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Entrained Air Void Systems For Durable Highway Concrete
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Book Synopsis Entrained Air-void Systems for Durable Highway Concrete by : Peter Clement Taylor
Download or read book Entrained Air-void Systems for Durable Highway Concrete written by Peter Clement Taylor and published by . This book was released on 2021 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt: Laboratory testing and field experience have shown that highway concrete should be properly air entrained to resist the action of freezing and thawing, particularly in wet climates. Several gaps in the state of the knowledge still exist. The TRB National Cooperative Highway Research Program's NCHRP Research Report 961: Entrained Air-Void Systems for Durable Highway Concrete addresses these gaps and, more specifically, investigates innovative test methods for effectively characterizing the air system in fresh concrete and identifying the characteristics of the air-void system that are related to the performance of field concrete under freeze-thaw conditions. Appendices A -G provide further details on the different aspects of the research performed for this project.
Book Synopsis Entrained Air-Void System For Durable Highway Concrete by : Siamak Riyazi
Download or read book Entrained Air-Void System For Durable Highway Concrete written by Siamak Riyazi and published by . This book was released on 2020 with total page 199 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the US, the most commonly used F-T test method is AASHTO T 161 “A.” The equipment for variant A of the test is relatively low cost (~$22, 000) and compact. The relatively low cost stems from the basic construction of a refrigerant-based cooling system and resistive heating elements. These units are easily repaired by conventionally trained heating and air conditioning technicians and economically modified using readily available controls. Consequently, proposed factors and modifications to the test method are based on this piece of equipment. Sufficient background information exists in the research literature and current global applications to recommend improvements/modifications to the F-T test method, such as changes to the cooling rate, degree of saturation, and sample conditioning method. Based on an analysis of significant factors reported in the literature, in this study, a series of procedural and functional changes were proposed to better describe F-T durability as a function of the air void system. These changes include: 1- Procedural modifications including longer curing times to better encompass requirements for higher SCM mixtures and the introduction of a drying period to better simulate actual field exposure conditions, 2- Functional modifications including introducing water through capillary suction and changing the freezing solution to incorporate deicing salts, 3- A combination of modification approaches including application of a concentrated pre-storm brine followed by drying.The F-T research was performed in three phases. The first phase involved calibration and modification of the AASHTO T 161 “A” freeze-thaw cabinet using the proposed CDF-A procedure. A modification procedure was developed, and an appendix to the final report was described the steps taken to achieve the desired test requirements. The second phase involved evaluating three separate variants of the proposed test not encompassed by current test methods including the impact of curing time, deicer type, and deicer pretreatment. The third phase involved evaluating a wide range of concrete samples with varying levels and qualities of air systems.
Book Synopsis Enhanced Entrained Air Void System Characterization for Durable Highway Concrete by : Anthony Torres
Download or read book Enhanced Entrained Air Void System Characterization for Durable Highway Concrete written by Anthony Torres and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The air void system in concrete provides a strong influence on the behavior of cementitious materials in both the fresh and hardened state, especially as it relates to freeze-thaw resistance and deicer scaling. The most common test procedure to characterize the air void system is ASTM C457 – Standard Test method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete, which involves microscopic determination of the air content, paste content, air-void size distribution, and spatial dispersion of a sawn concrete sample. This procedure is reliant on the user to make hundreds of critical decisions per sample, which requires significant time, and is potentially subject to human error. Additionally, ASTM C457 provides minimal guidance regarding the exact steps and equipment necessary to prepare a sample for evaluation. The outcome of this research not only provides specific information regarding sample preparation for hardened concrete air void analysis, it also develops an alternative characterization technique that drastically minimizes evaluation time, human error, and increases reliability of key hardened air void characterization parameters. Specific results show on average air void difference of 0.5% and 0.7% between the alternative method versus ASTM C457 Procedure A and B, respectively. The results also show a significant reduction of analysis time from approximately 2 – 4 hours per sample to 15 minutes per sample when using the alternative method.
Book Synopsis Evaluating Air-entraining Admixtures for Highway Concrete by : Mohamad Nagi
Download or read book Evaluating Air-entraining Admixtures for Highway Concrete written by Mohamad Nagi and published by Transportation Research Board. This book was released on 2007 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This report presents a recommended procedure for evaluating air-entraining admixtures used in highway concrete. The procedure involves the testing of non-air-entrained concrete and concrete containing the air-entraining admixture under simulated field conditions. Criteria are proposed for acceptance of admixtures for use in either highway pavements or structures. The recommended procedure and acceptance criteria will guide materials engineers in evaluating and selecting air-entraining admixtures that should contribute to appropriate freeze-thaw durability and thus to good performance and long service life. The content of the report will be of immediate interest to materials engineers, researchers, and others concerned with the design of concrete mixtures for use in highway pavements and structures."--taken from Foreword, page [v].
Book Synopsis Control of Air Content in Concrete by : David Whiting
Download or read book Control of Air Content in Concrete written by David Whiting and published by Transportation Research Board National Research. This book was released on 1983 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Air-entrained Concrete by : National Research Council (U.S.). Highway Research Board
Download or read book Air-entrained Concrete written by National Research Council (U.S.). Highway Research Board and published by . This book was released on 1953 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: Paper 1: A method was developed which makes it possible to determine the characteristics of the entrained air voids in concrete. Briefly, the procedure consisted of cutting and polishing a section of concrete to expose the distributed voids. Paper 2: The performance record is described of 14 concrete test roads in five northeastern states. Built 10 to 14 years ago with a wide range of variables, these roads provide an opportunity to compare the performance of air-entrained concrete with adjacent sections of the same construction but without air entrainment.
Book Synopsis A Novel Approach to Characterize Entrained Air Content in Pervious Concrete by : J. T. Kevern
Download or read book A Novel Approach to Characterize Entrained Air Content in Pervious Concrete written by J. T. Kevern and published by . This book was released on 2008 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: The current pervious concrete placed in cold climates generally contains air entrainment but, unlike traditional concrete, the evaluation of entrained air is not performed. This paper presents results from a study that characterized the entrained air voids in pervious concrete using a RapidAir system. The RapidAir system is an automatic device that determines the air void properties of hardened concrete according to ASTM C457, "Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete." Two types of aggregates, i.e., crushed limestone and rounded river gravel (pea gravel), and two types of air entraining agents, i.e., natural and synthetic, were used. The air entrainment dosage rates varied from zero to double the manufacturer's recommended dosage. Compressive strength, tensile strength, and freeze-thaw durability (ASTM C666A) of the pervious concrete were tested. The results show that use of air entrainment improves workability of pervious concrete, thus reducing the overall porosity and increasing unit weight of the pervious concrete. The strength and freeze-thaw durability also increases with the level of entrained air in pervious concrete.
Book Synopsis Physical Factors Influencing Resistance of Concrete to Deicing Agents by : W. R. Malisch
Download or read book Physical Factors Influencing Resistance of Concrete to Deicing Agents written by W. R. Malisch and published by . This book was released on 1966 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt: Studies were made of the effects of varying concrete production methods upon potentially durable concrete. Variations in the surface porosity, strength and air void system produced by differing finishing techniques were evaluated for typical air-entrained concretes. Large and small scale specimens were cast and effects of period and time of finishing, environmental conditions, and additions of water during finishing were evaluated using surface scaling tests, surface tensile strength tests and microscopical determination of surface air void parameters. If a concrete is to remain durable when deicing agents are used, it must have proper air entrainment and curing.
Book Synopsis Distribution of Voids in Field Concrete by : Hamdi Celik Ozyildirim
Download or read book Distribution of Voids in Field Concrete written by Hamdi Celik Ozyildirim and published by . This book was released on 1978 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study was intended to evaluate the air void characteristics of concrete in an attempt to identify, quantitatively or semi-quantitatively, different types of voids and to predict their influence on strength and durability. At the outset, it was anticipated that total air contents and water-- cement ratios of concrete mixtures would reflect the presence of excess water or air voids. However, because it is difficult to determine the water-cement ratio of hardened concrete, an attempt was made to relate the water-cement ratio and the air content, taken as independent variables, to the parameters of the void system that are .readily determined from the hardened concrete. The parameters of the void system considered were 1. The specific surface and the spacing factor calculated from linear traverse data. 2. The constants of a continuous chord frequency distribution curve derived from a probability density function. 3. The mean diameters and the number of bubbles per unit volume determined by a graphical method. The concrete samples were prepared in the laboratory, and the variables included the amount of air entrainment, the water cement ratio, the mixing time, and the mixture temperature. The data on the void system were obtained by utilizing the chord lengths of voids determined by the linear traverse analysis of concrete specimens. Within the framework of the study it was not possible to correlate the combined effect of water and air content with the above mentioned void parameters. A good correlation was obtained between the air contents of fresh and hardened concretes that were properly measured. Satisfactory relationships were established between the measures of resistance to freezing and thawing (weight loss, relative dynamic modulus of elasticity, and the surface rating), and certain parameters-of the void system (the spacing factor, the specific surface, and the diameter of the bubbles).
Book Synopsis Field Study of Air Content Stability in the Slipform Paving Process by :
Download or read book Field Study of Air Content Stability in the Slipform Paving Process written by and published by . This book was released on 2012 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study evaluated the impacts of construction on the air content and air-void system structure of Portland cement concrete pavements. The primary intent was to quantify the air content of fresh concrete before and after it has gone through the slipform paver. The air-void system parameters of hardened concrete were then assessed using cast and extracted core specimens. The results of the air content testing on fresh concrete and the concrete cylinder specimens cast in the field suggested that there is some loss of air as the concrete passes through the paver. Laboratory testing performed on cores extracted from the pavement did not provide any conclusive evidence that entrained air is lost during the slipform paving process. In fact, many of the extracted cores had measured air content values that were much higher than the specification requirement. If excessive, this could result in increased permeability and low-strength related issues. Although a rigorous statistical analysis was not performed, the results suggest that the air content testing on fresh concrete is not capturing the true air content of the concrete placed with a slipform paver. The fresh concrete air content is generally lower than the air content measured in the cores.
Book Synopsis Manual on Control of Air Content in Concrete by : David Whiting
Download or read book Manual on Control of Air Content in Concrete written by David Whiting and published by . This book was released on 1998 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Laboratory Investigation of Air-void Systems Produced by Air-entraining Admixtures in Fresh and Hardened Mortar by : Daniel Stephen Lane
Download or read book Laboratory Investigation of Air-void Systems Produced by Air-entraining Admixtures in Fresh and Hardened Mortar written by Daniel Stephen Lane and published by . This book was released on 2006 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: The air-void systems produced by two commercially available air-entraining admixtures (AEA), one a vinsol resin formulation and the other a tall oil formulation, were studied in mortars. Mortars were composed of four different portland cements and two Class F fly ashes (20 percent by mass) with concrete sand. The mortar proportions were based on Virginia Department of Transportation Class A4 concrete with a water-cementitious material ratio of 0.45. Foam index tests were conducted on all cementitious combinations, and the results were used to determine the dosage of AEA in the mortars. The air content of the mortars was determined gravimetrically, and specimens were cast for subsequent linear traverse analysis of the air-void system. With both AEAs, mortar air contents in the target range produced spacing factors much lower than necessary to provide resistance to freezing and thawing, suggesting that the ranges for air content currently used in VDOT specifications could be reduced to lessen the potential for acceptance problems associated with excessive air content. Further study is recommended to verify that the relationships observed in this study are also observed in concrete and to define improved air content specifications.
Book Synopsis Techniques for Measuring Air Void Characteristics of Concrete by : Duane E. Amsler
Download or read book Techniques for Measuring Air Void Characteristics of Concrete written by Duane E. Amsler and published by . This book was released on 1973 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Effect of Entrapped Air on Air-void System Parameters in Hardened Concrete by : John T. Price
Download or read book The Effect of Entrapped Air on Air-void System Parameters in Hardened Concrete written by John T. Price and published by . This book was released on with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Effects of Boundary Conditions on the Air Void System of Air Entrained Concrete by : David F. Zawada
Download or read book The Effects of Boundary Conditions on the Air Void System of Air Entrained Concrete written by David F. Zawada and published by . This book was released on 1968 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Review of Literature on Air-entrained Concrete by : Patrick H. Torrans
Download or read book Review of Literature on Air-entrained Concrete written by Patrick H. Torrans and published by . This book was released on 1968 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Properties of Air Bubbles in Air Entrained Concrete by : Le Tuan Pham
Download or read book Properties of Air Bubbles in Air Entrained Concrete written by Le Tuan Pham and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is widely accepted that air entrainment, a purposeful introduction of small air bubbles in concrete, is critical to the long-term durability of concrete in freeze-thaw environments. Air entraining admixtures (AEA) are added to the mixture to stabilize air bubbles created during mixing, ensuring a proper air void system in the hardened concrete. Despite the complexity of creating a suitable air void system in concrete, previous study and experience established the reliability and robustness of such systems under a variety of conditions through use of neutralized vinsol resin (NVR) AEA products. In recent years, synthetic AEAs have been used more frequently due to limited supply of NVR to the concrete industry. With the use of synthetic AEAs, there are more reports of new problems including difficulties in accurately measuring the air content. This study was conducted to find the root cause of the increasing difficulties in controlling the air contents in portland cement concrete associated with synthetic AEAs. Main challenges included the lack of existing techniques to evaluate AEAs and air bubbles in concrete, and lack of data to help identify causes. Given these challenges, a multi-scale experimental study that included testing of field and laboratory concrete, and testing of foam and individual air bubbles was undertaken. The results indicate that the disparity between QC test results and the actual air contents in concrete pavements associated with the use of synthetic AEAs could be attributed to less robust air bubbles stabilized with synthetic AEAs compared to those entrained with NVR and the resulting increased loss of these air bubbles during concrete sampling. The cause of this decreased robustness and resulting air loss was traced directly to the properties of the bubble shells. The shells of air bubbles in concrete entrained with synthetic AEAs were thinner and less stiff than those associated with an NVR AEA. Through this research new test protocols were developed to measure stiffness and thickness of the shell of air bubbles extracted from cement paste and to quantify stability of foams of AEAs in a cementitious environment. These tests could be used by researchers and practitioners who are interested in developing new admixtures and/or identifying admixtures with undesirable performance.
