Mitigating Shrinkage Cracking of Concrete in Bridge Decks Through Internal Curing PDF Download

Author: Daniel Robert Goad
Publisher:
ISBN: 9781267851659
Category : Concrete
Languages : en
Pages : 160

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Book Description
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.

Author: Ardavan Ardeshirilajimi
Publisher:
ISBN:
Category : Concrete slabs
Languages : en
Pages : 91

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Book Description

Author: Pizhong Qiao (Civil engineer)
Publisher:
ISBN:
Category : Bridges
Languages : en
Pages : 0

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Book Description
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.

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: Eric Simonton
Publisher:
ISBN:
Category : Concrete
Languages : en
Pages : 302

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Book Description
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.

Author: Pizhong Qiao
Publisher:
ISBN:
Category : Bridges
Languages : en
Pages : 79

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Book Description
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.

Author: Dejian Shen
Publisher: Springer Nature
ISBN: 9811983984
Category : Technology & Engineering
Languages : en
Pages : 348

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Book Description
This monograph is written based on the author's research on the assessment, control, and repair of cracking of early-age concrete in the recent decade. The technique of internal curing for increasing cracking resistance of early-age concrete is further developed through experimental and theoretical research. It establishes models for predicting the internal relative humidity and autogenous shrinkage of internally cured concrete at early age; reveals the variation law and mechanism of early-age tensile creep of internally cured concrete; and explores the variation law and mechanism of early-age cracking resistance of internally cured concrete under continuous restrained condition or uniaxial restrained condition. It is designed as a reference work for professionals or practitioners and a textbook for undergraduates or postgraduates. As such, this book provides valuable knowledge, useful methods, and practical experience that can be considered in the field of concrete cracking control.

Author: John Schlitter
Publisher:
ISBN: 9781622600311
Category :
Languages : en
Pages :

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Author: Waleed Khalid Hamid
Publisher:
ISBN:
Category : Bridges
Languages : en
Pages :

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Book Description
The long-term performance of a bridge deck depends on its resistance to bridge cracking. Most of these cracks are initiated at the early age. Early age cracking of bridge decks is a typical issue in the U.S. that reduces bridge service life. Therefore, internally cured concrete (ICC) has been used in some states to reduce or eliminate the development of cracks in reinforced concrete decks. In this study, the early age behavior of ICC deck and the effect of the internal curing on the long-term behavior of the bridge was measured and evaluated in the laboratory and field for newly adjacent constructed bridge, which were located on Route 271 in Mayfield, Ohio. Two different types of concrete mixtures were utilized for the decks: conventional concrete (CC) and internally cured concrete (ICC). Firstly, the ICC and CC mixtures were examined in the laboratory in terms of a mechanical properties test, a plastic shrinkage test, a free shrinkage test, and a restrained shrinkage test. Second, the field behavior of an ICC deck and an adjacent CC deck during their early age and long-term performance were evaluated. Also, the shrinkage development for both decks was examined during the very early age. Instrumentation was used to measure the concrete and reinforcement strains and the temperature in both bridges. The instrumentation and results for both bridges are discussed. Laboratory results indicated that using pre-wetted lightweight concrete in the concrete mixture led to decreased density, coefficient of thermal expansion, and free shrinkage strain, and increased tensile strength and cracking time of concrete compared to conventional concrete. In the field, from the early age test, it was observed that the time to develop concrete shrinkage was approximately 5-6 hours after casting the deck of the ICC and the CC.

Author: Timothy J. Barrett
Publisher:
ISBN:
Category : Concrete
Languages : en
Pages : 483

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Book Description
The Indiana Department of Transportation (INDOT) commissioned the construction of six bridge decks utilizing a new class of internally cured high performance concrete (IC HPC). The first four bridge decks were constructed in the summer of 2013, while the fifth was built in November of 2014 and the sixth is planned for the summer of 2015. These decks implement research findings presented in the FHWA/IN/JTRP-2010/10 report (Schlitter, Henkensiefken, et al. 2010) where internal curing was proposed as one method to reduce the potential for shrinkage cracking, leading to improved durability. In addition, the use of higher performance concrete mixtures and a new specification composed of prescriptive and performance based measures was implemented with the intention of extending the service life of the bridge decks. The objectives of this thesis are to provide documentation of the construction and performance of the IC HPC bridge decks cast in Indiana and provide a viable, practice-ready method for the assessment of the potential durability of these concretes. In fulfillment of these objectives, samples of the IC HPC used in construction were compared to a reference high performance concrete (HPC) which did not utilize internal curing and was made by the same producer with the same constituent materials. The samples collected in the field were transported to the laboratory where the mechanical performance, resistance to chloride ingress, and potential for shrinkage and cracking was assessed. Using experimental results and mixture proportions, the diffusion based service life of the bridge decks was able to be estimated. The construction process was documented for first four bridge decks made using internal cured high performance concrete (IC HPC). These concretes were able to be designed, batched, and placed and are now in service. While avoidable issues were observed during batching construction related to corrections of batching water, batching tolerances and fluctuations in air content (which apply to any concrete), the IC HPC was able to be batched and placed using slight modifications to conventional methods. The production of the IC HPC mixtures was implemented using a mixed specification using prescriptive and performance based measures representing an improvement on previous specifications which did not specifically have provisions that consider durability. To aid in the implementation of internal curing in the field, a new quality control technique for lightweight aggregate utilizing a centrifuge has been implemented is now standardized in Indiana Testing Method 222 (Miller, Barrett, et al. 2014). The results of laboratory testing indicate that the compressive strength, modulus of elasticity, and tensile strength of the IC HPC mixtures was not substantially different than the HPC mixtures and as such current codified equations are able to be used to predict the modulus of elasticity and tensile strength if the compressive strength is known. The diffusion of chlorides in these concretes was assessed, where it was shown that each of the mixtures tested had a charge passed in the rapid chloride permeability test of less than 1500 C at 91 days (AASHTO T277-07 2007); additional testing provided equivalent results when performing the Nordtest (NT Build 492 1999), Stadium migration test , or electrical resistivity test. Using experimental results which determined the chloride diffusion and permeability, the diffusion based service life of the IC HPC bridge decks was estimated to be between approximately 60 to 90 years, compared to approximately 18 years for the conventional class C bridge deck concrete used in Indiana. The susceptibility to early age shrinkage and cracking was evaluated where it was shown that IC HPC concretes exhibited a reduction in early age shrinkage of 70 to 90%, resulting in a reduction in residual stresses of 80% or more while reducing thermally induced stress by up to 55% when compared to HPC mixtures. Collectively, these results indicate that the IC HPC mixtures that were produced as a part of this study exhibit the potential of for substantially increased service life while markedly reducing the potential for early age cracking. The second phase of this thesis investigated the role of initial sample conditioning and the effect of changes in degree of saturation on the measured electrical resistivity, where a new function was developed to describe this relationship in air entrained concretes. The consistency and variability in the determination of the chloride diffusion coefficient was investigated through standardized testing methods, where it was shown that the coefficient of variation associated with the accelerated tests was approximately 15% or less and are dependent on the test. Chloride profile measurements made on cores taken from samples which were exposed with a known deicing solution and the temperature fluctuations of West Lafayette, Indiana indicated that on average, the coefficient of variation for determining the apparent chloride diffusion coefficient under is 30% or less. In addition, the use of resistivity measurements on sealed samples was used to evaluate the variability of the concrete produced throughout the construction of the fifth IC HPC bridge deck while comparisons of the samples from the first four bridge decks produced in the laboratory and in the field were also made. The results indicated that the coefficient of variation associated with the resistivity measurements made on the fifth bridge deck was less than 5%, while experimental results indicated that industrial production consistently results in lower performance as measured by the resistivity test when compared to laboratory production. In this study it was also shown that measurements of mechanical properties are not indicative of the potential durability of the concrete. The conclusions of this thesis and the findings presented in the FHWA/IN/JTRP-2010/10 report (Schlitter, Henkensiefken, et al. 2010) and the CDOT-2014-3 report (Jones et al. 2014) indicate that internal curing is a practice-ready, engineered solution that may lead to the production of higher performance concretes which have a reduced potential for cracking. To aid in the implementation of internal curing in practice, spreadsheets which automate calculations necessary for quality control for lightweight aggregates, mixture proportioning, and moisture adjustments have been developed by Miller (2014) and have been made available with the report documenting the construction of the first four bridge decks (Barrett et al. 2015). This thesis also provided the framework for a durability based design approach using sealed electrical resistivity measurements which may be implemented in practice. This method has been shown to be a viable way to rapidly evaluate the chloride diffusion coefficient of concrete and is appropriate for testing large numbers of samples during construction. It is recommended that the approach outlined in this work be implemented in performance based specifications in lieu of other accelerated testing methods which define the performance of the concrete based on the result of that test. Finally, it should be emphasized that the implementation of technologies such as those that are presented in this thesis alone does not guarantee higher performance, as the production of such concrete requires a degree of technical competence in design, production, and construction of concrete materials. As is the case with the production of any concrete, internally cured or not, performance will be directly tied to the careful accounting of water, be it on the surface of aggregates, in the mixing drum after washing, or elsewhere. Special attention should be paid to the proper operation of batching systems, while placement techniques should be reviewed to minimize unwanted effects, and proper finishing and curing techniques must always be practiced. Only after performing the basics of concrete production properly will the full benefits of internal curing be actualized.