Effect of various superplasticizers on the rheological properties of Portland cement pastes

Papo, A.; Piani, L.

doi:10.1016/j.cemconres.2004.03.017

Cited by 170 publications

(71 citation statements)

References 7 publications

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“…High-range water reducers or superplasticizers (SPs) act reducing the water demand and enhancing the flowability of the fresh mortars, yielding workable materials [3]. SPs present different chemical compositions, such as lignosulfonates, sulfonated melamine-based polymers or polycarboxylate-based compounds (PCE) [4]. The latter are belonging to the last generation of SPs and consist of a main linear backbone (polymethacrylic acid) with carboxylate groups, some of them grafted with side chains with ether functionalities (polyethylene oxide units) [5].…”

Section: Introductionmentioning

confidence: 99%

Assessment of the interaction of polycarboxylate superplasticizers in hydrated lime pastes modified with nanosilica or metakaolin as pozzolanic reactives

Navarro-Blasco

Perez-Nicolas

Fernández

et al. 2014

Construction and Building Materials

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Two polycarboxylate ether copolymers were assessed as superplasticizers (SPs) for hydrated lime pastes modified with two reactive compounds, nanosilica (NS) and ceramic metakaolin (MK). Characterization of the molecular structure of the SPs by Size Exclusion Chromatography, XRD, FTIR and MALDI-TOF (Matrix Assisted LaserDesorption Ionization Time-of-Flight) mass spectrometry was performed. The structures of the polymers were seen to be star-and worm-like shapes. A close relationship was found between the molecular architecture and the flowability of the pastes, being the star-shaped plasticizer the most efficient. Zeta potential assessment allowed us to elucidate a steric hindrance as the main action mechanism for these polymers. The large specific surface area of nanosilica led to a large SPs consumption as compared with metakaolin with lower surface area. However, SPs in MK-lime samples were attached favourably on the C-S-H and aluminate hydrates, so that the dispersing action was greater with respect to NS-lime suspensions.2

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Section: Introductionmentioning

confidence: 99%

Assessment of the interaction of polycarboxylate superplasticizers in hydrated lime pastes modified with nanosilica or metakaolin as pozzolanic reactives

Navarro-Blasco

Perez-Nicolas

Fernández

et al. 2014

Construction and Building Materials

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“…Quando os aditivos a base de ácido policarboxílico são adsorvidos pelas partículas, estes provocaram a defloculação e dispersão do sistema através do efeito eletroestérico, o que favorece a liberação da água antes aprisonada e confere maior fluidez à mistura [16,29]. Os resultados mostraram que a adição de SP atuou mais intensamente sobre a tensão de escoamento do que sobre a viscosidade plástica.…”

Section: Figuraunclassified

“…O comportamento reológico das pastas de cimento no estado fresco depende de vários fatores de natureza distinta [16], como fatores físicos (relação água/cimento, forma e tamanho de partículas de cimento), fatores químicos e mineralógicos (composição do cimento e suas modificações estruturais devido a processos de hidratação), condições de mistura (taxa, tipo de misturador), condições de medição (instrumentos, procedimentos experimentais) e presença de aditivos. Alguns trabalhos [17][18][19][20][21] compararam o efeito das adições minerais (escória de alto forno, cinza volante, sílica ativa) com as pastas de cimento padrão (sem adições).…”

Section: Introduçâounclassified

Comportamento reológico de pastas de cimento com adição de sílica ativa, nanossílica e dispersante policarboxílico

2010

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RESUMONeste trabalho é apresentado um estudo sobre o efeito da adição da sílica ativa (SA), nanossílica (NS) e aditivo dispersante policarboxílico (SP) sobre o comportamento reológico de pastas de cimento (CP V ARI RS). Para fins comparativos com a pasta de referência (REF), foram produzidas pastas com SA, em diferentes teores em massa (0 a 10%) e pastas com 1,0% de NS. Em todas as pastas estudadas (REF, SA e NS) variou-se SP entre 0 a 0,5%, relativos à massa de cimento. Os ensaios foram realizados em um reômetro com geometria de cilindros concêntricos e taxa máxima de cisalhamento aplicada de 100 s -1 . Os aumentos de SP causaram a redução na área de histerese, na viscosidade plástica e na tensão de escoamento, sendo esta última mais influenciada que a viscosidade plástica. Nas pastas cujos resultados foram ajustados por Bingham, as misturas contendo um mesmo teor SP, a tensão de escoamento de Bingham não variou substancialmente, exceto nas pastas com 10% de SA e 0.1 a 0.3% de SP. Para a viscosidade plástica não foi observada tal tendência. Entretanto, NS influenciou significativamente o valor da viscosidade plástica em relação à REF e à SA. Nas pastas cujos resultados apresentaram aproximação satisfatória quando ajustados ao modelo de Bingham e Herschel-Bulkley, para uma mesma dosagem de SA, os aumentos nos teores de SP causaram redução na tensão de escoamento e na viscosidade plástica. O modelo de Bingham descreve adequadamente o comportamento reológico das misturas com a tensão de cisalhamento com valores intermediários, enquanto que o modelo de Herschel-Bulkley é mais adequado para as tensões máxima de cisalhamento elevadas ou reduzidas.Palavras-chaves: silica ativa, nanossílica, pasta de cimento. Rhelogycal behaviour of cement pastes with addition of silica fume, nanosilica and polycarboxilic dispersant ABSTRACTThis article shows the results of an investigation about the effect of silica fume (SF), nanosilica (NS) and superplasticizer (SP) addition on the rheological behavior of CP V ARI RS cement pastes. Cement pastes with different content of SF (0 to 10 wt%) and 1.0 wt% NS were compared to REF (without mineral addition). For all samples studied (REF, NS and SF), SP ranged 0 to 0.5 wt% relative to cement. A rheometer with concentric cylinders geometry was used and the maximum shear rate of 100 s -1 was applied. When SP is added into the mixtures, the hysteresis area, plastic viscosity and yield stress decreased. The latest was more affected than plastic viscosity. When SF was added, the yield stress did not change significantly, except in samples with 10 % SF and SP between 0.1 to 0.3 wt%. In relation to plastic viscosity, the difference was not visualized. However, NS influences more the plastic viscosity than REF and SF. The Bingham model describes properly the rheological behavior of mixtures at intermediate values of shear stress, while the Herschel-Bulkley model are more adequate at high and low values of shear stress.

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“…23 Setting times can be decreased by the addition of setting accelerators and there are many types available from building industry sources. [24][25][26][27][28] However, these additives were not developed for in vivo use and often contain biologically harmful chemicals such as formaldehyde. 29 The chloride and nitrate anions have both demonstrated PC setting acceleration to around 20 min which would be suitable during the vertebroplasty procedure.…”

Section: Introductionmentioning

confidence: 99%

Development of Portland cement for orthopedic applications, establishing injectability and decreasing setting times

2012

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The injectability of Portland cement (PC) with calcium chloride and calcium nitrate additives was investigated using a syringe with a 2 mm aperture for potential clinical applications such as vertebroplasty. Addition of either additive at 10 wt % increased the quantity of cement extruded through the syringe from approximately 25 wt % for the PC standard, to over 95 wt %. 10 wt % additions of either additive also decreased setting times from over 2 h to below 25 min. The compressive strength of the modified cements was all greater than the compressive strength of a human vertebral body. Decreasing either additive to 5 wt % generated compressive strengths after 24 h setting equal to polymethylmethacrylate, the cement used for the majority of vertebroplasty procedures. An initial early exotherm in the chloride cements was coupled with an X-ray diffraction (XRD) peak that indicated the early formation of the ettringite cement phase. In contrast, Fourier transform infrared (FTIR) spectroscopy and XRD data indicated that calcium nitrate may have stimulated early calcium silicate hydrate (CASAH) production (the main strength producing phase of PC). Combining the two additives produced a synergistic effect with cements having increased injectabilities and compressive strengths compared with either addition used individually. This study has demonstrated that by modifying PC with nonproprietary chemicals it was possible to significantly increase cement injectability and reduce setting times whilst maintaining compressive strengths, making PC suitable for potential orthopedic applications.

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Effect of various superplasticizers on the rheological properties of Portland cement pastes

Cited by 170 publications

References 7 publications

Assessment of the interaction of polycarboxylate superplasticizers in hydrated lime pastes modified with nanosilica or metakaolin as pozzolanic reactives

Assessment of the interaction of polycarboxylate superplasticizers in hydrated lime pastes modified with nanosilica or metakaolin as pozzolanic reactives

Comportamento reológico de pastas de cimento com adição de sílica ativa, nanossílica e dispersante policarboxílico

Development of Portland cement for orthopedic applications, establishing injectability and decreasing setting times

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