Curing Practices to Reduce Plastic Shrinkage in Concrete Bridge Decks

Curing Practices to Reduce Plastic Shrinkage in Concrete Bridge Decks
Author: Steven W. Peyton
Publisher:
Total Pages:
Release: 2011
Genre: Bridges
ISBN:

"The large, exposed area of concrete bridge decks makes proper curing critical and difficult. Plastic shrinkage cracks are common in improperly cured bridge decks. The objective of this research was to identify curing regimens that successfully reduce plastic shrinkage cracking. This was accomplished by surveying Arkansas Highway and Transportation Department engineers to determine the current construction practices on Arkansas bridge decks, documenting the curing of five bridge decks under construction, and studying the effectiveness of curing regimens in the laboratory. The survey responses show inconsistencies in the interpretations of the construction specifications that were also evident in the field study. Delayed curing, high evaporation rate, and increased girder deflection increased the likelihood of cracking in the decks. Inconsistent application of curing materials caused increased cracking in the laboratory study. Removing impediments, such as tined finishes, to timely curing and clarifying curing specifications would reduce cracking in bridge decks."--Project summary.

Mitigating Shrinkage Cracking of Concrete in Bridge Decks Through Internal Curing

Mitigating Shrinkage Cracking of Concrete in Bridge Decks Through Internal Curing
Author: Daniel Robert Goad
Publisher:
Total Pages: 160
Release: 2013
Genre: Concrete
ISBN: 9781267851659

As the need for durable, long lasting infrastructure increases, new methods and techniques are being explored to prolong the service life of roads and bridges. One method to reduce shrinkage and early age cracking in concrete is internal curing. Internal curing supplies water to concrete, using pre-wetted lightweight aggregate (LWA), as needed throughout the process of hydration to reduce self desiccation, which leads to cracking. This research project analyzed two types of coarse LWA, expanded clay and expanded shale. The mixtures were developed specifically for use in bridge decks and adhered to specifications of the Arkansas State Highway and Transportation Department (AHTD). The concrete mixtures contained LWA at rates of 0, 100, 200, and 300 lb/yd3. The research was divided into two phases. The first phase measured autogenous and drying shrinkage in both plastic and elastic states using embedded vibrating wire strain gages (VWSG) cast in concrete prisms. The expanded clay LWA mixtures, with the 300 lb. replacement rate yielding the best results, were most effective in reducing shrinkage. Compressive strength decreased as the amount of LWA included in the mixture increased. However, all mixtures surpassed the 28 day compressive strength specified by AHTD. The second phase of the research project measured plastic shrinkage cracking in thin concrete test slabs. Methods and materials were investigated to produce consistent plastic shrinkage surface cracks of the concrete slabs. The extent of plastic shrinkage that occurred was quantified by measuring the total crack area of the test slabs. Implementation of 300 lb. of expanded clay LWA did not reduce the crack lengths, but did reduce the average crack widths experienced by the test slabs due to plastic shrinkage.

Low Shrinkage Mix Designs to Reduce Early Cracking of Concrete Bridge Decks

Low Shrinkage Mix Designs to Reduce Early Cracking of Concrete Bridge Decks
Author: Eric Simonton
Publisher:
Total Pages: 302
Release: 2020
Genre: Concrete
ISBN:

Abstract Shrinkage cracking is reducing the service life of concrete bridge decks in South Dakota due to premature deterioration. In this study, the effects of varying concrete mix design parameters on autogenous and drying shrinkage was observed. Tested mix design changes include aggregate type (limestone and quartzite) and gradations (ASTM C33, Tarantula Curve, and 0.45 Power Curve), supplementary cementitious materials (fly ash), cementitious content, water-to-cementitious ratio, internal curing using saturated lightweight aggregates (expanded shale), and shrinkage reducing admixtures. These changes were evaluated for their effect on the shrinkage of paste, mortar, and concrete as measured by ASTM C1698 (autogenous shrinkage) and ASTM C157 (drying shrinkage). Fresh property tests, compressive strength, and electrical resistivity measurements were performed on each mix as well. A survey of state Department of Transportations revealed the current state-of-the-art practices on shrinkage reduction in bridge decks, including the use of admixtures, internal curing agents, and external curing methods.

Reducing Cracks in Concrete Bridge Decks Using Shrinkage Reducing Admixture

Reducing Cracks in Concrete Bridge Decks Using Shrinkage Reducing Admixture
Author: Harikrishnan Nair
Publisher:
Total Pages: 0
Release: 2016
Genre: Concrete
ISBN:

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

Reducing Cracks in Concrete Bridge Decks Using Shrinkage Reducing
Author: Harikrishnan Nair
Publisher:
Total Pages: 44
Release: 2016
Genre: Concrete
ISBN:

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.

Study on Reduction of Shrinkage Cracks in Bridge Deck Concrete

Study on Reduction of Shrinkage Cracks in Bridge Deck Concrete
Author: Rajesh Anumakonda
Publisher:
Total Pages:
Release: 2006
Genre:
ISBN:

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.