Pore size distribution of portland cement slurries at very early stages of hydration (influence of curing temperature and pressure)

1984 ◽  
Vol 14 (3) ◽  
pp. 419-430 ◽  
Author(s):  
P. Parcevaux
Keyword(s):  
Portland Cement ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Curing Temperature ◽  
Early Stages ◽  
Temperature And Pressure

Preparation and Mechanism of Interconnected Mesoporous Carbon Monoliths from Phenolic Resin/Ethylene Glycol Mixtures

2012 ◽  
Vol 512-515 ◽  
pp. 403-406 ◽  
Author(s):  
Gang Zhang ◽  
Ze Wen Xiao ◽  
Guan Jun Qiao
Keyword(s):  
Phase Separation ◽  
Ethylene Glycol ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Mesoporous Carbon ◽  
Phenolic Resin ◽  
Fractal Dimensions ◽  
Mesoporous Structure ◽  
Curing Temperature

The preparation of interconnected mesoporous carbon monoliths (MCMs) derived from phenolic resin/ethylene glycol mixtures based on polymerization-induced phase separation have been investigated for fabrication of complex-shape SiC ceramics. The effect of the ethylene glycol content, curing catalyst and the curing temperature on the pore structure and pore distribution of carbon monoliths has also been studied, with emphasis on controlling the apparent porosity and pore size distribution. Fractal dimensions (DF) was proposed to evaluate the morphologies of carbon monoliths by using the box counting method. The results show that interconnected mesoporous carbon monoliths with narrow pore size distribution were obtained by changing the curing temperature and the content of ethylene glycol, curing catalyst in the resin mixtures and its mechanism was discussed in this paper. In this paper, interconnected mesoporous structure was attributed to the mechanism of spinodal decomposition (SD), which was discussed in detail. Carbon monoliths inherit their porosity from cured resins where it was formed as a result of phase separation of resin-rich and glycol- rich phases.

Macroporous Thermosets via Chemically Induced Phase Separation

1996 ◽  
Vol 431 ◽  
Author(s):  
J. Kiefer ◽  
R. Porouchani ◽  
D. Mendels ◽  
J. B. Ferrer ◽  
C. Fond ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Phase Separation ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
New Technology ◽  
Curing Temperature ◽  
Low Molecular Weight ◽  
Closed Cell ◽  
Chemically Induced

AbstractWe have explored a new technology based on chemically induced phase separation that yields porous epoxies and cyanurates with a closed cell morphology and micrometer sized pores with a narrow pore size distribution. When the precursor monomers are cured in the presence of a low molecular weight liquid, the desired morphology results from a phase separation and a chemical quench. After phase separation, the porosity is achieved by thermal removal of the secondary liquid phase, specifically by diffusion through the crosslinked matrix. In respect to the thermodynamics and kinetics, the origin of the phase separation process can be identified as nucleation and growth. The influence of internal and external reaction parameters, such as chemical nature of the low molecular weight liquid, its concentration and the curing temperature on the final morphology are presented. Thus, the morphology can be controlled ranging from a monomodal to bimodal pore size distribution with pore sizes inbetween 1 to 10 μm. These porous thermosets are characterized by a significantly lower density, without any loss in thermal stability compared to the neat matrix. Such new materials demonstrate great interest for lowering the dielectric constant and for improving the fundamental understanding of the role of voids in stress relaxation and toughening.

Chloride Permeability Of Concrete Containing A Flyash And A Blastfurnace Slag

1988 ◽  
Vol 137 ◽  
Author(s):  
Mitsunori Kawamura ◽  
Kazuyuki Torii
Keyword(s):  
Portland Cement ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Mercury Intrusion Porosimetry ◽  
Chloride Permeability ◽  
Curing Conditions ◽  
Mercury Intrusion ◽  
Blastfurnace Slag ◽  
Low Humidity

AbstractThe effects of curing conditions on the chloride permeability of concrete with various replacements of Portland cement by a flyash and a blastfurnace slag was investigated. In order to relate the porosity and pore size distribution of concretes to their chloride permeability, mercury intrusion porosimetry measurements were also conducted. The results showed that exposure of concretes to a relatively low humidity at early ages increased their chloride permeability. It was also found that the chloride permeability of concrete increased proportionally with increasing volume of pores larger than 0.1 μm in diameter.

Pore Structure Of Hydrated Cement Determined By Mercury Porosimetry And Nitrogen Sorption Techniques.

1988 ◽  
Vol 137 ◽  
Author(s):  
Yahia Abdel-Jawad ◽  
Will Hansen
Keyword(s):  
Pore Structure ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Pore Volume ◽  
Mercury Porosimetry ◽  
Total Pore Volume ◽  
Curing Temperature ◽  
Vycor Glass ◽  
Degree Of Hydration

AbstractThe pore structure (i.e. total pore volume, surface area and pore-size distribution curves) was measured using mercury porosimetry and nitrogen sorption. Hydrated portland cement (type I) of water-cement (w/c) ratios 0.3, 0.4 and 0.6 by weight was analyzed at three degrees of hydration (i.e., 30%, 50% and 80%; 70% for the 0.3 w/c system) corresponding to low, intermediate and high levels of hydration. The effect of curing temperature (3°, 23°, and 43°C) on pore structure was also studied. The two techniques were evaluated as well on porous Vycor glass, which has a narrow pore size distribution in the size range accessible to both. Results obtained by both techniques on porous Vycor glass agreed well. However neither technique can be used alone to study the entire pore structure in well-hydrated cement due to the wide range in pore sizes and the presence of micropores. Due to the unstable pore structure in cement a specimen treatment procedure such as methanol replacement, combined with volume-thickness (V-t) analysis, is necessary in order to measure the micropores. At low hydration values the pore structure can be estimated by mercury intrusion porosimetry (MIP). At higher hydration values, however, this technique underestimates total pore volume and surface area due to the presence of micropores which MIP cannot determine. In the pore size range of overlap, higher pore volumes were obtained with MIP. Nitrogen V-t analysis shows that micropores are more pronounced with lower w/c ratios. This finding is consistent with pore size distribution curves obtained by MIP. For a given w/c ratio and degree of hydration the total pore volume measured by MIP was found to be independent of curing temperature in the temperature range studied. At any w/c ratio, capillary porosity is controlled by degree of hydration alone.

Production of SiC Materials by Reactive Infiltration

2014 ◽  
Vol 783-786 ◽  
pp. 1863-1866 ◽  
Author(s):  
Mario Caccia ◽  
Javier Narciso
Keyword(s):  
Pore Size Distribution ◽  
Pore Size ◽  
Optical Microscopy ◽  
Size Distribution ◽  
Mercury Porosimetry ◽  
Density Measurement ◽  
Carbon Precursor ◽  
Reactive Infiltration ◽  
Temperature And Pressure ◽  
Porous Sic

The use of oak sawdust as carbon precursor for SiC manufacture via reactive infiltration was studied. The effect of oak sawdust pressing parameters, temperature and pressure, on the final SiC's properties was studied. Final product's quality was evaluated through density measurement, and microstructure and pore size distribution variations were characterized with optical microscopy and mercury porosimetry. Pressed oak sawdust preforms were carbonized to obtain a carbon porous preform which was then infiltrated with melted silicon. Successful infiltration of preforms pressed at room temperatures were performed, to obtain a porous SiC. Hot pressed preforms were not satisfactory infiltrated due to a narrowing of their pores caused by SiC formation's expansiveness.

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.

Sign in / Sign up

Export Citation Format

Share Document