池,其钌配合物的染料敏化太阳能电池保持着最高的光电转化效率

Micro/nano-structural evolution in blended cement paste due to progressive deionised water leaching

This study investigates the structural evolution of the blended cement pastes at micro-, nano-, and atomic-scale due to environmental factors, such as, water leaching, ageing and curing temperature, with the aid of the analytical techniques, i.e. thermal analysis, XRD, SEM, TEM and SS MAS NMR. The water leaching experiments are performed on the one year old WPC cement paste blended with 30% PFA, as well as 13 years old WPC cement paste blended with 30% and 50% PFA. It is observed that the water leaching induces the phase dissolution and precipitation, e.g. CH, anhydrous cement, AFm and TAH dissolution, C-S-H secondary formation and decalcification, AFt secondary formation and dissolution. The microstructure of the cement paste changes from compact feature to dry cracked land like feature. The Op C-S-H transfers from fine fibrillar or foil-like feature to three dimensional net like feature, and the porosity of Ip C-S-H has increased. The aluminosilicate structure changes from single chain to double chain as the chains have cross-linked across the interlayer. It is also observed with higher replacement of PFA, the leaching speed is slower. Additionally, it is observed the chemical composition, the micro- and nano-scale structure evolve with ageing. The effects of curing temperature on OPC:BFS blended cement hydration is studied. It is found that as curing temperature increases: the general microstructure of the cement paste becomes more porous; more slag reacts, and more Ip C-S-H with high Al and Mg forms; and the MCL of aluminosilicate anion chain increases. For comparison, synthetic C-A-S-H is also characterized to better understand the structure of the C-A-S-H in the cement paste, especially the atomic-scale structure

Apuntes sobre el Monasterio del Escorial, sacados de la historia que escribió José de Quevedo

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

The Use of Ternary Blended Binders in High-Consistence Concrete

This study has investigated the feasibility and advantages of using ternary blended binders containing limestone powder (LP), i.e. Portland-limestone cement (PLC), with fly ash (FA) or ground granulated blastfurnace slag (GGBS) in three types of high-consistence concrete i.e. self-compacting concrete (SCC), flowing concrete (FC) and underwater concrete (UWC), concentrating on the hardened mechanical and durability properties. Initially, mix design methods, tests, target fresh properties and constituent materials were selected for each concrete type. In the first stage of the study SCC mixes were formulated with binary and ternary binder blends with up to 80% cement replacement (by volume). The hardened properties of these, i.e. compressive and tensile strength, sorptivity and rapid chloride penetration resistance, were measured and the relationships between these investigated. Optimum replacement levels of GGBS and FA were estimated (40 and 20% respectively), and were used in the subsequent stages of the study on FC and UWC. The main outcomes were: -It is feasible to produce high-consistence concrete using ternary blended binders with LP and GGBS or FA. -It is possible to achieve similar or higher long-term compressive strengths with ternary binder mixes than with binary binder mixes for concrete with low water/cement ratio (<0.4). -A good relationship was obtained between the sorptivity results and the compressive strength which was independent of the concrete type, age and powder composition. -No relationship between the rapid chloride penetration test results and the compressive strength was obtained; the results had a high degree of scatter. There were reductions in the total embodied carbon contents of the concrete mixes with the incorporation of additions. There is scope for further investigating the synergistic effect between limestone powder and ggbs and fly ash to further reduce the Portland cement content leading to greater potential economic and environmental advantages

CO2 capturing CONSTRUCTION materials for climate change mitigation

La contaminación ambiental, el agotamiento de los recursos no renovables, la gran cantidad de residuos generados, el concepto de “usar y tirar/use and throw” y el aumento de los gases efecto invernadero (GHG), especialmente el CO2 que da lugar al calentamiento global está llevando a adoptar políticas favorables con el medio ambiente en muchos países. La “mitigación” tiene como objetivo reducir las emisiones de GEI y aumentar los sumideros de captura y almacenamiento de estos gases. Uno de los métodos propuestos para reducir el CO2 atmosférico es la captura y almacenamiento de carbono (CCS). Otro método es el desarrollo de tecnologías de captura y uso de carbono (CCU). Una de las ventajas de CCU sobre CCS es que le da un valor añadido al CO2 pudiendo ser considerado como un producto comercial. La industria de la construcción es la mayor fuente de emisiones de CO2. Es por ello que, con objeto de reducir estas emisiones, las investigaciones en materiales de construcción con baja huella de carbono son claves para mitigar el cambio climático. En la presente Tesis Doctoral se estudian varias líneas que permitan dar lugar a nuevos materiales de construcción más sostenibles y amigables con el medioambiente: En primer lugar, se estudia un aditivo captador de CO2 (hidrotalcita de MgAlCO3). Una vez obtenidas todas sus propiedades físicas, químicas, microestructurales y su capacidad de captura de CO2, se mezcló en diferentes porcentajes con un mortero monocapa industrial, ya que con objeto de disminuir el nivel de CO2 en la atmósfera las fachadas de edificios presentan una gran superficie que puede ser idónea para la captura de CO2. En segundo lugar se estudia la fase mortero de un hormigón destinado a productos prefabricados no estructurales (adoquines, bovedillas, mobiliario urbano y otros) usando áridos reciclados mixtos de residuos de construcción y demolición y usando como innovación el curado en CO2 (carbonatación acelerada), promoviendo el concepto de economía circular y dando un valor añadido al CO2 como producto comercial. A continuación se extendió el concepto de carbonatación acelerada a productos de hormigón no estructural fabricado “in-situ”, usando agua carbonatada como agua de amasado, siendo esta una estrategia novedad sin precedentes. Además, con objeto de disminuir costes en adquisición de una cámara de curado de CO2, y facilitar el proceso de la carbonatación acelerada también fue estudiado el curado en agua carbonatada de dichos materiales. Por último se estudió la fase mortero de un hormigón destinado a prefabricados no estructurales, pero en este caso sin usar cemento Portland, mediante el proceso de la activación alcalina y el curado en CO2. Dentro de este material se presentaron dos alternativas, la primera de ellas usando MgO para incrementar la capacidad de captura de CO2 de dicho material y la segunda usó como precursor cenizas de fondo procedentes de la incineración de residuos sólidos urbanos, para dar un uso a estos residuos y maximizar de esta forma el concepto de economía circular. Esta investigación presenta 3 nuevos tipos de materiales de construcción con diferentes finalidades y/o aplicaciones, que contribuirían a la mitigación del cambio climático y por tanto a conseguir una construcción más sostenible y respetuosa con el medio ambiente.Environmental pollution, the depletion of non-renewable resources, the large amount of waste generated, the "use and throw" concept and the increase of greenhouse gases (GHG), especially CO2 which leads to global warming is leading to the adoption of environmentally friendly policies in many countries. “Mitigation" aims to reduce GHG emissions and increase GHG capture and storage sinks. One of the proposed methods to reduce atmospheric CO2 is carbon capture and storage (CCS). Another method is the development of carbon capture and use (CCU) technologies. One of the advantages of CCU over CCS is that it adds value to CO2 and can be considered as a commercial product. The construction industry is the largest source of CO2 emissions. Therefore, in order to reduce these emissions, research into low carbon footprint building materials is the key to mitigating climate change. In this Doctoral Thesis, several lines of research are studied in order to give rise to new, more environmentally sustainable construction materials: Firstly, a CO2 capturing additive (MgAlCO3 hydrotalcite) is studied. Once all its physical, chemical and microstructural properties and its capacity to capture CO2 were obtained, it was mixed in different percentages with an industrial one-coat mortar, since in order to reduce the level of CO2 in the atmosphere, building façades have a large surface area that may be suitable for CO2 capture. Secondly, the mortar phase of a concrete for non-structural prefabricated products (paving stones, vaults, urban furniture and others) is studied using mixed recycled aggregates from construction and demolition waste and using CO2 curing (accelerated carbonation) as an innovation, promoting the concept of circular economy and giving added value to CO2 as a commercial product. The concept of accelerated carbonation was then extended to non-structural in-situ products, using carbonated water as the mixing water, an unprecedented new strategy. In addition, in order to reduce the cost of acquiring a CO2 curing chamber and to facilitate the accelerated carbonation process, the curing of these materials in carbonated water was also studied. Finally, the mortar phase of a concrete for non-structural precast concrete was studied, but in this case without using Portland cement, by means of the process of alkaline activation and CO2 curing. Within this material, two alternatives were presented, the first using MgO to increase the CO2 capture capacity of the material and the second using bottom ash from municipal solid waste incineration as a precursor, to make use of this waste and thus maximise the concept of circular economy. This research broadly presents 3 new types of building materials with different purposes and/or applications, which would contribute to climate change mitigation and thus to a more sustainable and environmentally friendly construction