Characterization of fly ash reactivity in hydrating cement by neutron scattering

2009 ◽  
Vol 24 (7) ◽  
pp. 2435-2448 ◽  
Author(s):  
Walairat Bumrongjaroen ◽  
Richard A. Livingston ◽  
Dan A. Neumann ◽  
Andrew J. Allen
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Neutron Scattering ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Pozzolanic Reaction ◽  
Effective Density ◽  
Partial Replacement ◽  
Cement Pastes

Partial replacement of hydrating Portland cement by fly ash produces competing effects: it contributes calcium hydrate silicate (C-S-H) gel through the pozzolanic and alkali-activated reactions but dilutes the contribution of the main Portland cement reaction. To investigate this, two neutron-scattering methods were applied to density-fractionated lignite-type and bituminous-type fly ash/Portland cement pastes (20% by mass replacement). Small-angle neutron scattering (SANS) measured the effect of the fly ash on the fractal C-S-H microstructure, whereas inelastic neutron scattering (INS) measured the pozzolanic reaction in terms of calcium hydroxide (CH) consumption. The CH consumption increased with the effective density fraction, and the fractal microstructure evolved more slowly for all fly ash mixes compared with the pure cement control. However, gel volume measured by SANS showed no correlation with the CH consumption measured by INS. The implications of these results are discussed.

Influence of Physicochemical Properties of Sugarcane Bagasse Ash (SCBA) in Portland Cement Hydration

2018 ◽  
Vol 765 ◽  
pp. 324-328
Author(s):  
Tiago Assunção Santos ◽  
José da Silva Andrade Neto ◽  
Vitor Souza Santos ◽  
Daniel Véras Ribeiro
Keyword(s):  
Portland Cement ◽  
Sugarcane Bagasse ◽  
Cement Hydration ◽  
New Technologies ◽  
Pozzolanic Reaction ◽  
Cement Industry ◽  
Partial Replacement ◽  
Cement Pastes ◽  
Sugarcane Bagasse Ash ◽  
Portland Cement Hydration

Due to the concern with the environmental impacts caused by the gases emitted by the cement industry and by the inadequate disposal of wastes generated in the sugar-alcohol industry, such as sugarcane bagasse ash (SCBA), a search for the development of new technologies, which are less aggressive to the environment and that propose feasible alternatives, began in order to reuse these wastes properly. Among these alternatives is the reuse of SCBA as partial replacement to cement or as addition to cementitious matrices. In this way, the present research has the objective of analyzing the influence of SCBA obtained by the calcination of sugarcane bagasse (SCB), at 600°C, in the process of Portland cement hydration. Initially, the SCBA was characterized physically, chemically and mineralogically, and then cement pastes with 20% and 35% substitution contents were elaborated, besides the reference paste, which were analyzed through X-ray diffraction (XRD) and thermogravimetric (TG) techniques. The results obtained show that there is a consumption of portlandite as a consequence of the use of SCBA, evidencing the pozolanicity of these ashes. In the pastes with 35% substitution content, there was an intense consumption of the portlandite, indicating, in this proportion, the pozzolanic reaction was more intense.

Characterization of the spin-Peierls gap in CuGeO3 by means of inelastic neutron scattering

1995 ◽  
Vol 213-214 ◽  
pp. 281-283 ◽  
Author(s):  
O. Fujita ◽  
M. Nishi ◽  
J. Akimitsu ◽  
H. Okumura ◽  
K. Kakurai ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron

scholarly journals Compressive Strength of High-Volume Fly Ash (HVFA) Concrete as a Function of Lime Water and Curing Time

2021 ◽  
Author(s):  
Chin Mei Yun ◽  
Md. Rezaur Rahman ◽  
Kuok King Kuok ◽  
Mohd Elfy Mersal ◽  
Colin Ngu Ker Liing ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Portland Cement ◽  
High Volume ◽  
Partial Replacement ◽  
Curing Time ◽  
Additional Information ◽  
Lime Water ◽  
High Volume Fly Ash

Abstract The compressive strength of high-volume fly ash (HVFA) concrete with varied volume percentages of 40%, 50%, and 60% was examined utilizing low calcium fly ash (Class-F) as a partial replacement for regular Portland cement in this study. On the 7th, 28th, and 56th days, the compressive strength is tested. At the 7th and 28th days, the influence of saturated lime water on the compressive strength of HVFA concrete is evaluated. The inclusion of fly ash as a replacement for Portland cement reduces the compressive strength of the HVFA concrete, according to the findings. At the 56th day, the HVFA concrete with 40% fly ash substitution has a compressive strength equivalent to the regular weight concrete. At the 28th day, it was discovered that saturated lime water was helpful in maximizing the strength of HVFA concrete with 50% fly ash substitution. There was additional information about the characterization of HVFA concrete.

Characterization of the Interaction of Hydrogen with Iridium Clusters in Zeolites by Inelastic Neutron Scattering Spectroscopy

1994 ◽  
Vol 351 ◽  
Author(s):  
J.M. Nicol ◽  
T.J. Udovic ◽  
R.R. Cavanagh ◽  
Z. Xu ◽  
S. Kawi ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Inelastic Neutron Scattering ◽  
Hydrogen Uptake ◽  
Inelastic Neutron ◽  
Metal Nanoclusters ◽  
Zeolite Nay ◽  
Kl Zeolite ◽  
Hydrogen Bound ◽  
Inelastic Neutron Scattering Spectroscopy

ABSTRACTIncoherent inelastic neutron scattering (IINS) measurements of hydrogen bound to Ir6 clusters in the nanoscale pores of zeolite NaY and similar clusters in KL zeolite are reported. On the basis of hydrogen uptake measurements and the observation of peaks in the IINS spectra, we infer that hydrogen is bound to the metal nanoclusters in the zeolite pores. The HINS data for both zeolites are similar and consistent with the presence of IrH2 species.

Diffusion Behavior of Organic Carbon and Iodine in Low-heat Portland Cement Containing Fly Ash

2008 ◽  
Vol 1124 ◽  
Author(s):  
Taiji Chida ◽  
Daisuke Sugiyama
Keyword(s):  
Fly Ash ◽  
Organic Carbon ◽  
Portland Cement ◽  
Effective Diffusion ◽  
Cementitious Materials ◽  
Pozzolanic Reaction ◽  
Radioactive Waste Disposal ◽  
Hardened Cement ◽  
Cement Pastes ◽  
Engineered Barrier

AbstractThe diffusion of radionuclides in cementitious materials used as an engineered barrier is an important parameter in the performance assessment of the sub-surface repository system used for low-level radioactive waste disposal in Japan. In particular, organic carbon-14 and iodine-129 would provide large contributions to the dose evaluation, because of their low ability to be adsorbed on cementitious materials. In this study, the diffusion of acetate and iodide in hardened cement pastes was examined by through-diffusion experiments. Low-heat Portland cement containing 30 wt% fly ash (FAC), which is a candidate cement material for the construction of the sub-surface repository, was prepared for the diffusion experiments. The effective diffusion coefficients, De, of the trace ions for hardened FAC cement pastes were estimated to be on the order of 10-13 m2 s-1 at the beginning of the diffusion experiments. Then, the rate of diffusion of the trace ions decreased over the experimental period of 1-15 months. This is probably due to the change in the microstructure of the FAC as the result of a pozzolanic reaction. After a few months, the values of De were estimated to be on the order of 10-14 m2 s-1. These results suggest that an engineered barrier made of FAC can act as an effective barrier inhibiting the diffusion of trace ions such as organic carbon and iodine.

Microstructure and Characterizations of Portland-Bottom Ash-Silica Fume Cement Pastes

2008 ◽  
Vol 55-57 ◽  
pp. 629-632 ◽  
Author(s):  
W. Wongkeo ◽  
W. Thawornson ◽  
Arnon Chaipanich
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Silica Fume ◽  
Power Plants ◽  
Thermal Power ◽  
Bottom Ash ◽  
Pozzolanic Reaction ◽  
Cement Particle ◽  
Cement Pastes

This research investigated the microstructure and characterization of Portland-bottom ash-silica fume cement pastes. Bottom ash, a by – product from coal-fired thermal power plants, was obtained from Mae Moh power plant, Lampang, Thailand. It currently exists as waste approximately 1.5 MT per year and has not been put to use. Unlike its counterpart, fly ash, which is recognized as an alternative material used to replace part of Portland cement. Silica fume, a nanomaterial from ferrosilicon industry, is nanoparticle and highly amorphous. It is highly pozzolanic reaction and could improve properties of Portland-bottom ash cement pastes. Thus, this research investigated the effect of silica fume on microstructure and characterization of Portland-bottom ash-silica fume cement pastes. The ratios of bottom ash used to replace Portland cement were 0, 10, 20 and 30 percent by weight and silica fume was added at 5 and 10 percent by weight. Compressive strength test was then carried out. SEM and TGA were used to study the microstructure of Portland-bottom ash-silica fume cement pastes. The results show that, the compressive strength of Portland-Bottom ash-silica fume cement pastes increased with added silica fume at 5 and 10 percent. SEM micrographs show C-S-H gel and silica fume around the cement particle in Portland-bottom ash-silica fume cement pastes which gives a highly dense and less porous microstructure. TGA graphs show Ca(OH)2 decreased with silica fume content.

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