Entrained Air-void Systems for Durable Highway Concrete PDF Download
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Author: Peter Clement Taylor
Publisher:
ISBN: 9780309673723
Category : Air-entrained concrete
Languages : en
Pages : 72
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Book Description
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.
Author: Peter Clement Taylor
Publisher:
ISBN: 9780309673723
Category : Air-entrained concrete
Languages : en
Pages : 72
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Book Description
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.
Author: Anthony Torres
Publisher:
ISBN:
Category : Air-entrained concrete
Languages : en
Pages : 0
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Book Description
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.
Author: Siamak Riyazi
Publisher:
ISBN:
Category : Concrete
Languages : en
Pages : 199
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Book Description
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.
Author: Mohamad Nagi
Publisher: Transportation Research Board
ISBN: 0309098890
Category : Air-entrained concrete
Languages : en
Pages : 60
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Book Description
"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].
Author: Peter Clement Taylor
Publisher:
ISBN: 9780309673723
Category : Air-entrained concrete
Languages : en
Pages : 72
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Book Description
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.
Author: W. R. Malisch
Publisher:
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 52
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Book Description
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.
Author: Daniel Stephen Lane
Publisher:
ISBN:
Category : Air-entrained concrete
Languages : en
Pages : 22
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Book Description
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.
Author: William O. Tynes
Publisher:
ISBN:
Category : Air-entrained concrete
Languages : en
Pages : 114
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Book Description
Author: Paul Klieger
Publisher:
ISBN:
Category : Concrete
Languages : en
Pages : 28
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Book Description
Author: Abdul Hameed Khan
Publisher:
ISBN:
Category : Concrete
Languages : en
Pages : 156
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Book Description
