Effects of Construction Procedures and Material Properties on Low-Cracking High-Performance Concrete (LC-HPC) Bridge Decks

McLeod, Lindquist, Browning, and Darwin 2010 CBC

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EFFECTS OF CONSTRUCTION PROCEDURES AND MATERIAL PROPERTIES ON LOW-CRACKING HIGH-PERFORMANCE CONCRETE (LC-HPC) BRIDGE DECKS

Heather A. K. McLeod, PhD, PE, Kansas Department of Transportation, Topeka, KS

Will D. Lindquist, PhD, Trine University, Angola, IN JoAnn Browning, PhD, PE, University of Kansas, Lawrence, KS

David Darwin, PhD, PE, University of Kansas, Lawrence, KS ABSTRACT

Research dating to 1970 provides strong guidance on how to reduce cracking in bridge decks. This knowledge is being applied in a pooled-fund study with 19 state Departments of Transportation and the Federal Highway Administration to develop aggregate, concrete, and construction specifications for low-cracking high performance concrete (LC-HPC) bridge decks. In Phase I of the study, 20 bridge decks were constructed using a combination of best practices. Techniques to reduce cracking include a reduction in the cement paste content of the concrete while maintaining workability, finishability, and pumpability thorough the use of optimized aggregate gradations, limiting slump, maintaining adequate air content, deemphasizing the importance of high compressive strength and low concrete permeability, controlling the temperature of the concrete at the time of placement, minimizing evaporation during placement, improved curing, and reducing the rate of drying after curing is complete. The background and specifications are presented, along with a discussion of the effects of construction procedures and concrete properties on the level of cracking observed in 14 bridge decks constructed in Kansas. Crack densities are uniformly below densities observed in matching conventional bridge decks, and deck performance is clearly connected to the degree to which the LC-HPC specifications are met. Phase II of the study with the construction of 20 additional bridge decks is now underway.

Keywords: Cracking, Concrete bridge deck, Construction, Concrete temperature, Low paste content, Shrinkage cracks, Optimized aggregate, Curing


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INTRODUCTION

Cracks in bridge decks provide a direct path for water and deicing chemicals to enter the concrete, reach the reinforcing steel, induce or accelerate corrosion, and shorten the life of the deck. As shown in Fig. 1, measurements of chloride content in Kansas bridge decks taken at the level of the top reinforcing steel demonstrate that uncracked (solid) concrete can significantly slow the penetration of chlorides into the decks. In contrast, the measurements in cracked concrete (Fig. 2) clearly indicate that chlorides reach the top reinforcing steel in bridge decks within one year. Cracking in bridge decks, therefore, clearly provides a rapid mechanism (or path) for chlorides to enter the concrete, initiate corrosion, and significantly reduce the effectiveness of other techniques used to increase the life of a deck.

Fig. 1 Chloride contents measured at the level top reinforcement – off crack locations1

Fig. 2 Chloride contents measured at the level top reinforcement – on crack locations1

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BACKGROUND Research,2,3,4 some of which dates back nearly 40 years, including three detailed bridge deck survey studies1,5,6 performed by the University of Kansas, have investigated the causes of cracking in bridge decks and provide specific guidance on modifications in materials and construction techniques that will reduce the amount of cracking in bridge decks. Settlement cracking, formed in plastic concrete directly above and parallel to reinforcing steel due to settlement of the concrete around the bars, can be reduced with increased concrete cover for the top reinforcement, decreased bar size, and decreased concrete slump.7 Shrinkage cracking can be reduced by decreasing the volume of water and cement (paste), and maintaining air contents of about 6%. Increased compressive strength is associated with increased cracking.1,5,6,7 An optimized aggregate gradation can help provide adequate workability for concrete mix designs containing minimized paste contents,8,9 and workability can be enhanced using plasticizing admixtures. Increased compressive strength, normally associated with high-performance concrete, often has a negative impact on cracking.1,5,6 During construction, plastic shrinkage cracking increases as the rate of evaporation of water from the surface of the concrete increases. Differences in the concrete temperature and the girder temperature can lead to thermal shrinkage cracking, especially if the concrete temperature is significantly higher than the girder temperature. Even when plastic shrinkage cracking or thermal cracking is not specifically observed, the stresses induced can result in a greater risk of cracking at later ages as additional stresses are incurred, such as due to drying shrinkage. Construction techniques, such as minimizing the amount finishing, initiating wet curing immediately after finishing (onto the plastic concrete surface), controlling concrete temperatures, and increasing the length of the curing period can have a positive impact on the problem. In addition, Fig. 3 shows that in Kansas concrete decks cast in the 1990s crack significantly more than those cast in the 1980s. This observation can be attributed to many factors, including progressively finer gradations of portland cement (providing higher early strengths and increased shrinkage) as well as increased slump, and the use of pumps to place concrete on decks, requiring more paste and a higher slump. In spite of this accumulation of knowledge, only a small number of these findings have been used to implement changes in bridge deck design and construction procedures. In specific cases, on-site observations indicate that it is possible to develop nearly crack-free bridge decks, if “best practices” are followed. Even with these few successes, most bridge decks exhibit significant cracking, exposing the reinforcing steel to deicing chemicals and subsequent corrosion and increasing the degree of saturation, which increases the impact of freeze-thaw cycles. However, the current level of understanding offers the potential of constructing bridge decks with minimum cracking on a routine basis.


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Fig. 3 Mean crack density of bridges (age-corrected to 78 months and uncorrected) versus date of construction for monolithic bridge decks1

OBJECTIVES OF THE STUDY The purpose of the study, which has been underway since 2002, is to implement the most cost-effective techniques for improving bridge deck life through the reduction of cracking. The work involves cooperation between materials suppliers, contractors, and designers. The study is being completed in two phases: Phase I involves the implementation of traditional best practices to construct bridge decks with low cracking. Phase II extends the construction of 20 new bridge decks to include concrete mix designs with internal curing agents or shrinkage reducing admixtures in combination with supplemental cementitious materials. The following tasks have been used to achieve the objectives of the first phase of the study. 1. Develop a detailed plan to construct bridge decks with minimum cracking by incorporating “best practices” dealing with materials, construction procedures, and structural design. This task has involved cataloging available techniques and meeting with department of transportation personnel from multiple states, as well as other experts, to select the procedures to be used and the bridge types to which they will be applied. 2. Work with state DOTs, designers, contractors, inspectors, and material suppliers to modify designs, specifications, contracting procedures, construction techniques, and materials to obtain decks exhibiting minimal cracking. In this task, for example, specifications were altered to ensure that the concrete is fully consolidated, plastic shrinkage is minimized, and high-quality long-term curing is used. Concrete mixes with low cement contents and cements with low shrinkage characteristics have been evaluated for implementation in the specifications.

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3. Select and construct bridges using “best practices,” and educate contractors, materials suppliers, engineers, and inspectors in application of the techniques. Twenty bridges, 15 in northeast Kansas and five in other participating states, were selected for construction using the new techniques. Eighteen of the twenty bridges were ultimately constructed. Two were not constructed due to changes in construction scheduling. Researchers from the University of Kansas and state DOT personnel worked closely with contractors and materials suppliers to achieve the desired results. Pre-qualification of contractors included detailed presentations by the University of Kansas at pre-bid conferences to help educate and train engineers and contractors in implementing the “best-practices” identified in Tasks 1 and 2. 4. Carry out detailed crack surveys on the bridge decks, one, two, three, four, and five years after construction. The surveys are done using techniques developed at the University of Kansas that involve identifying and measuring all cracks visible on the upper surface of the bridge deck. 5. Correlate the cracking measured in Task 4 with the environmental and site conditions, construction techniques, design specifications and material properties and compare with earlier data. Similar data from participating states, where it exists, will be incorporated in the analysis. Final construction costs will be compared with potential benefits. 6. Document the results of the study. Final reports have been prepared from Phase I and disseminated to participating states regarding the findings of Tasks 1-5. Recommendations for further implementation and studies have been discussed in a final presentation to a committee of the participants. 7. Develop a training program to assist the participating states in implementing the findings of the study. The program has consisted of workshops held at the representative state DOT offices. In addition, a training video that features the background substantiating the specifications, the content of the specifications for low-cracking bridge decks, and experiences in the field has been developed and distributed to all participants. A technical committee, structured with one representative from each state providing funds, is overseeing the project. SPECIFICATIONS A construction specification based on the AASHTO LRFD Bridge Construction Specifications11 has been developed for low-cracking high performance concrete (LC-HPC) bridge decks. Special provisions for individual state DOTs are then developed based on these specifications and consultation with the University of Kansas. The emphasis of the research specifications can be divided into three general areas: materials specifications, placing and finishing procedures, and curing procedures. The entire construction process is evaluated prior to placement of the bridge deck through the construction of a qualification slab. The contractor must demonstrate the ability to handle, place, finish, and cure the optimized concrete mix 15 to 45 days prior to placing LC-HPC in the bridge


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deck. The qualification slab is at least 10 m (33 ft) long with the same width and thickness and the same reinforcement configuration as the actual deck. Cores are taken from the hardened qualification slab to assure that proper consolidation of the concrete has been attained. MATERIALS SPECIFICATIONS Previous research, including the three studies of bridge deck cracking in the State of Kansas,1,5,6 has led to a good understanding of how concrete material practices can influence the cracking tendencies of bridge decks. The cracking studies in Kansas included detailed surveys of bridge decks to produce digitized crack maps, which were then correlated with construction diaries to determine the primary influences for increased cracking in bridge decks. A primary focus of the material specifications is to reduce the portion of the mix that tends to shrink and crack, namely the cement paste. This is accomplished by requiring an optimized aggregate gradation (based on the Shilstone9 method), specifying a cement content between 296 and 320 kg/m3 (500 and 540 lb/yd3), and a water-cement ratio of 0.44 to 0.45. The result of this limitation is that the volume of the paste content of the concrete is kept below 25%. Other material specifications include air content (design range = 8% ± 1%, with absolute limits of 6.5 to 9.5%), a 25-mm (1-in.) maximum size aggregate, and a nominal slump of 35 to 75 mm (1½ to 3 in.), with a maximum of 100 mm (4 in.). A durable aggregate with a maximum absorption of 0.7% is required. Initial mix designs do not use mineral admixtures, but these are included in the scope for Phase II of the study. Because high concrete temperatures can lead to increased cracking, the specified concrete temperature prior to placement must be between 13o C and 21o C (55o F and 70o F) [10o C and 24o C (50o F and 75o F) with approval of the engineer]. In hot weather, this may require the use of chilled water and ice in the mix, injection of liquid nitrogen into the truck, shaded/cooled aggregate piles, or a combination of these strategies. The quality of the concrete mix is assured with a qualification batch, which is to be completed 35 days prior to the bridge deck placement, and must simulate the haul time to the job site. PLACING AND FINISHING PROCEDURES In general practice, pumping concrete requires an increase in the paste (water and cement) content to lubricate the pump, increasing the risk for shrinkage and cracking. Pumping is allowed if the contractor can demonstrate that the approved mix can be pumped. However, the lower paste content and limited slump specified for the concrete may limit the use of pumps to place the concrete in the field. In that case, conveyors or buckets must be used by the contractor. In the field, adequate placement rates have been maintained using conveyors and buckets. Consolidation is obtained by using gang-mounted vibrators that are lowered into the concrete at a 300-mm (12-in.) center-to-center spacing. Only minimal finishing is allowed, as excessive working of the concrete can cause increased quantities of cement paste to rise to the surface. A vibrating screed is preferred, although few are available in practice. In lieu of a vibrating screed, a drum roller screed is allowed. Tamping devices or other fixtures which may push coarse aggregate away from the surface of the concrete are not allowed. Final finishing with a bullfloat, pan drag, or burlap drag may follow the


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finishing equipment, but final texturing is provided by grinding and grooving the hardened concrete. Tining fresh concrete is not allowed. CURING PROCEDURES A major factor in obtaining a low-cracking concrete bridge deck is the use of proper curing procedures. This begins with the weather conditions. Wind speed and humidity are measured to estimate the evaporation rate, and if this exceeds 1.0 kg/m2/hr (0.2 lb/ft2/hr), the contractor must use measures, such as wind breaks and cooling the concrete, to provide suitable conditions for concrete placement. During delays longer than 10 minutes, all concrete that has been placed but not finished must be covered with pre-soaked burlap to protect the concrete from drying. Wet curing must begin within 10 minutes of concrete strike-off, and the surface is not allowed to dry between strike-off and the end of the curing period. Wet curing is initiated by placing the first layer of pre-soaked burlap onto the finished concrete surface within 10 minutes of strike-off (Fig. 4), followed by a second layer of pre-soaked burlap within 5 minutes. Misting hoses are used to keep the burlap from drying, and soaker hoses are placed on the burlap and running water supplied continuously once the concrete has set sufficiently for foot traffic to keep the entire LC-HPC surface continuously wet for the entire curing period. A white polyethylene film is placed over the soaker hoses to prevent rapid evaporation and reflect the sun. Regular inspection during the wet curing period is critical to assure that the concrete surface never dries. The wet-curing procedure is maintained for 14 days, at which time the absorptive materials are removed and a curing membrane is applied to the surface and left unmarred for 7 days to slow the initial drying rate.

Fig. 4 Placement of pre-soaked burlap within 10 minutes of strike-off


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Curing during cold weather requires extra precautions to reduce cracking caused by thermal stresses. In order to prevent cracking, the difference between the concrete and steel girder temperatures must be minimized. During the curing period, if the ambient air temperature is expected to drop below 5o C (40o F), protective measures must be taken to maintain the temperature of both the concrete and the girders between 5º C (40º F) and 24º C (75º F). This may include using straw, blankets, or extra burlap on the concrete, and enclosing the area under the deck to girders and heating. The air surrounding the girders is heated to be as close as possible to the temperature of the concrete and between 5o C (40o F) and 24º C (75º F). Similar protective measures must be taken when the ambient air temperature is expected to drop more than 14° C (25° F) below the placement temperature of the concrete during the first 24 hours after placement. Heating may be discontinued after 72 hours if the time of curing is lengthened to account for periods when the ambient air temperature drops below 5o C (40o F) during the remainder of the curing period. The additional curing time, at a minimum ambient air temperature of 10º C (50º F), must match the period during the original curing period in which the air temperature is below 5º C (40º F). PRELIMINARY RESULTS The success of LC-HPC in bridge decks is illustrated by the crack surveys that have been completed in the months and years following construction. Figure 5 compares bridge deck crack densities, in units of linear meters of crack per square meters of bridge deck, versus deck age in months.12,13 Data points that are connected by lines represent bridge decks that have been visited multiple times. The figure shows the results of previous crack surveys of monolithic bridge decks across the state of Kansas at various ages (open diamonds) and the current surveys for both control and LC-HPC decks. As shown in the figure, early-age cracking in the LC-HPC decks is less than 10% of that found in representative control bridge decks. The relatively low slope of the lines connecting data points from different points in time for decks older than 48 months also indicates that by controlling early age-cracking, the amount of cracking at later ages will also remain low. This trend will continue to be evaluated in the coming years. CONSTRUCTION TECHNIQUES Construction methods can significantly affect the cracking tendency of concrete bridge decks, including environmental site conditions, placement method, consolidation, finishing, and curing. Construction without consideration of environmental conditions can lead to extreme exposure conditions and can negatively impact cracking. Increasing the concrete paste content of a mixture to ease the pumping and finishing can increase the risk of drying shrinkage cracking. Inadequate consolidation can increase settlement cracking. Overfinishing works additional cement paste to the surface and can delay the initiation of curing, both of which will increase the risk for plastic shrinkage cracking. Overfinishing may also lead to durability problems such as scaling. In fact, attempting to obtain a “perfect” deck finish significantly increases the risk for plastic shrinkage cracking. Controlling concrete temperatures and providing immediate wet curing can help to control thermal cracking. Methods of protecting the concrete and the finished deck and girders during cold weather (placement and curing methods) may also significantly impact cracking on the bridge deck, if not executed properly. Overheating or removing heating


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without allowing the temperatures to decrease slowly can cause temperature differentials that can lead to thermal cracking. If heaters are not properly vented, carbonation can also be a problem. Overall, the construction methods used in constructing a bridge deck impact cracking, several of which are discussed.

Fig. 5 Results of crack surveys from LC-HPC and conventional (Control and Lindquist et al.1) bridge decks

Site Conditions Site conditions during placement, such as air temperature and wind speed, are generally recognized as having the potential for significant impact on bridge deck cracking, particularly for thermal cracking and plastic shrinkage cracking. Air temperature, wind speed, relative humidity, and concrete temperature contribute to the rate of evaporation of water from the concrete, increasing the potential for plastic shrinkage cracking. Casting warm concrete in cool weather increases the risk for high evaporation conditions because the concrete heats the air directly above the concrete surface (dropping the relative humidity and allowing increased amounts of concrete moisture to evaporate into the warm air); the warm air is quickly replaced by cold dry air, and the cycle is continuously repeated. Elevated amounts of cracking in monolithic bridge decks corresponds with increasing high (maximum) air temperature on the day of placement.1 The preliminary results for this study indicate that this trend is halted or even reversed for LC-HPC construction. As shown in Fig. 6, for standard monolithic decks cast in Kansas, cracking increases from 0.15 to 0.44 m/m2 as the high air temperature during the day of placement increases from 5° to 35° C (41° to 95° F).12 In contrast, the data for LC-HPC decks indicates a slight decrease in cracking with an increase in high air temperature.

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Fig. 6 Average Crack Density (age-corrected to 78 months) versus High Air Temperature for monolithic and LC-HPC decks12

Consolidation For LC-HPC construction, consolidation is performed using gang-mounted vibrators, as shown in Fig. 7. At locations where the finishing bridge and gang vibrators could not reach, hand-held vibrators were used. For the hand-held vibrators, the insertion points, as seen in Fig. 8, were generally not as close as required by the specifications. In addition, if vibrators are removed prematurely (not left in the concrete long enough) or removed too quickly, as shown in Fig. 9,

Fig. 7 Gang vibrator system used for consolidation12

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voids are left in the concrete, resulting in inadequate consolidation, and locations that do not contain coarse aggregate particles – all leading to increased risk for settlement cracking.

Fig. 8 Insertion points for hand held vibrators are farther apart than for gang vibrators12

Fig. 9 Coarse aggregate particles and a consolidation lip at the locations of vibrator insertion points indicate inadequate consolidation12


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Qualification Slab A qualification slab, as shown in Fig. 10, is constructed prior to placement of the bridge deck. The purpose is for the contractor to demonstrate the ability to place, finish, and cure the LC-HPC bridge deck according to the specifications. The qualification slab helps ensure that there are no “surprises” during the construction of the bridge deck. As a result, the contractor’s first experience with LC-HPC construction is on a qualification slab, not on the deck, where the performance is most critical. The crews gain hands-on experience and learn the new techniques. This helps get the “kinks” out of the process for the contractor, concrete supplier, inspectors, and owner before the day that the deck is placed.

At the end of the qualification slab for LC-HPC Bridge 7, the construction engineer said, “Today proved the value of the trial [qualification] slab. We will be able to visually see how much the contractor learned from the beginning to the end of the trial slab.”12 During the post-construction meeting, the concrete supplier indicated that the qualification slab was worthwhile to help make the changes necessary and check how the air content changed through the pump.

Fig. 10 Qualification slab constructed prior to LC-HPC bridge deck placement. MATERIALS For the parameters considered, crack density results are presented at the time of the crack surveys (uncorrected), as well as projected crack densities (age-corrected) representing the expected level of cracking at an age of 78 months (6.5 years). The projected values are obtained using the average rate of increasing crack density that was determined for monolithic and silica fume overlay bridge decks in previous studies.1, 12, 13


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Paste Content The percentage volume of water and cement in the concrete mixture is the constituent that undergoes the majority of the shrinkage so it comes as no surprise that this volume has a strong influence on the level of cracking observed in bridge decks. The average age-corrected crack density (and uncorrected) is shown as a function of paste volume in Fig. 11. The highest crack densities occur for placements with the largest volume of cement paste.

Fig. 11 Average crack density (age-corrected and uncorrected) versus percent volume of water and cement for monolithic placements13

Compressive Strength The average age-corrected (and uncorrected) crack density for individual placements is shown as a function of compressive strength in Fig. 12. The relationship between compressive strength and cracking is clear for both the LC-HPC placements and the conventional monolithic placements. Cracking increases as compressive strength increases. ADHERENCE TO THE SPECIFICATIONS Deck performance is clearly connected to the degree to which the specification requirements are met, and observations during construction of Bridge 14 (in three placements) highlight the need for adherence to construction and materials specifications. Although this bridge was intended to be LC-HPC construction, the specifications were not appropriately followed, as described next, and thus negatively impacted the cracking performance of this bridge. Preliminary crack surveys indicate that this bridge deck has significantly higher cracking than LC-HPC bridges.

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Fig. 12 Average crack density (age-corrected and uncorrected) versus measured air content for monolithic placements13

Finishing and Burlap Placement As discussed previously, only minimal finishing is allowed for LC-HPC construction, as excessive working of the concrete can cause increased quantities of cement paste to rise to the surface. The use of any type of finishing aid is not allowed for LC-HPC construction. Water from fogging equipment, curing or any other source may not be worked into the surface of the deck. For Bridge 14, the contractor spent considerable effort finishing the deck, using bullfloats and hand floats to provide a smooth finish, and the deck bordered on being overfinished. In addition, on multiple occasions, and against the instructions of the owner, a finishing aid was used, as well as ponded water and fogging water was worked into the surface of the deck. Burlap placement for Bridge 14 was very slow. The contractor achieved placement of burlap within the 10-minute requirement only one time on 61 stations timed during construction. At times, the time to burlap placement ranged from 40 to 70 minutes, leaving the finished concrete surface exposed to drying conditions. Slump and Air Content For Bridge 14, the specifications required a design slump of 1½ to 3 in., but allowed a 4 in. (100 mm) slump to be placed during construction. For each of the three placements, the allowed slump was 5.75 in. (145 mm) or greater, with the average slump for the deck exceeding 4 in. (100 mm). Test results also indicated that a significant portion of the concrete placed in Bridge 14 had a higher air content than allowed by the specifications. For placements 2 and 3, the average air content for all tests during the placement exceeded 9.5%.

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Bridge 14 did not qualify as LC-HPC construction and preliminary crack density data show that it contains significant cracking. PHASE II FOR LC-HPC BRIDGES The second phase of the project is currently underway and includes the construction of 20 additional LC-HPC bridge decks. Phase II seeks to expand the scope of implementing LC-HPC construction from traditional best practices, to implementing LC-HPC mix designs containing mineral admixtures, shrinkage reducing admixtures, and aggregate to provide internal curing. Data indicates that drying shrinkage can be reduced significantly when internal curing is used with mixtures containing ground granulated blast furnace slag used as a partial replacement for portland cement. Internal curing may be provided by fully or partially saturated limestone with 2.5 to 3% absorption or by partial replacement of coarse aggregate with pre-saturated lightweight aggregate. Silica fume and fly ash are also under investigation for their benefit to permeability (silica fume) and sustainability (fly ash). All LC-HPC mixtures are evaluated for durability, constructability, and their potential to reduce cracking before implementation in the field. Continued emphasis on construction techniques will include controlling plastic concrete properties, especially slump. SUMMARY The construction of bridges and bridge decks requires significant resources from federal, state, and city governments and their respective transportation agencies. Previous research has detailed specific modifications to construction procedures, materials, and design details that can significantly reduce the amount of cracking in bridge decks. This project shows how a comprehensive strategy to implement industry best practices in the design and construction of bridge decks leads to greatly reduced cracking and, ultimately, increased the life for bridge decks. ACKNOWLEDGEMENTS The research reported in this paper was supported through a Pooled-Fund study supported by the Departments of Transportation of the states of Kansas (lead state), Colorado, Delaware, Idaho, Indiana, Michigan, Minnesota, Mississippi, Missouri, Montana, New Hampshire, New York, North Dakota, Ohio, Oklahoma, South Dakota, Texas, Wisconsin, and Wyoming, the Federal Highway Administration, and the City of Overland Park, Kansas, BASF Construction Chemicals, and the Silica Fume Association.


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REFERENCES 1. Lindquist, W. D., Darwin, D., and Browning, J., “Cracking and Chloride Content in

Reinforced Concrete Bridge Decks,” SM Report No. 78, University of Kansas Center for Research, Inc., Lawrence, Kansas, 2005, 453 pp.

2. Durability of Concrete Bridge Decks – A Cooperative Study, Final Report, The state highway departments of California, Illinois, Kansas, Michigan, Minnesota, Missouri, New Jersey, Ohio, Texas, and Virginia; the Bureau of Public Roads; and Portland Cement Association, 1970, 35 pp.

3. Krauss, P. D., and Rogalla, E. A., “Transverse Cracking in Newly Constructed Bridge Decks,” National Cooperative Highway Research Program Report 380, Transportation Research Board, Washington, D.C., 1996, 126 pp.

4. Eppers, L., French, C., and Hajjar, J. F., “Transverse Cracking in Bridge Decks: Field Study,” Minnesota Department of Transportation, Saint Paul, MN, 1998, 195 pp.

5. Schmitt, T. R., and Darwin, D., (1999). “Effect of Material Properties on Cracking in Bridge Decks,” Journal of Bridge Engineering, ASCE, Feb., V. 4, No. 1, 1999, pp. 8-13.

6. Miller, G. G., and Darwin, D., “Performance and Constructability of Silica Fume Bridge Deck Overlays,” SM Report No. 57, University of Kansas Center for Research, Inc., Lawrence, Kansas, 2000, 423 pp.

7. Dakhil, F. H., Cady, P. D., and Carrier, R. E., “Cracking of Fresh Concrete as Related to Reinforcement,” ACI Journal, Proceedings, V. 72, No. 8, Aug. 1975, pp. 421-428.

8. Lindquist, W., Darwin, D., Browning, J., McLeod, H. A. K., Reynolds, D., “KU Mix Method of Aggregate Optimization,” ACI Materials Journal, in review.

9. Shilstone, J. M. Sr., “Concrete Mixture Optimization,” Concrete International, V. 12, No. 6, June 1990, pp. 33-38.

10. Poppe, J. B., “Factors Affecting the Durability of Concrete Bridge Decks: Summary Final Report,” Report No. FHWA /CA/SD-81/2, California Department of Transportation, Division of Transportation Facilities Design, Sacramento, CA, 1981, 61 pp.

11. American Association of State Transportation and Highway Officials (2004). AASHTO LRFD Bridge Construction Specifications, 2nd Edition, 2004, 620 pp.

12. McLeod, H. A. K., Darwin, D., and Browning, J, “Development and Construction of Low-Cracking High-Performance Concrete (LC-HPC) Bridge Decks: Construction Methods, Specifications, and Resistance to Chloride Ion Penetration,” SM Report No. 94, University of Kansas Center for Research, Inc., Lawrence, Kansas, 2009, 815 pp.

13. Lindquist, W. D., Darwin, D., and Browning, J., “Development and Construction of Low-Cracking High-Performance Concrete (LC-HPC) Bridge Decks: Free Shrinkage, Mixture Optimization, and Concrete Production,” SM Report No. 92, University of Kansas Center for Research, Inc., Lawrence, Kansas, 2008, 504 pp.

Documents

Effects of Construction Procedures and Material Properties on Low-Cracking High-Performance Concrete (LC-HPC) Bridge Decks