Enhanced Entrained Air Void System Characterization for Durable Highway Concrete PDF Download
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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: 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: David Whiting
Publisher: Transportation Research Board National Research
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 96
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Book Description
Author: Chao Xiao
Publisher:
ISBN:
Category :
Languages : en
Pages : 54
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Book Description
Author: ZAFAR AHMED MALIK
Publisher:
ISBN:
Category :
Languages : en
Pages : 530
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Book Description
Two-way analysis of variance showed that type of air entraining agent, quality of aggregate, and content of condensed silica fume have a major effect on freeze-thaw durability of concrete.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author:
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ISBN:
Category :
Languages : en
Pages :
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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: José Sena-Cruz
Publisher: Springer Nature
ISBN: 3030764656
Category : Technology & Engineering
Languages : en
Pages : 361
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Book Description
This book gathers peer-reviewed contributions presented at the 3rd RILEM Spring Convention and Conference, held at Guimarães and hosted by the University of Minho, Portugal, on March 9-14, 2020. The theme of the Conference was “Ambitioning a Sustainable Future for Built Environment: comprehensive strategies for unprecedented challenges”, which was aimed at discussing current challenges and impacts of the built environment on sustainability. The present volume is dedicated to the topic “Service life extension of existing structures”, which covers the most recent scientific and technological developments in the understanding of the evolution and degradation of construction materials and structural systems. Analytical and numerical, as well as experimental approaches, aimed at characterizing, modelling and predicting the evolution of the physical, chemical and mechanical properties of construction materials and structural systems are regarded. Multiphysics models are also considered, as well as other strategies that contribute for an accurate characterization and prediction the service life and the evolution of existing and novel construction materials under normal or extreme environmental exposure or loading conditions. New strategies to promote the smart repairing or the recovery of material properties, as well as the service life extension, are also considered. The following subtopics are included: service life models and multiphysics approaches; smart structures, innovative monitoring and intervention strategies; management and optimized maintenance strategies; integrated rehabilitation and strengthening approaches.
