Microstructure and hardness of cement pastes with mineral admixture

Garcia, Dayana Cristina Silva; Soares, Marcela Maira Nascimento de Souza; Bezerra, Augusto César da Silva; Aguilar, Maria Teresa Paulino; Figueiredo, Roberto B.

doi:10.1590/s1517-707620170002.0145

Cited by 13 publications

(9 citation statements)

References 40 publications

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“…7. The images 7a-c show that the RC microstructure is mainly composed of calcium silicate hydrate (C-S-H) that surround fine aggregate particles (Agr) and other hydrated compounds such as calcium hydroxide lamellar particles (CH), monosulfate (AFm) and needle-shaped particles of ettringite (AFt) 12,[94][95][96][97] . In addition, C-S-H on the surface of calcium hydroxide crystals appear to have been detected (Fig.…”

Section: Resultsmentioning

confidence: 99%

Influence of quartz powder and silica fume on the performance of Portland cement

Tavares

Costa

et al. 2020

Sci Rep

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Supplementary cementitious materials interact chemically and physically with cement, influencing the formation of hydrate compounds. Many authors have analyzed the filler and pozzolanic effect. However, few studies have explored the influence of these effects on hydration, properties in the fresh and hardened states, and durability parameters of cementitious composites separately. This study investigates the influence of the replacement of 20% of Portland cement for silica fume (SF) or a 20-µm medium diameter quartz powder (QP) on the properties of cementitious composites from the first hours of hydration to a few months of curing. The results indicate that SF is pozzolanic and that QP has no pozzolanic activity. The use of SF and QP reduces the released energy at early times to the control paste, indicating that these materials reduce the heat of hydration. The microstructure with fewer pores of SF compounds indicates that the pozzolanic reaction reduced pore size and binding capability, resulting in equivalent mechanical properties, reduced permeability and increased electrical resistance of the composites. SF and QP increase the carbonation depth of the composites. SF and QP composites are efficient in the inhibition of the alkali-aggregate reaction. The results indicate that, unlike the filler effect, the occurrence of pozzolanic reaction strongly influences electrical resistance, reducing the risk of corrosion of the reinforcement inserted in the concrete.

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Section: Resultsmentioning

confidence: 99%

Influence of quartz powder and silica fume on the performance of Portland cement

Tavares

Costa

et al. 2020

Sci Rep

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“…Independent of these parameters, a series of simultaneous and successive reactions are responsible for the gain of consistency or loss of workability, which generates the consolidation of suspensions and consequent resistance gain [22]. Furthermore, understand the microstructure of cement pastes is important to understand the effect of various conditions on the hydration process [23].…”

Section: Introductionmentioning

confidence: 99%

Effect of the water/binder ratio on the hydration process of Portland cement pastes with silica fume and metakaolin

Pereira

Souza

Capuzzo

et al. 2022

Rev. IBRACON Estrut. Mater.

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The microstructure of cement pastes is important to understand the effect of some parameters in the hydration process. In this context, this study had as objective to evaluate the effect of different water/binder (w/b) ratios in the hydration process of cementitious pastes produced with and without incorporation of silica fume and metakaolin. The pastes were obtained with water/binder ratios of 0.3, 0.4 e 0.5, with replacement, by weight, of Portland cement for silica fume and metakaolin, in the contents of 10% and 20%, respectively. It was performed the X-ray diffraction test of the pastes in the ages of 1, 3, 7, and 28 days, to evaluate the hydration evolution of the cementitious materials. According to the results obtained, it was observed that the cementitious pastes presented similar mineralogical phases, except for the pastes containing metakaolin due to the formation of new aluminate phases. With the increase of the water/binder ratio, the pozzolanic reactions and hydration occurred in greater proportion, standing out the metakaolin with greater reactivity.

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“…As principais propriedades dos materiais cimentícios de alto desempenho (f ck > 50 MPa) no estado endurecido são elevada resistência mecânica e elevada durabilidade. Essas propriedades geralmente são alcançadas com a produção de materiais cimentícios com baixa relação água/aglomerante (a/agl) e com a utilização de materiais cimentícios suplementares (MCSs) altamente reativos e nanomateriais [1][2][3][4][5][6][7].…”

Section: Introductionunclassified

Efeito da ultrasonicação da sílica ativa e da nanossílica coloidal em pastas de cimento

Fraga¹,

Rêgo²,

Capuzzo³

et al. 2020

Matéria (Rio J.)

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RESUMO Os materiais cimentícios de alto desempenho podem ser produzidos com a utilização de sílica ativa (SA) e de nanossílica (NS). Devido ao pequeno tamanho de suas partículas, esses materiais tendem a se aglomerar, diminuindo os seus potenciais reativos. Alguns pesquisadores estudaram métodos para dispersar essas partículas como ultrasonicadores e misturadores rotacionais, porém ainda é necessário realizar estudos sobre esses materiais, principalmente sobre o efeito da ultrasonicação da nanossílica coloidal. Dessa forma, esse estudo teve como objetivo avaliar o efeito da ultrasonicação (uso de ultrassom de alta energia) da sílica ativa e da nanossílica coloidal em pastas de cimento. Foram estudadas cinco pastas, sendo uma referência com 100% de cimento Portland CP V-ARI e as outras quatro substituindo 2% e 10% do cimento Portland por nanossílica coloidal e por sílica ativa, respectivamente, em seu estado natural e após a ultrasonicação. Foram realizados os ensaios de resistência à compressão, análise termogravimétrica (ATG), espectroscopia no infravermelho e porosimetria por intrusão de mercúrio (PIM) nas pastas. Os resultados mostraram que a utilização da NS coloidal em substituição ao cimento Portland aumentou a produção de C-S-H, o refinamento dos poros e a resistência à compressão das pastas, porém a utilização da SA em seu estado natural aumentou o tamanho dos poros e diminuiu o desempenho mecânico das pastas devido à aglomeração de suas partículas. Ao ultrasonicar a SA, houve maior produção de C-S-H, refinamento dos poros e maior resistência à compressão quando comparada com a pasta com SA sem o processo de ultrasonicação, comprovando a efetividade desse método para a dispersão dessas partículas. Apesar disso, a ultrasonicação da NS coloidal não resultou em diferenças significativas na microestrutura e de desempenho mecânico das pastas.

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Microstructure and hardness of cement pastes with mineral admixture

Cited by 13 publications

References 40 publications

Influence of quartz powder and silica fume on the performance of Portland cement

Influence of quartz powder and silica fume on the performance of Portland cement

Effect of the water/binder ratio on the hydration process of Portland cement pastes with silica fume and metakaolin

Efeito da ultrasonicação da sílica ativa e da nanossílica coloidal em pastas de cimento

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