scholarly journals A Proposal of New Method for Determination of Radius Distribution of the Air Voids and Air Content in Hardened Concrete on the Basis of Probability Theory.

1997 ◽  
pp. 55-64
Author(s):  
Noriaki Iwasaki
Keyword(s):  
Probability Theory ◽  
New Method ◽  
Hardened Concrete ◽  
Air Voids ◽  
Air Content

Influence of Air Content and Vibration Time on Frost Resistance of Air Entrained Concrete

2013 ◽  
Vol 857 ◽  
pp. 110-115 ◽  
Author(s):  
Xiu Hua Zheng ◽  
Yong Ge ◽  
Jie Yuan
Keyword(s):  
Frost Resistance ◽  
Hardened Concrete ◽  
Air Voids ◽  
Air Content ◽  
High Durability ◽  
Void Structure ◽  
Vibration Time ◽  
Air Void ◽  
Air Void Structure ◽  
Air Entrained Concrete

Air-entraining agent turely is one of the necessary compositions of the high durability concrete. The influence of air content and vibration time on the frost resistance of concrete was researched, and air void characteristics of hardened concrete was analysed. The results showed that the air contents could reduce the compressive strengthof hardened concrete excessively, but it made the spacing factor reduce obviously and significantly improve the frost resistance of concrete.The air voids with different structure in concrete were realized by vibration time. It was found that the air void structure and the frost resistance properties were influenced by the vibration time largely. The optimized vibration time is 30s, the appropriate vibration time is 20s~30s, no more than 35s.

scholarly journals Characteristics of Entrained Air Voids in Hardened Concrete with the Method of Digital Image Analysis Coupled with Schwartz-Saltykov Conversion

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2439
Author(s):  
Teemu Ojala ◽  
Yanjuan Chen ◽  
Jouni Punkki ◽  
Fahim Al-Neshawy
Keyword(s):  
Image Analysis ◽  
Digital Image ◽  
Digital Image Analysis ◽  
Three Dimensional ◽  
Volume Density ◽  
Hardened Concrete ◽  
Air Voids ◽  
Air Content ◽  
Entrained Air ◽  
Number Of Classes

This paper presents the characteristics of air void systems in hardened concrete with the method of digital image analysis (DIA) coupled with Schwartz-Saltykov (SS) conversion. The results indicate that the DIA method coupled with SS conversion estimates the air content with more accuracy than it would without SS conversion; the correlation between air content obtained from the DIA method, and that from the thin section (TS) method is as good as the correlation observed between the pressure saturation (PS) method and the TS method. It was also found that the DIA method shows a better correlation with the TS method when the spacing factor without SS conversion is considered, while both methods show poor correlations when the corresponding specific surface is considered. In addition, it indicates that the peak of three-dimensional size distribution (3-DSD) of air voids after SS conversion falls in smaller voids, and 3-DSD of air voids shifts to a narrow size range, in comparison with the 2-DSD without SS conversion; the shape of the 3-DSD air voids remains constant irrespective of the class widths. Increasing the number of classes can minimise the standard deviation in the estimation, however, it also results in a leap in voids volume density, which will influence the estimation of air content.

The effect of foam fractionated lignosulphonates on air entrainment in concrete

1982 ◽  
Vol 9 (2) ◽  
pp. 170-175
Author(s):  
K. F. Keirstead ◽  
D. DeKee ◽  
D. W. Kirk ◽  
S. U. Pillai
Keyword(s):  
Surface Tension ◽  
Air Entrainment ◽  
Hardened Concrete ◽  
Air Voids ◽  
Air Content ◽  
Low Concentrations ◽  
Tension Properties ◽  
Air Entraining Agents ◽  
Air Void ◽  
Mixing Water

One of the properties of air-entraining admixtures that may influence their efficiency is their surface tension when combined with mixing water. Lignosol SF is a standard air-entraining agent. With the objective of identifying a product with improved qualities, Lignosol SF was fractionated and two of its fractions, respectively with low (foamate) and high (retentate) surface tension properties were investigated as potential air-entraining agents. Measurements were made both of air content in wet concrete mix and of the air-void characteristics of the hardened concrete.The results showed that at low concentrations and water:cement ratios the performance of all the three products above are similar. However, the foamate fraction becomes more effective in entraining air with increases in concentration and water:cement ratio. Further, this foamate resulted in the hardened concrete having bubbles with a smaller mean diameter than those in the retentate. The spacing factors for both these products were within recommended limits. Keywords: admixtures; air-entrainment; air-voids; concrete; freeze-thaw resistance; Lignosol; spacing factor.

Study of Correlation Relationships Aerated Concrete Intended for Waterproof Tunnel Lining

2014 ◽  
Vol 1054 ◽  
pp. 132-137 ◽  
Author(s):  
Adam Hubáček
Keyword(s):  
Czech Republic ◽  
Fresh Concrete ◽  
Tunnel Lining ◽  
Hardened Concrete ◽  
The Czech Republic ◽  
Air Content ◽  
Aerated Concrete ◽  
Durability Of Concrete

The paper focuses on the problems of concrete for watertight tunnel lining. The theme is currently quite topical in the Czech Republic and abroad. The accent is put particularly on determination of level of dependence of different parameters of aeration of fresh and hardened concrete (determined in accordance with standardized procedures in common use) and durability of the concrete based on observation of properties of aerated concrete. Fluctuation of values of air content in hardened and fresh concrete are observed as well as influence of this fluctuation on durability of concrete.

scholarly journals The Relationship between the Air Content in the Mortar and Concrete for Different Types of Cement

2019 ◽  
Author(s):  
Beata Łaźniewska-Piekar ◽  
Jacek Gołaszewski
Keyword(s):  
Cement Paste ◽  
Air Entrainment ◽  
Hardened Concrete ◽  
Test Results ◽  
Air Voids ◽  
Air Content ◽  
Air Volume ◽  
Spacing Factor ◽  
Different Types ◽  
The Relationship

Research results of the relationships between air-volume in air-entrained cement paste, mortar and concrete, all designed according to PN-EN 480-1 guidelines are presented in the paper. The cement paste, mortar and concrete, with w/c=0,5 ratio, were prepared using innovative air-entraining cement CEM II/B-V. The air-entraining cement CEM II/B-V was produced using two methods: mixed together with natural or synthetic aerated admixture. The air volume test of the volumetric method was carried out in case of fresh cement paste, mortar and concrete mix. Fresh concretes were evaluated in terms of stability of air entrainment and consistency for 5, 20 and 40 min. The porosity structure parameters, like summarized air-content, specific surface of air voids, air-voids spacing factor and micropores content of hardened concrete, were estimated using computed tomography with a resolution of 2-5 μm. The aim of the research was to determine the dependence between air-content of cement paste, mortar and concrete on the measurement of air-entrainment of cement paste or mortar with the same w/c ratio and type of cement, all designed according to PN-EN 480-1 guidelines. Test results proved that there is a good correlation between the measured air-content of the cement paste, mortar and concrete. Therefore, it is possible to predict the aeration of concrete on the air-entrainment of the mortar.

Determination of Parametres of the Air-Void System in Airfield Pavement Concrete Using Computed Tomography

2017 ◽  
Author(s):  
Danuta Kowalska ◽  
Paweł Iwanowski ◽  
Agata Kowalewska
Keyword(s):  
Computed Tomography ◽  
Air Entrainment ◽  
Image Resolution ◽  
Hardened Concrete ◽  
Polished Section ◽  
Air Voids ◽  
Tomography Method ◽  
Air Void ◽  
Pavement Concrete

Immediately after completion airfield pavements begin a gradual deterioration that is attribute to several factors. One of the major elements contribute to airfield pavement deterioration is exposure to the environment (freezingthawing and de-icing salts). Air-voids microstructure in cement-based materials is an important feature related to the freeze-thaw durability of these materials since all the adverse influences are result of potentially harmful ionic fluids and aggressive gas transport through the concrete and the transport properties strongly depend on the morphology of the pores inside the concrete. For revealing the porous microstructure in airfield pavement concrete X-ray tomography method was used. New and advance methodologies have been developed to determine the basic parameters of air entrainment in concrete (total content of the air, specific surface area of the air-voids system, spacing factor and content of micropores) by summing the distances traversed across a given component along a series of regularly spaced lines in one or more planes intersecting the sample. Using the method mentioned above, to meet requirements of PN-EN 480-11 specification (describes procedure for microscopical determination of air voids characteristics in hardened concrete), the original software was applied – AVCT (Air Void by Computed Tomography) computer programme. The specimens for CT testing were cylinders extracted by drilling out from the investigated concrete core or cubic specimen. The CT method does not require any special processing of the surface of tested specimen as opposed the common method according to PN-EN 480-11, by which the properly polished section is a prerequisite for obtaining proper results of air voids characterization. The paper presents the results of the evaluation of air-voids microstructure in concrete conducted with the application of computed tomography method. Exemplary images of distribution and size of air-voids in concrete specimens have been presented. Special attention was paid to obtain effective image resolution.

A new method for the determination of nitrates

1960 ◽  
Vol 23 ◽  
pp. 227-232 ◽  
Author(s):  
P WEST ◽  
G LYLES
Keyword(s):  
New Method

A New Method for the Determination of Plasma Activators of Fibrinolysis

1977 ◽  
Vol 37 (02) ◽  
pp. 210-215 ◽  
Author(s):  
R Margalit ◽  
E Gidron ◽  
Y Shalitin
Keyword(s):  
New Method ◽  
Effective Activator

SummaryThe term “effective activator” of plasminogen is proposed, to denote the resultant of activator-antiactivator interaction, and a method for the determination of the level of these activators is described. By adding axcess plasminogen to the euglobulin fraction of plasma the influence of the level of endogenous plasminogen and of the antiplasmin is eliminated. It is shown that the level of fibrinogen has very little bearing on the results. An effective activator unit is defined as equal to 1 CTA unit of urokinase activity on a fibrinogen-plasminogen substrate.

The Plasmin Inhibitors of Plasma

1964 ◽  
Vol 12 (01) ◽  
pp. 119-125 ◽  
Author(s):  
Y Shamash ◽  
A Rimon
Keyword(s):  
Human Plasma ◽  
New Method ◽  
Normal Amount ◽  
Caseinolytic Activity ◽  
Before And After ◽  
Plasmin Inhibitors

SummaryA new method for the assay of plasmin inhibitors in human plasma is described. The method consists of determination of the caseinolytic activity of a standard plasmin solution before and after incubation with the inhibitor, with lysine added to the mixture as a stabilizer of plasmin. Using this method, it was found that plasma contains enough inhibitors to inactivate 30 caseinolytic units of plasmin, or 10 times the normal amount of plasminogen in human plasma.

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