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.

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.

scholarly journals Characterization of Shale Pore Structure by Multitechnique Combination and Multifractal Analysis and Its Significance

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Dengke Liu ◽  
Tao Tian ◽  
Ruixiang Liang ◽  
Fu Yang ◽  
Feng Ye
Keyword(s):  
Pore Structure ◽  
Pore Size ◽  
Multifractal Analysis ◽  
Ordos Basin ◽  
Pore Network ◽  
Size Distributions ◽  
Geochemical Parameters ◽  
Pore Size Distributions ◽  
Wide Range ◽  
Shale Reservoirs

Understanding pore structure would enable us to obtain a deeper insight into the fluid mechanism in porous media. In this research, multifractal analysis by various experiments is employed to analyze the pore structure and heterogeneity characterization in the source rock in Ordos Basin, China. For this purpose, imaging apparatus, intrusion tests, and nonintrusion methods have been used. The results show that the objective shale reservoir contains complex pore network, and minor pores dominant the pore system. Both intrusion and nonintrusion methods detected pore size distributions show multifractal nature, while the former one demonstrates more heterogeneous features. The pore size distributions acquired by low temperature adsorption and nuclear magnetic resonance have relatively good consistence, indicating that similar pore network detection method may share the same mechanism, and the full-ranged pore size distributions need to be acquired by multitechniques. Chlorite has an obvious impact on the heterogeneity of pore structure in narrow pore size range, while illite and I/S mixed layer influence that in wide range. Kerogen index is the fundamental indicators of geochemical parameters. With the decrease of averaged small and middle/large pore radius, the heterogeneity of pore structures increase in narrow and wide ranges, respectively. This work employed a comprehensive methodology based on multitechniques and helps to explore how pore networks affect reservoir quality in shale reservoirs.

scholarly journals Petrophysical Characterizations of Shale Gas Reservoirs of the Ranikot Formation in the Lower Indus Basin, Pakistan

2021 ◽  
Vol 3 (2) ◽  
pp. 103-107
Author(s):  
Kazunori Abe ◽  
Nouman Zobby ◽  
Hikari Fujii
Keyword(s):  
Pore Structure ◽  
Pore Size ◽  
Density Functional ◽  
Gas Flow ◽  
Slip Flow ◽  
Indus Basin ◽  
Size Distributions ◽  
Gas Reservoirs ◽  
Lower Indus Basin ◽  
Pore Size Distributions

The complex pore structure with nano-pores of shale gas reservoirs has an impact on the hydrocarbon storage and transport systems. We examined the pore structure of the shales of the Ranikot Formation in the Lower Indus Basin, Pakistan to investigate the full scaled pore size distributions by using a combination of techniques, mercury injection capillary pressure analysis and low pressure gas adsorption methods using N2 and CO2. Isotherm curves obtained N2 and CO2 adsorptions were interpreted using density functional theory analysis for describing the nano-scaled pore size distributions. The pore geometry of the shales was estimated to be slit-type from the isotherm hysteresis loop shape. The pore size distributions determined the density functional theory showed the dominant pore size of below around 10 nm. The Micro-scale effects such as slippage and adsorption/desorption also significantly influence the gas flow in nano-pore structure. The gas flow regimes in shales are classified into four types Darcy flow, slip flow, transition flow, Knudsen flow based on the value of the Knudsen number. Applying the specific reservoir conditions in Ranikot shale and pore size distribution to the Knudsen number, the gas flow regimes of the Ranikot shales were estimated mostly within the transition and slip flow.

scholarly journals Gas Sensing Properties of Cobalt Titanate with Multiscale Pore Structure: Experiment and Simulation

Sensors ◽  
2020 ◽  
Vol 20 (6) ◽  
pp. 1787
Author(s):  
Mingchun Li ◽  
Baoting Wang ◽  
Aili Tao ◽  
Shengfei Li
Keyword(s):  
Pore Structure ◽  
Pore Size ◽  
Gas Sensing ◽  
Experimental Results ◽  
Diffusion Reaction ◽  
Size Distributions ◽  
Sensing Properties ◽  
Pore Size Distributions ◽  
Gas Sensing Properties ◽  
Cobalt Titanate

A diffusion-reaction coupled model was presented to investigate the effects of multiscale pore structure characteristics on gas sensing properties. A series of CoTiO3 powders with different pore size distributions were fabricated by sol-gel method. Experimental results on cobalt titanate thick films show that a well-defined multiscale pore structure is particularly desired for the improvement of sensing performance, instead of just increasing the specific surface area. The theoretical responses of sensing elements with different pore size distributions were derived and compared with experimental data on CoTiO3 sensors exposed to ethanol. The calculated sensitivities considering the influence of pore size changes were also found to be in agreement with the experimental results. A dimensionless Thiele modulus Th was introduced for assessing the critical point corresponding to the transformation from surface reaction-controlled sensitivity into diffusion-controlled sensitivity.

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