scholarly journals Relationship between Pore Structure and Chloride Ion Diffusivity in Cementitious Materials

2018 ◽  
Author(s):  
Yuya Sakai
Keyword(s):  
Pore Structure ◽  
Cement Paste ◽  
Pore Diameter ◽  
Chloride Ion ◽  
Total Porosity ◽  
Cementitious Materials ◽  
The Other ◽  
Diffusion Test ◽  
Other Hand ◽  
And Diffusion

In this study, literature on pore structure and chloride ion diffusivity was collected to investigate the correlation of pore structure indicators with diffusivity. Good correlation between total porosity and chloride ion diffusivity was found when the samples did not contain admixture materials and diffusion test was conducted without acceleration. Pore diameter indicators did not correlate with diffusivity. The diffusivity of cement paste was reduced by admixture materials compared to that without admixture materials even if the total porosity is the same. On the other hand, the diffusivity of concrete was not reduced by admixture materials.

Influence of Pore Structure on Chloride Distribution in Surface Layer of Cement Paste under Cyclic Wet-Dry Condition

2018 ◽  
Vol 875 ◽  
pp. 165-173
Author(s):  
Hong Lei Chang ◽  
Song Mu ◽  
Ya Ya Du ◽  
Li Yang
Keyword(s):  
Surface Layer ◽  
Pore Structure ◽  
Cement Paste ◽  
Pore Diameter ◽  
Total Porosity ◽  
Chloride Content ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Chloride Profiles ◽  
Peak Value

This research focuses on influence of pore structure on chloride distribution in surface layer of cement paste under cyclic wet-dry condition. The results of chloride distribution reveal that drying and wetting cycles can lead to a peak value of chloride content (Cmax) occurring in surface layer of cement paste. Cmax increases with the increase of W/C. While the depth (Δx) at which Cmax appears does not show a regular change. Moreover, Cmax should be used to predict service life of concrete structures when Cmax appears in the chloride profiles. For the influence of pore structure, there exists an obvious hyperbolic relationship between chloride diffusion coefficient (D), Cmax and pore structure parameters. D and Cmax increase with total porosity and the most probable pore diameter, decrease with tortuosity, and stabilize gradually. And the most probable pore diameter has the most significant impact on D and Cmax. In addition, XRD and SEM-EDS results indicate that the deposition of Friedel’s salt results in the formation of more inkbottle shaped pores, which may cause the appearance of Cmax under cyclic drying-wetting conditions due to hysteretic moisture effect.

The Effect of Leaching on the Pore Structure of Cement-Based Grouts for Use in Nuclear Fuel Waste Disposal

1990 ◽  
Vol 212 ◽  
Author(s):  
M. Onofrei ◽  
M. N. Gray ◽  
D. Breton ◽  
G. Ballivy
Keyword(s):  
Pore Structure ◽  
Total Porosity ◽  
Cementitious Materials ◽  
X Ray ◽  
Diffusion Characteristics ◽  
Deep Geological Disposal ◽  
Porosity And Permeability ◽  
Nuclear Fuel Waste ◽  
And Diffusion

ABSTRACTResearch on the longevity of cement-based grout materials for sealing a deep geological disposal vault is an important aspect of the Canadian and other nuclear waste management programs. These studies include assessments of the chemical durability of cement grouts, and the effects of leaching and phase transformation on the long-term hydraulic and diffusion characteristics of grouts.This paper presents the results of laboratory studies carried out to assess the effects of leaching of cement phases on the pore structure of hardened grouts. Measurements of mercury intrusion and scanning electron microscopy with energy dispersive x-ray analysis, have been used to investigate the changes in pore structure of both a reference grout (90% Type 50 cement, 10% silica fume, water-to-cementitious materials ratio between 0.4 and 0.7) and ALOFIX-MC (a fine cement product of Japan), as a function of leaching time.The work discussed here reveals that the porosity of hardened grout does change during leaching, but within limits that depend on grout composition and initial porosity. The results confirm that the materials have the potential to self-seal and maintain their performance for longer periods than those currently predicted by longevity models.Our studies of the porosity and permeability of grouts suggest that pore size distribution rather than total porosity is the more important parameter in determining longevity.

Permeability of Lightweight Aggregate Concrete with Mineral Admixture

2013 ◽  
Vol 857 ◽  
pp. 105-109
Author(s):  
Xiu Hua Zheng ◽  
Shu Jie Song ◽  
Yong Quan Zhang
Keyword(s):  
Pore Structure ◽  
Lightweight Concrete ◽  
Chloride Ion ◽  
Lightweight Aggregate ◽  
Total Porosity ◽  
Normal Weight ◽  
Mineral Admixture ◽  
Mineral Admixtures ◽  
Lightweight Aggregate Concrete ◽  
Aggregate Concrete

This paper presents an experimental study on the permeability and the pore structure of lightweight concrete with fly ash, zeolite powder, or silica fume, in comparison to that of normal weight aggregate concrete. The results showed that the mineral admixtures can improve the anti-permeability performance of lightweight aggregate concrete, and mixed with compound mineral admixtures further more. The resistance to chloride-ion permeability of light weight concrete was higher than that of At the same strength grade, the anti-permeability performance of lightweight aggregate concrete is better than that of normal weight aggregate concrete. The anti-permeability performance of LC40 was similar to that of C60. Mineral admixtures can obviously improve the pore structure of lightweight aggregate concrete, the total porosity reduced while the pore size decreased.

The Influence of Pore Structure on the Properties of Cement Paste: Initial Observations about Research-in-progress

1988 ◽  
Vol 137 ◽  
Author(s):  
D. A. Lange ◽  
H. M. Jennings ◽  
S. P. Shah
Keyword(s):  
Pore Structure ◽  
Fracture Energy ◽  
Optical Microscopy ◽  
Cement Paste ◽  
Material Properties ◽  
Direct Method ◽  
Total Porosity ◽  
Pore Geometry ◽  
Method Of Measurement ◽  
A Direct Method

AbstractInitial observations of the influence of pore structure on material properties of cement paste are described. The total porosity is held constant and pore structure is altered by use of a superplasticizer. Corresponding changes in strength and fracture energy are observed. Changes in the cement paste pore structure are evaluated by analysis of images obtained by optical microscopy. The technique is a direct method of measurement that avoids assumptions about pore geometry.

The Influence of Pore-Strucrure on the Campressive Strength of Hardened Cement Paste

1984 ◽  
Vol 42 ◽  
Author(s):  
Huang Yiun-Yuan ◽  
Ding Wei ◽  
Lu Ping
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Pore Structure ◽  
Cement Paste ◽  
Total Porosity ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
New Information ◽  
The Relationship ◽  
Empirical Constants

AbstractThe pore-structure strongly influences the carpressive strength of hardened cement paste (hcp) and other porous materials, as well as other mechanical properties. The simplest but most currently used expression representing the relationship between the pore-structure and compressive strength is fram Balshin: σ = σ0 (l-P)A, in which only the total porosity P is involved as a single parameter and σ0 and A are empirical constants. The influence of pore size distribution and pore shapes etc. are not considered.The authors introduce second parameter w - the factor of relative specific surface area of the pores other than the total porosity P into consideration and a new expression is proposed:σc=K11-p/1+2p(K2(1-p))K3w+K4 all the constants K1 - K4 can be determined experimentally. By using of this expression the new information relating the influence of pore-structure on the caopressive strength of hcp can be predicted.

Frederick II of Hohenstaufen and Arabic Science

2001 ◽  
Vol 14 (1-2) ◽  
pp. 289-312 ◽  
Author(s):  
Matthias Schramm
Keyword(s):  
Biological Sciences ◽  
Scientific Knowledge ◽  
The Other ◽  
Political Practice ◽  
Unique Role ◽  
Other Hand ◽  
Court Life ◽  
The One ◽  
And Diffusion ◽  
Contemporary Approach

The article argues that Frederick II of Hohenstaufen and his court played a unique role in the transfer and diffusion of Arabic science (with its Greek, Hebrew and Christian elements). Scientists at the court translated and elaborated upon it. Moreover, there existed a two-way traffic of scientific knowledge between Frederick and his court scholars, on the one hand, and several oriental courts and their scientists on the other hand. Thus the reader gains a view of Frederick's scientific activities from the Arab perspective, too.Frederick's contribution to the existing biological sciences of his time was his “Book of Falconry”, which was exceptional in the then contemporary approach and methods employed in those fields. Even in this treatise on falconry, Frederick drew upon the fund of knowledge of Arab practitioners. This chain of arguments concerning Arabic science is situated within the setup of Frederick's oriental political practice and sumptuous court life.

Influence of Perlite Admixture on Pore Structure of Cement Paste

2010 ◽  
Vol 97-101 ◽  
pp. 552-555 ◽  
Author(s):  
Le Hua Yu ◽  
Hui Ou ◽  
S.X. Zhou
Keyword(s):  
Pore Structure ◽  
Cement Paste ◽  
Pore Diameter ◽  
Total Pore Volume ◽  
Hydration Reaction ◽  
Curing Time ◽  
Cement Pastes ◽  
Mercury Intrusion ◽  
Pore Surface Area ◽  
Strength And Durability

The parameters on pore structure of Portland cement pastes blended respectively with 0, 10, 20, 30 and 40% perlite admixture at 3，28，60 curing day were determined by Mercury Intrusion Porosimetre and presented in the paper to investigate affection on performance of cement-based material due to mix the admixture. The research results indicated that since the second hydration reaction had gone on with curing time, perlite admixture could diminish porosity, decrease pore diameter and reduce pore surface area in cement paste. Pores were gradually evolved from original small pores to later smaller pores, moreover fully filled with hydration products and disappeared during hydration reaction. So that the total pore volume in the paste was descended, and the proportion of harmless pores (gel pores and micropores) to whole pores was increased but that of harmful pores (macropores) subtracted. It is concluded that perlite admixture should help to increase the mechanical strength and durability of cement-based materials.

Relation Between Strength, Pore Structure and Associated Properties of Slag-Containing Cementitious Materials

1984 ◽  
Vol 42 ◽  
Author(s):  
Della M. Roy ◽  
G. M. Idorn
Keyword(s):  
Blast Furnace ◽  
Portland Cement ◽  
Pore Structure ◽  
Cement Paste ◽  
Blast Furnace Slag ◽  
Cementitious Materials ◽  
Granulated Blast Furnace Slag ◽  
Pore Structures ◽  
Furnace Slag

AbstractSubstantial increases of the strength of cement paste and mortars may be obtained in conventional processing by optimizing the materials components, the rheology and the curing, and thereby improving the microstructures. Cementitious materials with high proportions of granulated blast-furnace slag have been investigated. Higher strengths of ASTM C 109 mortars were obtained with 40 to 65% substitution of portland cement by slag, than with ordinary mix compositions and processing.For one set of mixtures, 28 day strengths ≥ 100 MPa (some as high as 240 MPa) were consistently attained after curing at temperatures ranging from 27 to 250°C. The slag substitutions developed finer pore structures as revealed by intrusion porosimetry measurements, than those with pure portland cement. This is believed to be a major reason for their enhanced durability. At each stage from 3 to 28 days, increase of curing temperatures from 27 to 90°C decreased porosity and increased the strength, reflecting an increased maturity.Implications for practice and suggestions for further work are discussed.

Effect of Red Mud on Mechanical Properties of Loess–Containing Aluminosilicate Based Cementitious Materials

2009 ◽  
Vol 610-613 ◽  
pp. 155-160
Author(s):  
Jian Hua Wan ◽  
Heng Hu Sun ◽  
Ying Ying Wang ◽  
Chao Li
Keyword(s):  
Mechanical Properties ◽  
Red Mud ◽  
Cementitious Materials ◽  
Cementitious Material ◽  
The Other ◽  
Term Strength ◽  
Other Hand ◽  
Early Strength ◽  
The One

The effect of the thermal treated red mud on mechanical properties of loess –containing aluminosilicate based cementitious materials is investigated. And the characteristic of hydration production is tested using XRD, SEM and EDAX methods. The results show that the thermal treated red mud not only has excellent cementitious properties but also can improve the mechanical properties of loess –containing aluminosilicate based cementitious materials. Moreover when the content of red mud is 5%, the improved effect is optimal. On the one hand, the alkaline ingredients of red mud can promote abundant ettringites to produce at early ages. And the ettringites contribute to early strength of the cementitious material. On the other hand, the content of red mud is too high to improve the long-term strength.

scholarly journals Correlations between Air Permeability Coefficients and Pore Structure Indicators of Cementitious Materials

2018 ◽  
Author(s):  
Yuya Sakai
Keyword(s):  
Pore Structure ◽  
Pore Volume ◽  
Percolation Theory ◽  
Permeability Coefficient ◽  
Pore Diameter ◽  
Total Pore Volume ◽  
Cementitious Materials ◽  
Air Permeability ◽  
Permeability Coefficients ◽  
Using Data

Correlations between the air permeability coefficient and various pore structure indicators in cementitious materials were examined to determine the pore structure indicator that best evaluated air permeability using data from previous studies of air permeabilities and pore structures. The determination coefficients of air permeability with total pore volume, critical pore diameter, and ordinary threshold pore diameter were low, although these have often been used as indicators. The median and threshold pore diameters obtained by percolation theory showed high determination coefficients. The equation using the threshold pore diameter better estimated the air permeability coefficient than the Katz–Thompson equation.

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