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Author: Arman Abdigaliyev Publisher: ISBN: Category : Bridges Languages : en Pages : 117
Book Description
Due to the relatively high cement content and low water-to-cement ratio (w/c) used, bridge deck concrete is prone to premature cracking. Internal curing has been found to greatly reduce the chance of premature cracking as well as concrete deterioration. This research developed internally cured bridge deck concrete based on a local mix design in Nebraska. Four different lightweight fine aggregate (LWFA) as internal curing agents were evaluated and their effects on fresh, mechanical, durability, and shrinkage properties of concrete were studied. The study focused on resolving two issues associated with fine aggregate replacement based on Bentz equation. To identify the most effective LWFA dosage for shrinkage reduction, different replacement rates of fine aggregates (50%, 100%, 125%, 150% and 175%) were adopted to account for the moisture loss during construction and drying period. Aggregate blends of internally cured mixes were also optimized to account for the disturbed aggregate gradations due to the introduced LWFA. Overall performance of internally cured concrete mixes with both non-optimized and optimized gradations were evaluated. The research demonstrated that effective internal curing concrete can be achieved with the optimized aggregate gradation.
Author: Arman Abdigaliyev Publisher: ISBN: Category : Bridges Languages : en Pages : 117
Book Description
Due to the relatively high cement content and low water-to-cement ratio (w/c) used, bridge deck concrete is prone to premature cracking. Internal curing has been found to greatly reduce the chance of premature cracking as well as concrete deterioration. This research developed internally cured bridge deck concrete based on a local mix design in Nebraska. Four different lightweight fine aggregate (LWFA) as internal curing agents were evaluated and their effects on fresh, mechanical, durability, and shrinkage properties of concrete were studied. The study focused on resolving two issues associated with fine aggregate replacement based on Bentz equation. To identify the most effective LWFA dosage for shrinkage reduction, different replacement rates of fine aggregates (50%, 100%, 125%, 150% and 175%) were adopted to account for the moisture loss during construction and drying period. Aggregate blends of internally cured mixes were also optimized to account for the disturbed aggregate gradations due to the introduced LWFA. Overall performance of internally cured concrete mixes with both non-optimized and optimized gradations were evaluated. The research demonstrated that effective internal curing concrete can be achieved with the optimized aggregate gradation.
Author: Jagan Mohan Rao V. V. Kanaparthi Publisher: ISBN: Category : Languages : en Pages :
Book Description
This thesis summarizes the results of an experimental investigation on the performance evaluation of bridge deck concrete made with optimized aggregate gradation. The research conducted was part of the project sponsored by South Dakota Department of Transportation. The primary objective of the projects is to validate the research findings of the laboratory concrete against the performance of field concrete that used optimized aggregate gradation. The performance of field concrete used in three newly constructed bridge decks was evaluated by conducting a series of laboratory tests to determine compressive strength, modulus of elasticity, drying shrinkage resistance, alkali aggregate reactivity, sulfate attack, freeze-thaw durability, and rapid chloride permeability. This also includes measuring and documenting of the extent of cracks developed in the new bridge decks, and comparing with that of other similar existing bridges in the state. The study revealed that field concrete had good workability and finishability. The fresh concrete and micro-structural properties of the field concrete are similar to that of control concrete and the optimum laboratory concrete. The average compressive strength of the field concrete was higher that of control concrete and optimum laboratory concrete. The field concrete showed better resistance to sulfate attack, chloride permeability, drying shrinkage, alkali aggregate reactivity, and freeze-thaw exposure than control concrete and optimum laboratory concrete. The total number of cracks and the corresponding crack areas in the new bridge decks were significantly smaller than those of bridge decks made from A-45 concrete. It is recommended that the optimized aggregate gradation mixture proportions of Class F fly ash (20% cement replacement by weight) be specified for bridge deck concrete. Crack surveys need to be carried out on the new bridges annually for next three years to monitor any potential deterioration.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
As of 2005, 23% of the bridges in the Kansas infrastructure are classified as structurally deficient or functionally obsolete according to the ASCE Infrastructure Report Card (ASCE, 2008). One alternative to replacing the entire bridge structure is replacing only the superstructure with lightweight concrete. This option is more economical for city, county, and state governments alike. Replacing the superstructure with lightweight concrete can oftentimes allow the bridge rating to be upgraded to higher load capacities or higher traffic volumes. Furthermore, lightweight concrete can be used initially in a bridge deck to provide reduced weight and a lower modulus of elasticity, therefore lower cracking potential. The Kansas Department of Transportation is interested in the potential benefits of using lightweight aggregate concrete in Kansas bridge decks and prestressed bridge girders. This research project used three types of lightweight aggregate to develop lightweight concrete mixtures for a bridge deck and for prestressed bridge girders. Two of the lightweight aggregates were expanded shale obtained locally from the Buildex Company. One deposit was located in Marquette, Kansas, and the other in New Market, Missouri. The third lightweight aggregate source was expanded slate obtained from the Stalite Company in North Carolina. Aggregate properties including absorption, gradation, and L.A. Abrasion were evaluated. Over 150 lightweight concrete mixtures were created and tested and several mix design variables such as water-to-cement ratio, cement content, and coarse-to-fine aggregate ratio were evaluated. From these results, optimized bridge deck and optimized prestressed concrete mixtures were developed for each type of lightweight aggregate. Special concerns for lightweight aggregate concrete are addressed. These optimized concrete mixtures were then tested for KDOT acceptability standards for the concrete properties of compressive strength, tensile strength, modulus of elasticity, freeze-thaw resistance, permeability, alkali-silica reactivity, drying shrinkage, and autogenous shrinkage. All concrete mixtures performed satisfactorily according to KDOT standards. In addition, an internal curing effect due to the moisture content of the lightweight aggregate was observed during the autogenous shrinkage test.
Author: Norbert J. Delatte Publisher: ISBN: Category : Bridges Languages : en Pages : 148
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: Sarah Jo Grotheer Publisher: ISBN: Category : Concrete bridges Languages : en Pages : 198
Book Description
As of 2005, 23% of the bridges in the Kansas infrastructure are classified as structurally deficient or functionally obsolete according to the ASCE Infrastructure Report Card (ASCE, 2008). One alternative to replacing the entire bridge structure is replacing only the superstructure with lightweight concrete. This option is more economical for city, county, and state governments alike. Replacing the superstructure with lightweight concrete can oftentimes allow the bridge rating to be upgraded to higher load capacities or higher traffic volumes. Furthermore, lightweight concrete can be used initially in a bridge deck to provide reduced weight and a lower modulus of elasticity, therefore lower cracking potential. The Kansas Department of Transportation is interested in the potential benefits of using lightweight aggregate concrete in Kansas bridge decks and prestressed bridge girders. This research project used three types of lightweight aggregate to develop lightweight concrete mixtures for a bridge deck and for prestressed bridge girders. Two of the lightweight aggregates were expanded shale obtained locally from the Buildex Company. One deposit was located in Marquette, Kansas, and the other in New Market, Missouri. The third lightweight aggregate source was expanded slate obtained from the Stalite Company in North Carolina. Aggregate properties including absorption, gradation, and L.A. Abrasion were evaluated. Over 150 lightweight concrete mixtures were created and tested and several mix design variables such as water-to-cement ratio, cement content, and coarse-to-fine aggregate ratio were evaluated. From these results, optimized bridge deck and optimized prestressed concrete mixtures were developed for each type of lightweight aggregate. Special concerns for lightweight aggregate concrete are addressed. These optimized concrete mixtures were then tested for KDOT acceptability standards for the concrete properties of compressive strength, tensile strength, modulus of elasticity, freeze-thaw resistance, permeability, alkali-silica reactivity, drying shrinkage, and autogenous shrinkage. All concrete mixtures performed satisfactorily according to KDOT standards. In addition, an internal curing effect due to the moisture content of the lightweight aggregate was observed during the autogenous shrinkage test.
Author: Arman Abdigaliyev
Author: Arman Abdigaliyev
Author: Jagan Mohan Rao V. V. Kanaparthi
Author: 
Author: Norbert J. Delatte
Author: Sarah Jo Grotheer
Author: Dola K. Erla
Author: Raghunandan V. Kadaba
Author: Sudharma Toyyeti
Author: Mang Tia
Author: Manoj Kotni Kumar