Effect of Larger Sized Coarse Aggregates on Mechanical Properties of Portland Cement Concrete Pavements and Structures PDF Download
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Author:
Publisher:
ISBN:
Category : Pavements, Concrete
Languages : en
Pages : 172
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Book Description
ODOT is continually searching for ways to improve the cost efficiency of Portland cement concrete without sacrificing concrete strength and stiffness. Because Portland cement is easily the most costly material used in normal concrete, limiting the amount of cement used is the quickest way to achieve cost effectiveness. In addition, limiting the cement content will also help to prevent dimensional instabilities in concrete such as shrinkage and creep. The use of larger sized coarse aggregates may be useful in limiting cement content, yet larger sized coarse aggregates may also decrease concrete strength by weakening the aggregate-cement paste bond. In many transportation structures, such as pavements, concrete strength is not critical, as dimensional stability, porosity, and durability play a more important role. It is possible, therefore, that larger sized coarse aggregates can reduce the cement content and improve these properties. Laboratory research is needed to determine if larger sized coarse aggregates can improve cement efficiency without reducing concrete strength.
Author:
Publisher:
ISBN:
Category : Pavements, Concrete
Languages : en
Pages : 172
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Book Description
ODOT is continually searching for ways to improve the cost efficiency of Portland cement concrete without sacrificing concrete strength and stiffness. Because Portland cement is easily the most costly material used in normal concrete, limiting the amount of cement used is the quickest way to achieve cost effectiveness. In addition, limiting the cement content will also help to prevent dimensional instabilities in concrete such as shrinkage and creep. The use of larger sized coarse aggregates may be useful in limiting cement content, yet larger sized coarse aggregates may also decrease concrete strength by weakening the aggregate-cement paste bond. In many transportation structures, such as pavements, concrete strength is not critical, as dimensional stability, porosity, and durability play a more important role. It is possible, therefore, that larger sized coarse aggregates can reduce the cement content and improve these properties. Laboratory research is needed to determine if larger sized coarse aggregates can improve cement efficiency without reducing concrete strength.
Author: Kristina M. Cannady
Publisher:
ISBN:
Category :
Languages : en
Pages : 75
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Book Description
This project examines whether the addition of microsilica or the use of aggregates with maximum size above 1.5 in., in concrete mixes prepared by the Ohio Department of Transportation (ODOT) for bridge decks and highway pavements, can have adverse effects on the durability properties of such structures. The behavior of several series of concrete specimens has been monitored over a period exceeding a year, and measurements of shrinkage, creep, abrasion, rapid chloride permeability, and freeze/thaw resistance have been recorded. Such data are evaluated to determine if altering the standard ODOT concrete mix design on either end of the gradation spectrum can indeed lower the cement content and increase its cost effectiveness and efficiency. It was found that different coarse aggregate gradations did not impact significantly the environmental properties of concrete examined. Variability issues related to the testing protocols themselves confounded the differences observed. These results indicate that larger sized coarse aggregates can be used for pavements and highway structures without significantly compromising the environmental properties of the concrete, and afford concrete producers more flexibility in creating cost-effective and cement-efficient mixes. It was found earlier in State Job No. 14800(0) that the compressive and flexural strengths of abused microsilica did not differ much from that of densified microsilica. This conclusion is brought into question, at least in the case of abused microsilica, by the rapid chloride permeability results obtained. Nonetheless, all values obtained are within the limits termed as low or moderate by the prevailing specifications.
Author: Nader Ghafoori
Publisher: CRC Press
ISBN: 0203859928
Category : Technology & Engineering
Languages : en
Pages : 1032
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Book Description
Challenges, Opportunities and Solutions in Structural Engineering and Construction addresses the latest developments in innovative and integrative technologies and solutions in structural engineering and construction, including: Concrete, masonry, steel and composite structures; Dynamic impact and earthquake engineering; Bridges and
Author: James Stanley Fergus
Publisher:
ISBN:
Category : Pavements, Concrete
Languages : en
Pages : 374
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Author:
Publisher:
ISBN:
Category : Aggregates (Building materials)
Languages : en
Pages : 220
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Author: B. Frank McCullough
Publisher:
ISBN:
Category : Aggregates (Building materials)
Languages : en
Pages : 118
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This report focuses on aggregates used in the construction of continuously reinforced concrete pavements (CRCP). Specific chapters address (1) past research regarding aggregates used in CRCP, (2) field and laboratory investigations of CRCP, and (3) CRCP behavior and distress. The report reviews such topics as spalling and punchout distresses in continuously reinforced and jointed pavements, aggregate shape characterization using fractals, and the determination of sawcut depth using fractal analysis. Some of these activities relate directly to improving pavement performance, regardless of aggregate type used for construction.
Author: American Concrete Paving Association. Materials and Mix Design Technical Subcommittee
Publisher:
ISBN:
Category : Aggregates (Building materials)
Languages : en
Pages : 28
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Author: Joseph F. Lamond
Publisher: ASTM International
ISBN: 0803133677
Category : Technology & Engineering
Languages : en
Pages : 661
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Author: Norbert J. Delatte
Publisher:
ISBN:
Category : Bridges
Languages : en
Pages : 148
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Book Description
Early age cracking of bridge decks is a national problem, and may substantially reduce service lives and increase maintenance costs. Cracking occurs when the tensile stress exceeds the tensile strength of the concrete. This is a time-dependent phenomenon, since both the stress and strength change at early ages. Moisture loss increases stress (with increasing shrinkage) and impairs strength gain. Internal curing is one method that has been suggested to reduce early age bridge deck cracking, particularly of concretes with low water to cementitious materials (w/cm) ratios. Many state highway agencies have implemented high performance concrete (HPC) for bridge decks. The low permeability of HPC is used to protect reinforcing steel and prevent corrosion. However, if the concrete cracks, then the protection may be greatly diminished. Transverse cracks due to concrete shrinkage allow water and corrosive chemicals to quickly reach the reinforcing steel causing corrosion and shortening the lifespan of the bridge deck. Reducing shrinkage cracking has been the focus of recent research into mitigation strategies. One unintended consequence of the use of high performance concrete may be early-age cracking. Field studies have shown that, in some cases, high performance concrete bridge decks have cracked less than a year after placement. The use of internal curing to reduce autogenous shrinkage was investigated in this study. One method of internal curing was through the use of coarse aggregates with high absorption capacities. Another method discussed is the use of a partial replacement of the fine aggregate with a structural lightweight aggregate with a very high absorption capacity. Bridge deck cracking is also affected by the nominal maximum size coarse aggregate. The effect on shrinkage with increasing size is discussed. ODOT's District 12, located in Northeastern Ohio, found in an investigation of 116 HPC bridge decks placed between 1994 and 2001 that bridges with little or no cracking used coarse aggregate with an absorption> 1 %, while 75 % of bridges with unacceptable cracking used coarse aggregate with absorption 1 %. This report discusses the laboratory investigation of the field results to determine the better ways to prevent bridge deck cracking-- internal curing or paste reduction by using an aggregate blend. The laboratory investigation found that the strongest effect on cracking was due to the replacement of a small maximum size coarse aggregate with an optimized coarse aggregate gradation. Increasing the coarse aggregate absorption level from
Author: Steven M. Cramer
Publisher:
ISBN:
Category : Aggregates (Building materials)
Languages : en
Pages : 56
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