scholarly journals Development of the Measuring Techniques for Estimating the Air Void System Parameters in Concrete Using 2D Analysis Method

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 428
Author(s):  
Agnieszka Molendowska ◽  
Jerzy Wawrzeńczyk ◽  
Henryk Kowalczyk
Keyword(s):  
Concrete Surface ◽  
Equivalent Diameter ◽  
Air Voids ◽  
System Parameters ◽  
Air Content ◽  
Image Prior ◽  
Void System ◽  
Scanned Image ◽  
Air Void ◽  
The Impact

The purpose of the present study was to determine the impact of image quality on the results of air void system parameters determination in air-entrained concretes. The focus was on technical aspects related to the preparation of the scanned image of the concrete surface, which was then subjected to 2D surface analysis. Image processing aimed at separating joined voids and removing various types of defects in aggregate and cement mortar. The specific surface of the voids was determined with the air void equivalent diameter or perimeter as the calculation basis. Applying the Schwartz–Saltykov method, the 3D distribution of the air voids was reconstructed based on 2D measurements. On this basis, the micro-air content A300 was determined. The results of the 2D method were compared with the results of determinations carried out using the linear traverse (1D) method according to EN 480-11. The tests confirm the need to correct the image prior to measurements. Comparative tests showed good agreement between the air void system parameters determined using the 2D analysis and the EN 480-11 chord length counting method.

Effect of micro air void system on the permeability of latex-modified concretes with ordinary Portland and very early strength cements

2007 ◽  
Vol 34 (8) ◽  
pp. 895-901 ◽  
Author(s):  
K K Yun ◽  
D H Kim ◽  
K J Kim
Keyword(s):  
Image Analysis ◽  
Specific Surface ◽  
Average Distance ◽  
Chloride Permeability ◽  
Air Voids ◽  
Spacing Factor ◽  
Void System ◽  
Early Strength ◽  
Air Void ◽  
The Impact

This study focused on the impact of the micro air void system on the chloride permeability of latex-modified concretes with ordinary Portland and very early strength cements. The micro air void system was analyzed with the image analysis method. The results of this study will help field engineers and researchers gain a better understanding of the chloride permeability characteristics of latex-modified concretes. The results show that the latex-modified concretes made with both Portland and very early strength cements have more micro air voids, ranging 50 to 500 µm, than ordinary concretes. These small air voids decrease the spacing factor, which is defined as half the average distance that unstable water must travel to reach an escape boundary. The specific surface ranges from 8 to 27 mm–1 and the spacing factor ranges from 275 to 602 µm for ordinary Portland and very early strength cement concretes without and with latex modification. The specific surface tends to decrease as the spacing factor increases. The spacing factors of concretes tend to decrease with latex modification and with very early strength cement. It seems clear that the use of polymer latex in concrete can significantly lower the value of the air void spacing factor by entraining a large number of micro air voids (below 100 µm in diameter). Key words: latex-modified concrete (LMC), micro air void system, chloride permeability, image analysis.

Impact of Concrete Placing Method on Air Content, Air-Void System Parameters, and Freeze-Thaw Durability

1996 ◽  
Vol 1532 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Kenneth C. Hover ◽  
Roger J. Phares
Keyword(s):  
Fresh Concrete ◽  
Free Fall ◽  
Hardened Concrete ◽  
Freezing And Thawing ◽  
Freeze Thaw ◽  
System Parameters ◽  
Air Content ◽  
Void System ◽  
Parking Lot ◽  
Air Void

Approximately 76 m3 (100 yd3) of ready-mixed, air-entrained concrete were placed in a parking lot and driveway at the Schwing America Manufacturing facility in White Bear, Minnesota, on June 21, 1994. This concrete was placed by means of a pump, crane and bucket, and truck-mounted conveyor, and came directly from the chute of ready-mix trucks. Pump configurations were used that allowed unrestricted free-fall of the concrete; a kink in the rubber hose at the end of the line created a slight back pressure and slowed the descent of the concrete. After placement, the concrete was consolidated by an immersion vibrator in some locations and struck off with no further consolidation in other locations. Air content of the fresh concrete was measured by ASTM C231 pressure meters at the truck chutes and at the point of placement. Air content and air-void system parameters of the hardened concrete were determined in accordance with ASTM C457. Actual freeze-thaw performance was evaluated by ASTM C666 for concrete sampled from the truck chute and sampled from the pavement after placement by the various methods. Twenty-four tests of the air content of concrete from six successive truckloads of concrete showed that the variation in truck-to-truck air content was frequently greater than the within-truck variation because of different methods of handling the concrete. Tests of the fresh concrete after pumping, conveying, chuting, and free-fall from the concrete bucket showed reduced air content. From analysis of the hardened concrete, it was observed that the air bubbles remaining in the pumped concrete were smaller than in the concrete as delivered. The air-void spacing factor was not significantly altered by pumping. In ASTM C666 freezing and thawing tests, the specimen experiencing the greatest loss of air content as a result of pumping was determined to have the lowest total air content of all specimens tested (before vibration), yet had the highest durability of all specimens tested.

scholarly journals Environmental Assessment of Frost-resistant Concrete with Superabsorbent Polymers

2020 ◽  
Vol 63 (2) ◽  
pp. 43-62
Author(s):  
Gui Li ◽  
Marianne Tange Hasholt ◽  
Ole Mejlhede Jensen
Keyword(s):  
Environmental Impact ◽  
Concrete Strength ◽  
Significant Loss ◽  
Strength Increase ◽  
Life Cycle Assessment Methodology ◽  
Void System ◽  
Strength And Durability ◽  
Air Entraining Agents ◽  
Air Void ◽  
The Impact

AbstractAir-entraining agents (AEA) are normally used to improve the frost resistance of concrete. However, it is not possible to accurately control the air void system in concrete with AEA. Thus, a significant loss of concrete strength is caused by over-dosing voids, and this increases the environmental impact from concrete structures. Superabsorbent polymer (SAP) can also be used to produce frost-resistant concrete. Compared to AEA, it can be used to precisely engineer the air void structure of concrete, promote cement hydration, and mitigate self-desiccation cracks. In this study, life cycle assessment methodology is applied to evaluate the overall environmental impact of frost-resistant concrete based on AEA and SAP, respectively. The results illustrate that frost-resistant concrete with SAP has a lower environmental impact than frost-resistant concrete with AEA if the strength and durability of concrete are considered in the defined functional unit. In addition, frost-resistant concrete with SAP reduces the environmental burdens of the vertical elements such as columns, but it increases the environmental load of the horizontal elements such as slabs, where the strength increase cannot be utilized. Moreover, the inventory data for AEA and SAP can affect the impact assessment results.

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.

Precision of the air void characteristics measurement by ASTM C 457: results of an interlaboratory test program

1996 ◽  
Vol 23 (5) ◽  
pp. 1118-1128 ◽  
Author(s):  
François Saucier ◽  
Richard Pleau ◽  
Daniel Vézina
Keyword(s):  
Test Method ◽  
Interlaboratory Study ◽  
Hardened Concrete ◽  
Probability Of Error ◽  
Air Content ◽  
Spacing Factor ◽  
Interlaboratory Test ◽  
Void System ◽  
Concrete Production ◽  
Air Void

Since 1993, the Quebec Department of Transportation requires all its concrete suppliers to demonstrate that their concrete satisfies the requirements of the CSA A23.1 standard as regards the maximum spacing factor of the air void system. This new requirement raises questions about the reproducibility of the ASTM C 457 test method. An interlaboratory study was carried out to verify if the variability of the test method is sufficiently low to allow reliable decisions on the acceptance or rejection of in-place hardened concrete. A total of 18 operators from 13 different laboratories microscopically examined the six concrete slabs used for the study. It is concluded that the average reproducibility coefficient of variation is 14.4% for the total air content measurement and 14.2% for the spacing factor measurement. Considering these results, the probability that the measured value of the spacing factor exceeds the mandatory limit of 230 μm on a concrete production containing an air void system with a spacing factor of 170 μm (the target value proposed in the CSA A23.1 M-94 standard) is less than 0.7% (a probability of error of about 1%, 5%, or 10% is typical of most quality control test methods). Key words: concrete, air content, air void measurement, spacing factor, ASTM C 457 standard, interlaboratory study, freeze–thaw durability.

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 Image-based Restoration of the Concrete Void System Using 2D-to-3D Unfolding Technique

2020 ◽  
Author(s):  
Yu Song ◽  
Chuanyue Shen ◽  
Robbie Damiani ◽  
David Lange
Keyword(s):  
Air Entrainment ◽  
Void Size ◽  
Essential Information ◽  
Air Voids ◽  
Freeze Thaw ◽  
Void System ◽  
Void Structure ◽  
Unfolding Analysis ◽  
Air Void ◽  
2D To 3D

Hardened air void analysis provides essential information of concrete freeze-thaw durability based on the size and spacing of air voids in the material. As the physical freeze-thaw experiment is time-consuming and costly, the characteristics of concrete air voids are often deemed as a proxy of the freeze-thaw performance. This analysis is typically done by measuring the 2D air void intersections on polished samples, but the current interpretation of the 2D void characters does not accurately represent the actual void structure in 3D. To solve this problem, a 2D-to-3D unfolding technique has been proposed in the field of stereology. However, the unfolding analysis is known to be sensitive to several factors, such as void population and size along with a binning scheme, where improper unfolding can considerably bias the prediction of the actual concrete void system. This study investigates the optimal strategy of conducting the unfolding analysis for concrete. The investigation is carried out on both idealized void systems to interrogate the influence of the critical factors individually, and real concrete samples with varying levels of air entrainment to assess the concrete-specific impacts. The concrete void system is studied based on a stereological model emulating the intersected 3D air voids on the surface of polished concrete. The results highlight that, for unfolding concrete voids, logarithmic binning scheme is far more accurate to linear binning. The low unfolding error of the concrete samples indicates that the proposed methodology enables an accurate restoration of 3D void size distribution.

Béton produit en bétonnière mobile et en usine conventionnelle : comparaison des caractéristiques du réseau de bulles d'air

1988 ◽  
Vol 15 (3) ◽  
pp. 306-314
Author(s):  
Gaston Larose ◽  
Michel Pigeon
Keyword(s):  
Key Words ◽  
Laboratory Tests ◽  
Fresh Concrete ◽  
Mobile Unit ◽  
Freeze Thaw ◽  
Air Content ◽  
Spacing Factor ◽  
Void System ◽  
Concrete Mixer ◽  
Air Void

The durability of concrete to freeze-thaw cycles is dependent upon the existence of an adequate air-void system. There are very few studies on the air-void system of field concretes. Laboratory tests have proven that the air content measurement on the fresh concrete is not sufficient to judge the aptitude of the air-void system to protect the concrete from frost damage.This paper is a comparison of the air-void systems of field concretes produced in either a conventional plant or a mobile unit the use of which is becoming more and more frequent. The concretes produced in the conventional plant generally had sufficient air-void systems for air contents in the usual range (5–7%). The mobile unit showed that a slightly higher air content (8%) was needed to produce an adequate air-void system. Key words: concrete, mobile concrete-mixer, air-void systems, air-entraining agent, spacing factor, surface area, air content.

A laboratory investigation for potential durability of ready-mixed concrete retempered for air content and workability

1976 ◽  
Vol 3 (4) ◽  
pp. 570-577 ◽  
Author(s):  
B. W. Langan ◽  
M. A. Ward
Keyword(s):  
Compressive Strength ◽  
Laboratory Investigation ◽  
Hardened Concrete ◽  
Air Content ◽  
Spacing Factor ◽  
Void System ◽  
Air Void ◽  
Ready Mixed Concrete ◽  
Mixed Concrete

The effects of agitation and retempering on some properties of fresh and hardened concrete are considered.Data are presented on the influence of agitation and retempering with an air-entraining agent on the workability, compressive strength, and air void system in hardened concrete.The results indicate that although agitation reduces air content and increases the spacing factor, the original parameters can be regained by proper retempering. It is shown that any loss in compressive strength due to retempering is accompanied by an increase in potential durability due to the improvement of the air void system.

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