Mean Spacing of Air Voids in Hardened Concrete

10.14359/4016 ◽  
1993 ◽  
Vol 90 (2) ◽  
Keyword(s):  
Hardened Concrete ◽  
Air Voids

scholarly journals The Effect of Fly Ash Microspheres on the Pore Structure of Concrete

Minerals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 58 ◽  
Author(s):  
Elzbieta Haustein ◽  
Aleksandra Kuryłowicz-Cudowska
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Total Content ◽  
Spherical Particles ◽  
Hardened Concrete ◽  
Image Analysis System ◽  
Micro Computed Tomography ◽  
Concrete Technology ◽  
Air Voids ◽  
X Ray

The fly ash microspheres (FAMs) formed during the mineral transformation stage in coal combustion are hollow spherical particles with a density less than water. This paper presents the results of X-ray micro-computed tomography and an automatic image analysis system of the porosity in the structure of hardened concrete with microspheres. Concrete mixtures with ordinary Portland cement and two substitution rates of cement by microspheres—5% and 10%—are investigated. For all considered mixes, a constant water/binder ratio (w/b) equal to 0.50 was used. The distribution of the air voids and the compressive strength of the concrete were tested after 28 days. With the increasing mass of cement replacement by FAMs, the compressive strength decreases after 28 days. The total volume of the air voids in hardened concrete with fly ash microspheres tested by X-ray varies from 5.1% to 7.4%. The closed pores constitute more than 80% of the total content of air pores. The study proves that the use of microspheres grains with specific dimensions has a significant impact on concrete porosity. Their application in concrete technology can be an alternative aeration solution for fresh concrete mixes and an effective method for utilization.

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.

Experimental Investigation on the Influence of Water-Cement Ratio on Air-Void Parameters of Cement Concrete

2013 ◽  
Vol 771 ◽  
pp. 29-33
Author(s):  
Jin Xi Zhang ◽  
Chao Wang ◽  
Ming Yang Guo ◽  
Mao Cheng Ma
Keyword(s):  
Experimental Investigation ◽  
Hardened Concrete ◽  
Cement Concrete ◽  
Marked Rise ◽  
Air Voids ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Influence Of Water ◽  
Air Void ◽  
The Impact

This paper studies the effect of water-cement ratio [w/ on the air-void parameters of cement concrete, which has a significant influence on the durability of concrete. Based on the experimental investigation, it is found that the impact on the air content of hardened concrete due to different water-cement ratio is not great. Test results also indicate that with the increase of water-cement ratio, the spacing factors also experienced a marked rise, and the mean diameters as well as the specific areas of air voids evidently increased or declined, respectively, which may lead to an adverse effect on the frost resistance of concrete.

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.

scholarly journals Effect of Ground Waste Glass Addition on the Strength and Durability of Low Strength Concrete Mixes

Materials ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 190 ◽  
Author(s):  
Robert Jurczak ◽  
Filip Szmatuła ◽  
Tomasz Rudnicki ◽  
Jacek Korentz
Keyword(s):  
Waste Glass ◽  
Hardened Concrete ◽  
Test Results ◽  
Freezing And Thawing ◽  
Glass Addition ◽  
Air Voids ◽  
Cement Ratio ◽  
Definition Of ◽  
Strength And Durability ◽  
Recycled Waste

By recycling used glass containers, we are able to recover and reuse their valuable properties, which is a way to preserve the relevant natural resources and lessen environmental burdens. For example, recycled waste glass (in the form of powder) can be used in the production of concrete. This article analyses the effect of waste glass addition on the properties of C12/15, which is used, for example, as concrete bedding material to support road drainage gutters and kerbs. Ground waste glass was used as a filler in the mix, i.e., without decreasing the amount of cement. Brown glass collected as municipal solid waste was used in this research. The research comprised an experiment prepared on the basis of the central composite design. The independent variables included water/cement ratio and the amount of glass powder, expressed as the glass to cement ratio by weight. The adopted research program mainly included the definition of the concrete compressive strength, water absorption and freeze–thaw resistance after 25 and 100 cycles of freezing and thawing. For selected systems, the characteristics of air voids in hardened concrete were also defined. The beneficial effect of ground waste glass added as a filler to the concrete mixture on the strength and durability of concrete was confirmed by the obtained test results.

scholarly journals The Effect of Steel and Polypropylene Fibers on the Properties of Horizontally Formed Concrete

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5827
Author(s):  
Adrian Chajec ◽  
Łukasz Sadowski
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Comparative Analysis ◽  
Fresh Concrete ◽  
Mechanical Analysis ◽  
Hardened Concrete ◽  
Polypropylene Fibers ◽  
Structural Concrete ◽  
Air Voids ◽  
The Impact

The article presents a comparative analysis of the impact of the addition of steel and polypropylene fibers on the properties of the concrete mixes and hardened concrete used in the concrete floor industry. The behavior of concrete intended for floors is different from conventional structural concrete because it is formed horizontally; until now, the effect of steel and polypropylene fibers on the properties of concrete formed horizontally has not yet been fully understood. Therefore, the aim of this article is to examine this issue and compare the behavior of concrete modified with steel and polypropylene fibers in concrete that is formed horizontally. The following properties of fresh concrete mixes were analyzed: consistency, the content of air-voids, and bulk density. Consequently, the following properties of hardened concrete were analyzed: compressive strength, bending tensile strength, and brittleness. It was confirmed that steel and polypropylene fibers have a different type of effect on the properties of fresh concrete mixes and hardened concrete. Finally, a combined economic and mechanical analysis was performed.

Sign in / Sign up

Export Citation Format

Share Document