Effects of Strength, Permeability, and Air Void Parameters on Freezing-Thawing Resistance of Concrete with and without Air Entrainment

2010 ◽  
pp. 135-135-20 ◽  
Author(s):  
Gilson Lomboy ◽  
Kejin Wang
Keyword(s):  
Air Entrainment ◽  
Air Void

Air Entrainment and the Fabrication of Concrete Railroad Ties

2015 ◽  
Author(s):  
Mohammed T. Albahttiti ◽  
Ahmad A. Ghadban ◽  
Kyle A. Riding ◽  
David Lange
Keyword(s):  
Prestressed Concrete ◽  
Air Entrainment ◽  
Vibration Exposure ◽  
Vibration Acceleration ◽  
Manufacturing Plants ◽  
Air Content ◽  
Concrete Properties ◽  
Air Void

Handling and vibration can affect the air content of prestressed concrete railroad ties. The amount and variation in vibration experienced in concrete railroad ties were investigated to determine the concrete fabrication conditions typically used. Two methods of fabrication were investigated by measuring the concrete properties and vibration exposure during placement at two concrete tie manufacturing plants. In addition to measuring the vibration distribution in concrete railroad ties, a pair of ties were selected for hardened-air void analyses to determine any variation of air content in relation to the height of the ties. The vibration results indicate the existence of constructive and destructive wave-interferences in tie cavities. These interferences may contribute to large variations in the vibration acceleration throughout the length, depth, and width of concrete crossties during fabrication. This may account for the air-loss across the depth of the ties.

Influence de la température minimale du cycle de gel–dégel sur la détérioration du béton par écaillage en présence de sels fondants

1996 ◽  
Vol 23 (3) ◽  
pp. 595-601
Author(s):  
J. Marchand ◽  
M. Pigeon ◽  
L. Boisvert
Keyword(s):  
Test Procedure ◽  
Air Entrainment ◽  
Freezing Temperature ◽  
Freezing And Thawing ◽  
Concrete Mixtures ◽  
Conditioning Period ◽  
Binder Ratio ◽  
Freezing Cycle ◽  
Air Void ◽  
Scaling Resistance

Eight different concrete mixtures were prepared to investigate the influence of the minimum temperature of the freezing and thawing cycle on scaling deterioration due to deicer salt. In addition to the two minimum temperatures studied (−18 and −9 °C), test variables included the type of binder (with or without silica fume), the water/binder ratio (0.35 or 0.45), the characteristics of the air-void network (with or without air entrainment), and the drying temperature during the conditioning period prior to the scaling test (20, 40, or 110 °C). The scaling resistance to deicer salt of all concrete mixtures was assessed according to the prescriptions of the ASTM C672 test procedure using a 3 % NaCl solution. Test results indicate that a reduction of the minimal temperature from −9 to −18 °C significantly increases the scaling deterioration of concrete due to deicer salt. Key words: freezing cycle, scaling resistance, minimal freezing temperature, deicer salts.

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.

scholarly journals Scaling Resistance and Air Void Characteristics in Concrete Containing GGBS

2016 ◽  
Vol 62 (4) ◽  
pp. 181-192 ◽  
Author(s):  
J. Wawrzeńczyk ◽  
A. Molendowska ◽  
T. Juszczak
Keyword(s):  
Frost Resistance ◽  
Air Entrainment ◽  
Test Results ◽  
Fundamental Factor ◽  
Air Content ◽  
Concrete Mixtures ◽  
Spacing Factor ◽  
Void System ◽  
Surface Scaling ◽  
Air Void

AbstractIn this paper we discuss the test results for concretes containing various amounts of ggbs as compared to concretes made with Portland cement. The main objective of these tests is to evaluate the influence of varying air content in such mixtures on the structure and frost resistance of concrete. The authors suggest that the approach presented here allows for a safe design of concrete mixtures in terms of their frost resistance.The results indicate that concrete can be resistant to surface scaling even at the W/C ratio markedly higher than 0.45. Increased addition of ggbs leads to a decrease in concrete resistance to surface scaling. Proper air entrainment is the fundamental factor for frost-resistant concrete, and the air void system has to be assessed (micropore content A300, spacing factor $\overline L $). The addition of ggbs increases pore diameters, thus, to obtain the appropriate air pore spacing factor, micropore quantities introduced have to be increased.

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 Lower nappe aeration in smooth channels: experimental data and numerical simulation

2010 ◽  
Vol 82 (2) ◽  
pp. 521-537 ◽  
Author(s):  
Eudes J. Arantes ◽  
Rodrigo M. Porto ◽  
John S. Gulliver ◽  
Alberto C.M. Lima ◽  
Harry E. Schulz
Keyword(s):  
Void Ratio ◽  
Air Entrainment ◽  
Velocity Fields ◽  
Concentration Profiles ◽  
Dissolved Oxygen Concentration ◽  
Cfd Simulations ◽  
Pressure Profiles ◽  
Computational Fluid Dynamics Cfd ◽  
Air Void ◽  
Air Discharge

Bed aerators designed to increase air void ratio are used to prevent cavitation and related damages in spillways. Air entrained in spillway discharges also increases the dissolved oxygen concentration of the water, which can be important for the downstream fishery. This study considers results from a systematic series of measurements along the jet formed by a bed aerator, involving concentration profiles, pressure profiles, velocity fields and corresponding air discharges. The experimental results are, then, compared, with results of computational fluid dynamics (CFD) simulations with the aim of predicting the air discharge numerically. Comparisons with jet lengths and the air entrainment coefficients from the literature are also made. It is shown that numerical predictive tools furnish air discharges comparable to measured values. However, if more detailed predictions are desired, verification experiments are still necessary.

scholarly journals Effect of Low Atmospheric Pressure on Air Entrainment in Cement-Based Materials: An On-Site Experimental Study at Different Elevations

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 3975
Author(s):  
Xin Chen ◽  
Xu Liu ◽  
Bo Tian ◽  
Yong Ge ◽  
Lihui Li
Keyword(s):  
Experimental Study ◽  
Atmospheric Pressure ◽  
Raw Materials ◽  
Air Entrainment ◽  
High Elevation ◽  
Air Bubble ◽  
Air Content ◽  
Cement Based Materials ◽  
Low Atmospheric Pressure ◽  
Air Void

The efficiency and stability of air entrainment in concrete are sometimes found to be weaker at higher elevation. This phenomenon was attributed to the low atmospheric pressure by many researchers, however, the level of influence of atmospheric pressure on concrete air content dramatically varied among different studies. In order to clarify the effect of low atmospheric pressure on air entrainment in cement-based materials, an on-site experimental study was conducted with a rigorous control of irrelevant variables. The study focused on the air-entraining efficiency in cement paste, mortar, and concrete prepared in both low and standard atmospheric pressures. The air bubble stability in fresh mortar and air void characteristics of hardened mortar in different atmospheric pressures were also included. In the study, little effect of low atmospheric pressure on the air-entraining efficiency and air bubble stability in mortar with studied air-entraining agents (AEAs) was found. The air void characteristics were found to be similar between mortar with SJ-2 or 303R type AEAs prepared in different atmospheric pressures. Concrete with either SJ-2 or 303R type AEA prepared in low atmospheric pressure presented a satisfactory air content. These conclusions indicate that it is not necessary to worry excessively about the potentially adverse effect of atmospheric pressure on the frost resistance of concrete if a suitable AEA is applied. Additionally, a supplementary mortar study found that the low temperature of raw materials stored at high elevation would significantly weaken the air entrainment, reminding that potential causes in addition to low atmospheric pressure should also be taken seriously.

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.

Strength and durability of concretes containing 50% Portland cement replacement by fly ash and other materials

1990 ◽  
Vol 17 (1) ◽  
pp. 19-27 ◽  
Author(s):  
B. W. Langan ◽  
R. C. Joshi ◽  
M. A. Ward
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Portland Cement ◽  
Abrasion Resistance ◽  
Air Entrainment ◽  
Replacement Level ◽  
Freeze Thaw ◽  
Void System ◽  
Strength And Durability ◽  
Air Void

Results are presented from an investigation on the compressive strength and durability of concretes containing substitute materials at a 50% replacement level (by mass) of Portland cement. Seven fly ashes (sub-bituminous, bituminous, and lignitic), together with limestone and an inert material (silica flour), were used as replacement materials. Durability studies included freeze–thaw testing (ASTM C666A), scaling resistance (ASTM C672), and abrasion resistance (ASTM C944). The air void system was assessed using the modified point count method of ASTM C457. The results indicate that although concretes with a 50% replacement level of cementitious material did not perform as well as the control concretes with no replacement, such concretes were able to meet minimum durability requirements. As anticipated, air-entrainment is the overriding factor that allows concrete to meet freeze–thaw durability requirements. In the context of this study, compressive strength does not appear to be a significant factor in freeze–thaw durability. Results indicated that concretes with compressive strengths of less than 10 MPa will still pass the freeze–thaw test, provided an adequate air void system is in place. Abrasion resistance tends to increase with compressive strength but not in all the cases. Key words: concrete, fly ash, compressive strength, durability, mineral admixtures.

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