An Investigation Into the Effects of Fly Ash on Freeze-thaw Durability Prediction PDF Download
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Author: Yancy Schrader
Publisher:
ISBN:
Category :
Languages : en
Pages : 64
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Book Description
Air is purposefully entrained into concrete primarily to improve resistance to freeze-thaw deterioration while saturated with water. Air entraining admixtures (AEAs) are chemical admixtures designed to entrain air into the concrete to provide adequate resistance to the effects of freezing and thawing. One of the challenges associated with air entrainment in concrete is the interaction of an AEA with supplementary cementitious materials present in the concrete, particularly fly ash. Fly ash is a by-product of the coal fired electrical generation industry, and often contains residual unburned carbon and other components that can increase the AEA demand of a particular concrete mix. Properly estimating the amount of AEA required to reach the specified air content in a concrete containing fly ash is of utmost importance to the ready mix concrete supplier, as an insufficient air content may lead to job site rejection and the resultant monetary losses. This study aimed to better relate fly ash and concrete properties obtainable prior to final concrete placement, to direct measures of concrete durability obtainable only after the concrete has set and been put into service. A new device known as the Super Air Meter (SAM) was studied concurrently to better examine the relationship between its System Air Metric number (SAM number) and hardened concrete durability properties. Generally, fly ashes with higher foam index values and surface areas required higher dosages of AEAs to reach a specified air content value. No such relationship could be determined with the more commonly available loss on ignition percentage of the fly ash. The SAM number correctly predicted an acceptable spacing factor in 9 out of 12 different concretes tested, although all of the concretes tested displayed poor performance in freeze-thaw durability. These results demonstrate that air content testing alone is not necessarily sufficient to ensure high quality, durable concrete structures.
Author: Yancy Schrader
Publisher:
ISBN:
Category :
Languages : en
Pages : 64
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Book Description
Air is purposefully entrained into concrete primarily to improve resistance to freeze-thaw deterioration while saturated with water. Air entraining admixtures (AEAs) are chemical admixtures designed to entrain air into the concrete to provide adequate resistance to the effects of freezing and thawing. One of the challenges associated with air entrainment in concrete is the interaction of an AEA with supplementary cementitious materials present in the concrete, particularly fly ash. Fly ash is a by-product of the coal fired electrical generation industry, and often contains residual unburned carbon and other components that can increase the AEA demand of a particular concrete mix. Properly estimating the amount of AEA required to reach the specified air content in a concrete containing fly ash is of utmost importance to the ready mix concrete supplier, as an insufficient air content may lead to job site rejection and the resultant monetary losses. This study aimed to better relate fly ash and concrete properties obtainable prior to final concrete placement, to direct measures of concrete durability obtainable only after the concrete has set and been put into service. A new device known as the Super Air Meter (SAM) was studied concurrently to better examine the relationship between its System Air Metric number (SAM number) and hardened concrete durability properties. Generally, fly ashes with higher foam index values and surface areas required higher dosages of AEAs to reach a specified air content value. No such relationship could be determined with the more commonly available loss on ignition percentage of the fly ash. The SAM number correctly predicted an acceptable spacing factor in 9 out of 12 different concretes tested, although all of the concretes tested displayed poor performance in freeze-thaw durability. These results demonstrate that air content testing alone is not necessarily sufficient to ensure high quality, durable concrete structures.
Author: BW. Langan
Publisher:
ISBN:
Category : Concrete
Languages : en
Pages : 4
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Book Description
This investigation studied the effect of interrupted testing combined with prolonged freezing on the freeze-thaw resistance of concretes containing fly ash as part of the cementitious fraction, using ASTM Test Method for Resistance of Concrete to Rapid Freezing and Thawing (C 666-84, Method A). Also studied was the effect of "marginal" air contents on the above test parameters. Test results indicate that for fly ash concretes with air contents in excess of 5%, interrupted and/or prolonged periods of freezing do not affect the freeze-thaw resistance of the concrete. Early age freezing (14 days) of fly ash concretes did not appear to be detrimental to the performance of the fly ash concretes tested.
Author: Kurt F. von Fay
Publisher:
ISBN:
Category : Concrete
Languages : en
Pages : 68
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Author: Ian Anderson
Publisher:
ISBN:
Category :
Languages : en
Pages : 112
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Therefore, the specific objectives of this study were to: (1) determine the effects of deicing salts on pervious concrete, using a modified and more field representative testing procedure that involves slow freeze-thaw cycling in drained condition, and (2) determine the effects of cement replacement with increasing amounts of fly ash on the freeze-thaw, durability of pervious concrete.
Author: Ken Isenberger
Publisher:
ISBN:
Category : Fly ash
Languages : en
Pages : 42
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Book Description
Effect of fly ash class, source and amount on the compressive strength and freeze-thaw durability of fly ash concrete.
Author: M. G. Rosa
Publisher:
ISBN:
Category : Fly ash
Languages : en
Pages : 16
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Book Description
The objective of this research was to develop a freeze-thaw cycling test procedure and to investigate how the volume, moisture content, resilient modulus (Mr), and unconfined compressive strength (qu) of geomaterials, including soils and recycled materials, stabilized with fly ash change after freeze-thaw cycling. Three different types of materials (fine-grained and coarse-grained soils and recycled pavement materials) and five different fly ashes were used at different percentages (10, 12, 14, and 20 % by dry weight). Both one-dimensional and three-dimensional freezing of the specimens were considered. Freezing in three-dimensional was faster in terms of completing the freeze-thaw cycling and provided very similar results to the ones prepared in one-dimensional. Thus, three-dimensional freezing was adopted in this study without access to water (i.e., closed system). The results of this study indicated that the volume of all soil-fly ash mixtures tended to increase after freeze-thaw cycling; however, the volume change was not significant. Resilient modulus tests were conducted on all unstabilized materials, as well as on their mixtures with fly ash, while qu tests were conducted only on fine-grained soil and their fly ash mixtures. The Mr of all mixtures with one exception decreased by an average of 28.5 % when specimens were subjected to freeze-thaw cycling. The drop in the Mr of the specimens leveled off after 5 freeze-thaw cycles. A general trend of higher Mr of materials stabilized with fly ash (from 3 to 168 %), even after freeze-thaw cycles compared to unstabilized material was observed. In general, a reduction in unconfined compressive strength (qu) after freeze-thaw cycles up to 70 % was obtained. However, results showed that qu of stabilized soils that were subjected to freeze-thaw cycles were still higher (from 6 to 157 %) than the qu of unstabilized soils.
Author:
Publisher:
ISBN:
Category : Fly ash
Languages : en
Pages : 52
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Author: Maria G. Rosa
Publisher:
ISBN:
Category :
Languages : en
Pages : 384
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Author: J. Marchand
Publisher: CRC Press
ISBN: 1482271559
Category : Architecture
Languages : en
Pages : 285
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Book Description
Concrete durability in climates where freezing and thawing occurs is a continuing problem. It is particularly acute for highway and bridge structures, where de-icing salts are used to combat the effects of frost, snow and ice. These salts can cause damage to concrete and accelerate corrosion of reinforcements. This book presents the latest internat
Author: Thomas Duane Larson
Publisher:
ISBN:
Category : Concrete
Languages : en
Pages : 416
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