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Phase I: Minimization of Cracking in New Concrete Bridge Decks

2016 Concrete bridges
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Release : 2016
Genre : Concrete bridges
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Book Synopsis Phase I: Minimization of Cracking in New Concrete Bridge Decks by : Nicole Duffala

Download or read book Phase I: Minimization of Cracking in New Concrete Bridge Decks written by Nicole Duffala. This book was released on 2016. Available in PDF, EPUB and Kindle. Book excerpt: Cracking of newly constructed high-performance concrete (HPC) bridges is a problem recognized nationwide and the Nevada Department of Transportation has been plagued with this distress in their HPC concrete bridge decks. This research effort is a strategic attempt to reduce or eliminate random cracking that is caused by restrained shrinkage in new concrete bridge decks constructed in Nevada. The overall objective will be achieved through a three phase research program of which the results of Phase I are being reported in this document. Phase I research findings provide a synthesis of state, regional, and national practices and knowledge on factors contributing to HPC bridge deck cracking. With respect to materials and mixture proportioning, the overwhelming conclusion is that the shrinkage of the concrete mixture, especially at early-ages, must be reduced and the concrete’s resistance to cracking must be Improved. A rigorous, Phase II laboratory experiment was designed and is presented herein. This Phase II laboratory experiment focuses on local materials and will assess the properties of concrete mixtures that are related to early-age drying shrinkage restraint cracking. Ultimately, these research findings could be used to revise standard specifications and special provisions for Nevada DOT bridge decks and eventually reduce the overall incidence of restraint cracking due to concrete drying shrinkage.

Reducing Cracks in Concrete Bridge Decks Using Shrinkage Reducing Admixture

2016 Concrete
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Release : 2016
Genre : Concrete
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Book Synopsis Reducing Cracks in Concrete Bridge Decks Using Shrinkage Reducing Admixture by : Harikrishnan Nair

Download or read book Reducing Cracks in Concrete Bridge Decks Using Shrinkage Reducing Admixture written by Harikrishnan Nair. This book was released on 2016. Available in PDF, EPUB and Kindle. Book excerpt: Restrained shrinkage cracking of concrete bridge decks creates a significant durability problem. Major admixture suppliers in the United States have introduced a new category of chemical admixtures called shrinkage reducing admixtures (SRAs). SRAs work by reducing the surface tension of pore water and thereby decreasing the capillary stress and shrinkage induced by drying. Several studies have reported that using SRAs in concrete mixtures is one of the most effective ways of reducing shrinkage cracking. The purpose of this study was to investigate the effectiveness of SRAs in reducing drying shrinkage in Virginia Department of Transportation (VDOT) concrete mixtures and thus reducing cracks in bridge decks. Nine bridges located in VDOT's Northern Virginia, Staunton, and Fredericksburg districts were selected for study. Three different SRA products were used. With the exception of one mixture, the maximum cementitious content was limited to 600 lb/yd3. Fresh and hardened concrete properties were determined for each mixture, and field placement details were documented. The results showed that low cementitious concrete with SRA was effective in minimizing bridge deck cracking. The study showed that bridges with fewer and narrower cracks or no cracks can be constructed and that proper construction practices are needed to reduce bridge deck cracking. The study recommends the use of SRA with a lower cementitious content in VDOT bridge deck concrete mixtures. A VDOT special provision was developed for the future use of SRA in concrete mixtures.

Reducing Cracks in Concrete Bridge Decks Using Shrinkage Reducing

2016 Concrete
Download Reducing Cracks in Concrete Bridge Decks Using Shrinkage Reducing PDF Online Free

Author :
Release : 2016
Genre : Concrete
Kind : eBook
Book Rating : /5 ( reviews)

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Book Synopsis Reducing Cracks in Concrete Bridge Decks Using Shrinkage Reducing by : Harikrishnan Nair

Download or read book Reducing Cracks in Concrete Bridge Decks Using Shrinkage Reducing written by Harikrishnan Nair. This book was released on 2016. Available in PDF, EPUB and Kindle. Book excerpt: Restrained shrinkage cracking of concrete bridge decks creates a significant durability problem. Major admixture suppliers in the United States have introduced a new category of chemical admixtures called shrinkage reducing admixtures (SRAs). SRAs work by reducing the surface tension of pore water and thereby decreasing the capillary stress and shrinkage induced by drying. Several studies have reported that using SRAs in concrete mixtures is one of the most effective ways of reducing shrinkage cracking. The purpose of this study was to investigate the effectiveness of SRAs in reducing drying shrinkage in Virginia Department of Transportation (VDOT) concrete mixtures and thus reducing cracks in bridge decks. Nine bridges located in VDOT Northern Virginia, Staunton, and Fredericksburg districts were selected for study. Three different SRA products were used. With the exception of one mixture, the maximum cementitious content was limited to 600 lb/yd3. Fresh and hardened concrete properties were determined for each mixture, and field placement details were documented. The results showed that low cementitious concrete with SRA was effective in minimizing bridge deck cracking. The study showed that bridges with fewer and narrower cracks or no cracks can be constructed and that proper construction practices are needed to reduce bridge deck cracking. The study recommends the use of SRA with a lower cementitious content in VDOT bridge deck concrete mixtures. A VDOT special provision was developed for the future use of SRA in concrete mixtures.

Mitigation Strategies for Early-age Shrinkage Cracking in Bridge Decks

2010 Bridges
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Author :
Release : 2010
Genre : Bridges
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Book Synopsis Mitigation Strategies for Early-age Shrinkage Cracking in Bridge Decks by : Pizhong Qiao (Civil engineer)

Download or read book Mitigation Strategies for Early-age Shrinkage Cracking in Bridge Decks written by Pizhong Qiao (Civil engineer). This book was released on 2010. Available in PDF, EPUB and Kindle. Book excerpt: Early-age shrinkage cracking has been observed in many concrete bridge decks in Washington State and elsewhere around the U.S. The cracking increases the effects of freeze-thaw damage, spalling, and corrosion of steel reinforcement, thus resulting in premature deterioration and structural deficiency of the bridges. In this study, the main causes of the early-age cracking in the decks are identified, and concrete mix designs as a strategy to prevent or minimize the shrinkage cracking are evaluated. Different sources (eastern and western Washington) and sizes of aggregates are considered, and the effects of paste content, cementitious materials (cement, fly ash, silica fume, slag), and shrinkage reducing admixture (SRA) are evaluated. A series of fresh, mechanical and shrinkage property tests were performed for each concrete mix. The outcomes of this study identify optimum concrete mix designs as appropriate mitigation strategies to reduce or eliminate early-age shrinkage cracking and thus help minimize shrinkage cracking in the concrete bridge decks, potentially leading to longer service life.

Study on Reduction of Shrinkage Cracks in Bridge Deck Concrete

2006
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Release : 2006
Genre :
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Book Synopsis Study on Reduction of Shrinkage Cracks in Bridge Deck Concrete by : Rajesh Anumakonda

Download or read book Study on Reduction of Shrinkage Cracks in Bridge Deck Concrete written by Rajesh Anumakonda. This book was released on 2006. Available in PDF, EPUB and Kindle. Book excerpt: Shrinkage is an unavoidable property of concrete that can lead to cracking, thereby limiting the serviceability of concrete structures. Shrinkage cannot be eliminated but can be minimized. Shrinkage cracking can be a critical problem in concrete construction, especially for flat slab structures such as highway pavements, industrial slab-on-grade, for parking garages, and bridge decks. The primary objective of the research is to evaluate three practical methods to reduce shrinkage cracks in concrete for bridge deck applications. The three methods evaluated are: 1) use of optimized aggregate gradation concrete, 2) use of a new high performance concrete known as low-cracking high performance concrete (LC-HPC) and 3) the use of Fibra Shield Fibers to reduce plastic shrinkage cracking in concrete.

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