Influence of Type of Cement and Curing on Carbonation Progress and Pore Structure of Hydrated Cement Pastes

1986 ◽  
Vol 85 ◽  
Author(s):  
Th.A. Bier
Keyword(s):  
Phase Composition ◽  
Fly Ash ◽  
Portland Cement ◽  
Pore Structure ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Blast Furnace Slag ◽  
Cement Pastes ◽  
Furnace Slag

ABSTRACTDifferent series of cement paste specimens were prepared with ordinary portland cement, with portland, blast furnace slag cements having slag contents of 30, 50 and 75% by mass, with commercial fly ash cement and with portland cement containing fly ash additions of 10, 20, 30 and 50% by mass. Moist curing of the specimens varied between 3 and 28 days before the pore size distribution and characteristics of the phase composition were analyzed. Subsequent to curing, the specimens were subjected to drying in air of 65% RH with a controlled CO2 content of 0, 0.03 and 2% CO2 by volume. Depth of carbonation, pore size distribution of the carbonated paste, and the phase composition were investigated after 28 days and 6 months of drying, respectively. The results show that carbonation alters the prevailing pore structure of the hydrated paste. Important parameters are the type of cement used and the duration of curing.

Diffusion and Pore Structure in Portland Cement Pastes Blended with Low Calcium Fly Ash

1985 ◽  
Vol 65 ◽  
Author(s):  
Amitabha Kumar ◽  
Della M. Roy
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Pore Structure ◽  
Pore Size ◽  
Size Distributions ◽  
Cation Diffusion ◽  
Cement Pastes ◽  
Effective Coefficients ◽  
Pore Size Distributions ◽  
Diffusion Rates

ABSTRACTEffective coefficients for the diffusion of Cs+ and Cl− ions accross hardened plates of Portland cement and Portland cement-fly ash blend pastes were measured at 27°, 38° and 60° for samples cured up to 28 d. The porosity and pore size distributions of the same hardened plates were also determined. The fly ash blends show lower anion and cation diffusion rates at higher temperatures, although the porosity is not significantly different from the neat paste. The finer pore size is considered responsible for the slower diffusion in the blends. The electronegative nature of the pore surfaces also contributes to the slower cation diffusion.

Pore Structure Analysis of Portland Cement and Blended Portland Cements Cured under Hydrothermal Conditions

2014 ◽  
Vol 1000 ◽  
pp. 235-238
Author(s):  
Tomáš Ifka ◽  
Martin Palou ◽  
Marta Kuliffayova ◽  
Martin Boháč ◽  
Františka Frajkorová ◽  
...  
Keyword(s):  
Portland Cement ◽  
Pore Structure ◽  
Blast Furnace Slag ◽  
Steam Pressure ◽  
Hydraulic Permeability ◽  
Hydrothermal Conditions ◽  
Cement Pastes ◽  
Hydrothermal Curing ◽  
Hydrate Products ◽  
Furnace Slag

The pore structure of Portland cement pastes cured under different hydrothermal regimes was analyzed. Pore size distribution (PSD), hydraulic permeability coefficient (HK) and porosity (P) were found depending on temperature and steam pressure. With increasing hydrothermal characteristics, the pore structures degraded causing the depletion in compressive strength. Then, blast furnace slag (BFS) and silica fume (SF) were added to PC and cured under similar conditions. It was found that the pore structure was greatly improved. The effect of hydrothermal curing may be interpreted by the intensity and position of the peak, by the length and bimodal characteristic of PSD. The maximum concentration of pores of reference cement paste lies in the range 10 – 103 nm, and changes progressively to the size < 10 nm with increasing addition of BFS and SF. This behavior is attributed mainly to the presence of SF. Microstructure analysis shows hydrate products like needle CSH and CASH, which were stable under hydrothermal curing.

Early-Age Heat Evolution and Pore Structure of Portland Cement Blended with Blast Furnace Slag, Fly Ash or Limestone Powder

2009 ◽  
Vol 405-406 ◽  
pp. 242-246
Author(s):  
Jie Zhou ◽  
Guang Ye ◽  
Klaas van Breugel
Keyword(s):  
Blast Furnace ◽  
Fly Ash ◽  
Portland Cement ◽  
Pore Structure ◽  
Blast Furnace Slag ◽  
Heat Evolution ◽  
Limestone Powder ◽  
Experimental Investigations ◽  
Early Age ◽  
Furnace Slag

Recently, blast furnace slag, fly ash and limestone powder are increasingly used as blending materials in producing concrete. The use of these materials not only has economical and environmental advantages, but also improves the mechanical properties, durability and workability of concrete. In this paper, the results of experimental investigations on the evolution of hydration heat and the development of microstructure of Portland cement blended with blast furnace slag, fly ash or limestone powder are presented. These results show that three blending materials accelerate the hydration of Portland cement, but result in less heat release during the first 72 hours. The Portland cement with blast furnace slag has a denser pore structure than the others.

Carbonation Effects in Hardened Fly Ash Cements

1985 ◽  
Vol 65 ◽  
Author(s):  
Inger Meland
Keyword(s):  
Fly Ash ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Mercury Porosimetry ◽  
Cement Pastes ◽  
X Ray ◽  
Solid Phases

ABSTRACTCarbonation in hardened pastes of fly ash cements, stored in a CO2 atmosphere and exposed to different relative humidities, has been investigated in order to study its effects upon different properties of cement pastes. Thermogravimetry (TG), x-ray diffractometry, SEM, and mercury porosimetry (MIP) have been used to characterize the carbonation phenomenon. The results indicate that different relative humidities in the storage chambers lead to carbonation of different solid phases in the hydrated pastes. This effect is discussed in terms of TG- and x-ray analysis. Changes in pore size distribution due to carbonation have been analyzed by MIP and SEM.

scholarly journals Construction of pore structure and lithology of digital rock physics based on laboratory experiments

2021 ◽  
Vol 11 (5) ◽  
pp. 2113-2125
Author(s):  
Chenzhi Huang ◽  
Xingde Zhang ◽  
Shuang Liu ◽  
Nianyin Li ◽  
Jia Kang ◽  
...  
Keyword(s):  
Pore Structure ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Laboratory Experiments ◽  
Rock Physics ◽  
Reconstruction Method ◽  
Digital Rock Physics ◽  
Digital Rock ◽  
The Core

AbstractThe development and stimulation of oil and gas fields are inseparable from the experimental analysis of reservoir rocks. Large number of experiments, poor reservoir properties and thin reservoir thickness will lead to insufficient number of cores, which restricts the experimental evaluation effect of cores. Digital rock physics (DRP) can solve these problems well. This paper presents a rapid, simple, and practical method to establish the pore structure and lithology of DRP based on laboratory experiments. First, a core is scanned by computed tomography (CT) scanning technology, and filtering back-projection reconstruction method is used to test the core visualization. Subsequently, three-dimensional median filtering technology is used to eliminate noise signals after scanning, and the maximum interclass variance method is used to segment the rock skeleton and pore. Based on X-ray diffraction technology, the distribution of minerals in the rock core is studied by combining the processed CT scan data. The core pore size distribution is analyzed by the mercury intrusion method, and the core pore size distribution with spatial correlation is constructed by the kriging interpolation method. Based on the analysis of the core particle-size distribution by the screening method, the shape of the rock particle is assumed to be a more practical irregular polyhedron; considering this shape and the mineral distribution, the DRP pore structure and lithology are finally established. The DRP porosity calculated by MATLAB software is 32.4%, and the core porosity measured in a nuclear magnetic resonance experiment is 29.9%; thus, the accuracy of the model is validated. Further, the method of simulating the process of physical and chemical changes by using the digital core is proposed for further study.

scholarly journals Coal Fly Ash Derived Silica Nanomaterial for MMMs—Application in CO2/CH4 Separation

Membranes ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 78
Author(s):  
Marius Gheorghe Miricioiu ◽  
Violeta-Carolina Niculescu ◽  
Constantin Filote ◽  
Maria Simona Raboaca ◽  
Gheorghe Nechifor
Keyword(s):  
Fly Ash ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Coal Fly Ash ◽  
High Surface ◽  
Industrial Applications ◽  
Mixed Matrix Membranes ◽  
Co2 Removal ◽  
Mcm 41

In order to obtained high selective membrane for industrial applications (such as natural gas purification), mixed matrix membranes (MMMs) were developed based on polysulfone as matrix and MCM-41-type silica material (obtained from coal fly ash) as filler. As a consequence, various quantities of filler were used to determine the membranes efficiency on CO2/CH4 separation. The coal fly ash derived silica nanomaterial and the membranes were characterized in terms of thermal stability, homogeneity, and pore size distribution. There were observed similar properties of the obtained nanomaterial with a typical MCM-41 (obtained from commercial silicates), such as high surface area and pore size distribution. The permeability tests highlighted that the synthesized membranes can be applicable for CO2 removal from CH4, due to unnoticeable differences between real and ideal selectivity. Additionally, the membranes showed high resistance to CO2 plasticization, due to permeability decrease even at high feed pressure, up to 16 bar.

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