Influence of Mineral Admixtures on Chloride Threshold Value for the Corrosion of Steel Reinforcement

2011 ◽  
Vol 335-336 ◽  
pp. 1168-1173
Author(s):  
Peng Ping Li ◽  
Jian Bo Xiong ◽  
Zhi Hong Fan ◽  
Sheng Nian Wang
Keyword(s):  
Fly Ash ◽  
Pore Structure ◽  
Average Pore Size ◽  
Threshold Value ◽  
Mineral Admixtures ◽  
Splash Zone ◽  
Tidal Zone ◽  
Average Pore ◽  
Chloride Threshold ◽  
Corrosion Of Steel

The influence of mineral admixtures on chloride threshold value was investigated by EIS method, MIP test and TG test, respectively. The experimental results showed that the chloride threshold value decreased with increasing the fly ash and slag content in composite cementitious. The increasing of fly ash and slag replacement resulted in the decreasing of porosity, average pore size and Ca(OH)2content. The effect of mineral admixtures on the chloride threshold value was the comprehensive results of concrete pore structure and Ca(OH)2content. The chloride threshold value decreased with decreasing the Ca(OH)2content in concrete, and there was an approximate linear relationship between the logarithm of chloride threshold value and the logarithm of CCa(OH)2content when the specimens exposed in tidal zone. The specimen exposed in tidal zone has a higher chloride threshold value than that exposed in splash zone was due to the lower dissolved oxygen around steels in concrete.

Investigate on Pore Structure Characteristics of Reactive Powder Concrete after High Temperatures

2012 ◽  
Vol 174-177 ◽  
pp. 1010-1014 ◽  
Author(s):  
Hong Bin Liu ◽  
Yang Ju ◽  
Kai Pei Tian ◽  
Jin Hui Liu ◽  
Li Wang ◽  
...  
Keyword(s):  
Pore Structure ◽  
Pore Size ◽  
Pore Volume ◽  
Average Pore Size ◽  
Reactive Powder Concrete ◽  
Characteristic Parameters ◽  
Average Pore ◽  
Structure Characteristics ◽  
Temperature Levels ◽  
Reactive Powder

The pore structure characteristics of reactive powder concrete (RPC) were investigated by means of the mercury injection method at seven temperature levels, namely, 20°C, 100°C, 150°C, 200°C, 250°C, 300°C, 350°C, respectively. The characteristic parameters such as porosity, pore volume, average pore size and threshold aperture varied with temperatures were analyzed. The results indicate that the porosity, pore volume, threshold aperture and other characteristic parameters of RPC increased with the temperature increasing.

PORE STRUCTURE CHARACTERIZATION FOR A CONTINENTAL LACUSTRINE SHALE PARASEQUENCE BASED ON FRACTAL THEORY

Fractals ◽  
2019 ◽  
Vol 27 (01) ◽  
pp. 1940006 ◽  
Author(s):  
LEI ZHANG ◽  
XUEJUAN ZHANG ◽  
HAO CHAI ◽  
YAOCAI LI ◽  
YONGJIE ZHOU
Keyword(s):  
Fractal Dimension ◽  
Pore Structure ◽  
Pore Size ◽  
Clay Mineral ◽  
Mineral Content ◽  
Fractal Theory ◽  
Average Pore Size ◽  
Structure Characterization ◽  
Imaging Method ◽  
Average Pore

Fractal dimension is an important parameter in the evaluation of tight reservoirs. For an outcrop section of the Nenjiang formation in the Songliao Basin, China, the pore structure and pore fractal characteristics of shale parasequences were investigated using fractal theory. In addition, factors causing pore structure changes were analyzed using the results of low-temperature nitrogen adsorption and scanning electron microscope (SEM) experiments. Conducive to gas migration and secondary pores development such as dissolution, results showed that nanoscale pores dominated by fracture-like morphology and consequent good internal connectivity were observed in each pore size section within the target layer. Each parasequence is characterized by a sequential upward decrease of average pore size and an upward increase of total pore volume, with an increasing number of pores from 2[Formula: see text]nm to 50[Formula: see text]nm. Pores are isolated from each other, with poor connectivity and relatively complex composition of brittle minerals and clay minerals. Main components of the brittle minerals, quartz and feldspar, occur in 20–50% and higher clay mineral content ranging from 50% to 70%. In the parasequence cycle, clay mineral gradually decreases while the brittle mineral content increases. Fractal dimension is negatively correlated with clay mineral content and positively correlated with brittle mineral (quartz and feldspar) content. The fractal dimension calculated by the imaging method and the FHH method shows an upward increasing tendency in each of the parasequence cycles. This is as a result of different phenomena, varied sediment hydrodynamic forces leading to particle size differences and increased brittle minerals resulting in microcracks, therefore, the fractal dimension of the large pores (imaging method) increases upward in the parasequence. Simultaneously, with increased content and accompanied dissolution of brittle minerals causing an increase of small pores from base to top of the parasequence, the fractal dimension of the small pores (FHH method) grows.

Quantitative evaluation of mineral admixtures on the properties, pore structure, and durability of cement-based composites

2012 ◽  
Vol 19 (2) ◽  
pp. 199-207 ◽  
Author(s):  
Chinlai Lee ◽  
Maochieh Chi ◽  
Ran Huang
Keyword(s):  
Fly Ash ◽  
Pore Structure ◽  
Silica Fume ◽  
Mercury Intrusion Porosimetry ◽  
Cementitious Material ◽  
Mineral Admixtures ◽  
Penetration Test ◽  
Compressive Strength Test ◽  
Testing Data ◽  
Influence Of Water

AbstractThe influence of water/cementitious material ratio, silica fume, and fly ash as partial Portland cement replacement materials on the properties, pore structure, and durability of cement-based composites was evaluated by conducting compressive strength test, mercury intrusion porosimetry test, water absorption, rapid chloride penetration test, and scanning electron microscopy (SEM). Water/cementitious material ratio, and replacement percentage of silica fume and fly ash have significant effects on the pore structure and durability of cement-based composites. Composites with silica fume or fly ash have a denser structure than the control composite on SEM micrographs. Silica fume has about 5–10 times as much effect as fly ash, according to results of multiple linear regression analyses of testing data.

The Effect of the Freeze-Thaw Cycles in Nanometer Pores on the Cement Structure

2014 ◽  
Vol 488-489 ◽  
pp. 620-624
Author(s):  
Long Zhou ◽  
Xu Liang Hou ◽  
Zhong Ping Wang
Keyword(s):  
Pore Structure ◽  
Pore Size ◽  
Average Pore Size ◽  
Pore Wall ◽  
Average Pore ◽  
Freeze Thaw ◽  
Changing Trends ◽  
Bet Method ◽  
Resistance Durability ◽  
20 Nm

The pore structure of cement-based materials is closely related to the freeze-thaw resistance durability. And this paper focused on nanometer pores to verify the connection of freeze-thaw cycles in the nanometer pores with the structure deterioration and to explore the stress in the pore wall during the freeze-thaw process. And BET method was adopted to analyze the pore structure of the cement and results indicated the changing trends of parameters such as the pore volume, average pore size and surface area of specimens. Moreover, pore size distribution presented prominent fluctuations of pore sizes in the range of 0 ~ 20 nm, while the changes on the scale of 20 ~ 100 nm were limited.

Development of a Collagen-Gag Copolymer Implant for the Study of Tendon Regeneration

1993 ◽  
Vol 331 ◽  
Author(s):  
L. K. Louie ◽  
I. V. Yannas ◽  
M. Spector
Keyword(s):  
Pore Structure ◽  
Pore Size ◽  
Average Pore Size ◽  
Scar Tissue ◽  
Silicone Elastomer ◽  
Pore Channel ◽  
Average Pore ◽  
Pore Sizes ◽  
Tendon Regeneration ◽  
Channel Orientation

AbstractFollowing injuries resulting in a gap, tendons generally do not heal sufficiently because the defect does not fill with reparative tissue, or the resulting scar tissue is not functionally adequate. The objective of this study was to engineer a collagen-GAG (CG) copolymer to facilitate tendon regeneration. Previous work in our laboratory using similar porous resorbable analogs of extracellular matrix have led to regeneration of skin and peripheral nerve.Matrices with controlled pore structure were produced by adapting the manufacturing technique developed in our laboratory for grafts with cylindrical geometry. CG suspensions contained within silicone elastomer tubes were frozen and lyophilized in a controlled manner. Quantitative optical microscopy was used to determine the percent porosity, average pore size, and pore orientation of the matrices.The CG matrices, formed in silicone elastomer tubes, 3.8 mm in diameter, had average pore sizes ranging from 20 to 150 μm. his range of pore sizes was comparable to that obtained previously using a diameter of 1.5 mm.1 The average pore size did not appear to be strongly dependent on the tubing diameter. The homogeneity of the pore structure and the pore channel orientation could be controlled by adjusting the temperature of the bath used for freezing the CG suspension and the velocity with which the graft was immersed into the coolant bath.

Effect of Heat-Treatment in Ar Atmosphere on Pore Structure of Carbonaceous Materials from Polysiloxane

2014 ◽  
Vol 602-603 ◽  
pp. 279-284
Author(s):  
Li Qun Duan ◽  
Chen Chen Zhang ◽  
Qing Song Ma ◽  
Zhao Hui Chen
Keyword(s):  
Heat Treatment ◽  
Pore Structure ◽  
Pore Size ◽  
Pore Volume ◽  
Average Pore Size ◽  
Total Pore Volume ◽  
Treatment Temperature ◽  
Carbonaceous Materials ◽  
Average Pore ◽  
Pore Size Distributions

Nanoporous carbonaceous materials derived from polysiloxane were first prepared by pyrolysis at 1300°C followed with hydrofluoric acid (HF) etching treatment. Their thermal stability of pore structure in inert condition was investigated in this paper by nitrogen adsorption technique in detail. The specific surface area (SSA) and pore volume (total pore volume, micropore volume, mesopore volume) decreased continually in the heat-treatment temperature range of 1000~1400°C. The average pore size almost kept the same with the raw sample. However, when the temperature exceeded 1400°C, the micropore interconnection began transforming to mesopore structure, which led to the decline of SSA and the increase of average pore size. Furthermore, the pore size distributions (PSDs) curves showed that heat-treatment had an advantage on the transition process of pore structure from disorder to regularity to some extent when heat-treated in the range 1000~1400°C for the most possible reason of relief of residue strain in the carbonaceous materials.

Evolution and Simulation of Pore Structure during the Calcinations of Limestone Pellets

2014 ◽  
Vol 1033-1034 ◽  
pp. 481-485
Author(s):  
Ming Chun Li ◽  
Jin Zhang ◽  
Zi Yao Yuan
Keyword(s):  
Pore Structure ◽  
Average Pore Size ◽  
Effective Diffusion ◽  
Nitrogen Adsorption ◽  
Bimodal Distribution ◽  
Gaseous Product ◽  
Diffusion Resistance ◽  
Fractional Conversion ◽  
Adsorption Method ◽  
Average Pore

The evolution characteristics of pore structure during the decomposition of limestone were experimental measured with nitrogen adsorption method. As a result, the pore structure of calcined limestone has a characteristic of bimodal distribution and the most probable pore sizes are about 3.8nm and 45nm. The probability ratio between the front and following humps decreases at first with the solid fractional conversion and then increases in the later stage of decomposition, and the corresponding inflection point of solid fractional conversion is aboutη=0.56 under the condition of calcination temperature 1133K. A probability density function with bimodal distribution for pore volume was established to construct the pore structure parameters model. As the average pore size decreased from 38.2nm to14.9nm, the effective diffusion coefficient of gaseous product through the porous solid product layer reduced from 0.0088cm2.s-1to 0.0017cm2.s-1, which leads to an increase in the pore diffusion resistance affecting the decomposition mechanisms of limestone.

Pore Structure and Sorption Properties of Silica Aerogels Studied by Magnetic Resonance Imaging and Pulsed-Field Gradient Spectroscopy

2003 ◽  
Vol 57 (3) ◽  
pp. 245-250 ◽  
Author(s):  
D. M. Gregory ◽  
R. E. Botto
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Pore Structure ◽  
Field Gradient ◽  
Average Pore Size ◽  
Mean Free Path ◽  
Resonance Imaging ◽  
Average Pore ◽  
Pulsed Field ◽  
Magnetic Resonance Imaging Mri

Magnetic resonance imaging (MRI) has provided direct visualization of gaseous xenon and methane in the void spaces of aerogels, offering unique information and insights into the pore structure and molecular diffusivities of occluded sorbates. Nuclear magnetic resonance (NMR) pulsed-field gradient (PFG) techniques were used to characterize exchange and diffusive motion of sorbed xenon gas at equilibrium. PFG measurements showed evidence of anisotropic diffusion; nominal self-diffusivity coefficients of xenon on the order of D = 10−7 m2/s were determined. Based on a mathematical relationship for the restricted diffusion of gases in confined environments, an expression for estimating the mean free path was derived, from which the average pore size could be obtained from the extrapolated value of the diffusion coefficient to low xenon pressures.

Influence Mechanism of Complex Admixtures on Chloride Diffusion Coefficient of C50 Self-Compacting Concrete for Marine Environment

2013 ◽  
Vol 312 ◽  
pp. 830-834
Author(s):  
Peng Ping Li ◽  
Zhi Hong Fan ◽  
Jian Bo Xiong
Keyword(s):  
Diffusion Coefficient ◽  
Fly Ash ◽  
Pore Size ◽  
Average Pore Size ◽  
Ash Content ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Self Compacting Concrete ◽  
Average Pore ◽  
Influence Mechanism

The influence of complex admixture on chloride diffusion coefficient of C50 self-compacting concrete for marine environment was investigated by means of the NT BUILD 443 Test, and the influence mechanism of complex admixture on the diffusion coefficient was studied, respectively. The results showed that the chloride diffusion coefficient decreased first and then increased with increasing the fly ash content in complex cementitious, and when fly ash content was 10% or 20%, it got the lowest value at 28 days or 90 days, respectively. Its more helpful to promote the fly hydration degree for extending curing period. Furthermore, the porosity and average pore size decreased first but then increased with increasing the fly ash content in complex cementitious, the porosity and average pore size got the lowest value when the fly ash content was 20% in cementitous.

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