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Back to basics: Nanomodulating calcium silicate hydrate gels to mitigate CO2 footprint of concrete industryWang, X., Ding, S., Ashour, Ashraf, Ye, H., Thakur, V.K., Zhang, L., Han, B. 26 November 2023 (has links)
Yes / To realize the sustainable development of concrete, it is vital to mitigate its consumption and environmental footprint (especially CO2 footprint) from prolonging the service life through upgrading mechanical and durable performances of concrete. Incorporating nanofillers can effectively tailor the microstructures and performances of bulk cement paste and cement paste at interfacial transition zone in concrete. The hydrated calcium silicate (C–S–H) gels account for half of the volume of hardened Portland cement pastes, and they are the fundamental source of overall properties of concrete. However, the underlying mechanisms of nanofillers on C–S–H gels remains unclear. Herein, this paper underpinned the role of 5 types of representative nanofillers in tailoring the nanostructure of C–S–H gels in cement composites. The research results demonstrated that through the nano-core effect, nanofillers induce the formation of two new C–S–H gels in outer hydration products, namely nano-core-shell element doped low-density C–S–H (NEDLD C–S–H) and nano-core-shell element doped high-density C–S–H (NEDHD C–S–H). The indentation modulus/hardness of NEDLD and NEDHD C–S–H reaches 25.4/0.80 GPa and 46.7/2.72 GPa, respectively. Such superior performances of NEDLD and NEDHD C–S–H derive from the existence of nano-core-shell elements in C–S–H gels rather than the increase in C–S–H packing density. In a short-range, nanofillers form nano-core-shell elements by adsorbing silica tetrahedrons during the hydration process, improving the mechanical properties of C–S–H basic building blocks. In the long-range, the nano-core-shell elements modify the nano-scale performances of C–S–H gels in outer hydration products due to the increase of C–S–H gels’ integrality. / The authors would like to thank the funding offered by the National Science Foundation of China (52308236, 51978127, 51908103, and 52368031), National Key Research and Development Program of China (2018YFC070560 and 2017YFC0703410), the China Postdoctoral Science Foundation (2022M720648, 2022M710973, 2022M713497). / The full-text of this article will be released for public view at the end of the publisher embargo on 01 Dec 2024.
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Estudo e caracteriza??o de mat?rias-primas para o desenvolvimento de blocos s?lico-calc?riosAndrade, Jean Carlos Silva 24 March 2009 (has links)
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Previous issue date: 2009-03-24 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The types of products manufactured calcium silicate blocks are very diversified in its characteristics. They include accessory bricks, blocks, products in dense material, with or without reinforcements of hardware, great units in cellular material, and thermal insulating products. The elements calcium silicate are of great use in the prefabricated construction, being formed for dense masses and hardened by autoclaving. This work has for objective develop formulations that make possible the obtaining of calcium silicate blocks with characteristics that correspond the specifications technical, in the State of the Rio Grande of the North, in finality of obtaining technical viability for use in the civil construction. The work studied the availability raw materials from convenient for the production of calcium silicate blocks, and the effect of variations of the productive process on the developed products. The studied raw materials were: the quartz sand from the city of S?o Gon?alo do Amarante/RN, and two lime, a hydrated lime and a pure lime from the city of Governador Dix-Sept Rosado/RN. The raw materials collected were submitted a testes to particle size distribution, fluorescence of X rays, diffraction of X rays. Then were produced 8 formulations and made body-of-test by uniaxial pressing at 36 MPa, and cured for 7 hours at about 18 kgf/cm2 pressing and temperature of approximately 180 ?C. The cure technological properties evaluated were: lineal shrinkage, apparent density, apparent porosity, water absorption, modulus of rupture flexural (3 points), resistance compression, phase analysis (XRD) and micromorphological analysis (SEM). From the results presented the technological properties, was possible say that utilization of hydrated lime becomes more viable its utilization in mass limestone silica, for manufacture of calcium silicate blocks / Os tipos de produtos s?lico-calc?rios fabricados s?o muito diversificados em suas caracter?sticas. Eles incluem tijolos, blocos, produtos acess?rios em material denso, com ou sem refor?os de ferragem, grandes unidades em material celular, e produtos isolantes t?rmicos. Os elementos s?lico-calc?rios s?o de grande utiliza??o na constru??o pr?-fabricada, sendo formados por massas densas e endurecidos em autoclave. Este trabalho teve como objetivo desenvolver formula??es que possibilitem a obten??o de blocos s?lico-calc?rios com caracter?sticas que correspondem ?s especifica??es t?cnicas, no Estado do Rio Grande do Norte, na finalidade de obter viabilidade t?cnica para uso na constru??o civil. O trabalho estudou a disponibilidade de mat?rias-primas convenientes para a produ??o de blocos s?lico-calc?rios, e o efeito das varia??es do processo produtivo sobre os produtos desenvolvidos. As mat?rias-primas estudadas foram: uma areia quartzosa oriunda do munic?pio de S?o Gon?alo do Amarante/RN, e duas cal, uma cal hidratada e uma cal virgem oriundas do munic?pio de Governador Dix-Sept Rosado/RN. As mat?rias-primas coletadas foram submetidas a ensaios de distribui??o de tamanho de part?cula, fluoresc?ncia de raios X, difra??o de raios X. Em seguida foram produzidas 8 formula??es e confeccionados corpos-de-prova por prensagem uniaxial a 36 MPa, e curados durante 7 horas em press?o de aproximadamente 18 kgf/cm2, e temperatura de aproximadamente 180?C. As propriedades tecnol?gicas de cura avaliadas foram: retra??o linear, massa espec?fica aparente, porosidade aparente, absor??o de ?gua, m?dulo de ruptura ? flex?o em 3 pontos, resist?ncia a compress?o, an?lise fases (DRX) e an?lise micromorfol?gica (MEV). A partir dos resultados apresentados das propriedades tecnol?gicas, foi poss?vel afirmar que a utiliza??o da cal hidratada torna-se mais vi?vel sua utiliza??o em massas s?lico-calc?rias, para fabrica??o de blocos s?lico-calc?rios
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