Sanders Peyton Hale TRB 2006 August 5 2006 revised

Sanders, Peyton, Hale Investigating the Causes of Bridge Deck Cracking August 1, 2006 Word Count: 7340 Steve W Peyton, Bridge Engineer Arkansas State Highway and Transportation Department P.O Box 2261 Little Rock, AR 72203 Tel: (501) 569-2000 Fax: (501)-569-2400 steven.peyton@arkansashighways.com Chris L Sanders, Graduate Research Assistant Department of Civil Engineering University of Arkansas 4190 Bell Engineering Center Fayetteville, AR 72701 Tel: (479) 575-2970 Fax: (479) 575-7168 cls20@uark.edu W Micah Hale, Assistant Professor Department of Civil Engineering University of Arkansas 4190 Bell Engineering Center Fayetteville, AR 72701 Tel: (479) 575-2970 Fax: (479) 575-7168 micah@uark.edu ABSTRACT A research program conducted by the University of Arkansas along with the Arkansas State Highway and Transportation Department investigated the concrete properties, curing regimens, and cracking density of five bridge decks cast in Arkansas Concrete was sampled from five bridge decks under construction in the summer of 2005 The fresh and hardened concrete properties were measured for all the bridge decks The curing regimens for the bridge decks were also documented After construction, the research team returned to each bridge to investigate and measure the amount of cracking The findings from the research showed that there were many factors that led to bridge deck cracking and there was difficulty determining if there was a single factor that led to the cracking Some of those factors included low one day compressive strengths, delayed curing, and deck movement during construction Sanders, Peyton, Hale INTRODUCTION Many factors contribute to cracking in concrete bridge decks Some of these factors include structural design, material properties, mixture proportioning, and construction and curing practices During the summer of 2005, five bridge decks were examined to determine which of these factors contributed to bridge deck cracking The research focused on the construction practices, curing regimens, and concrete properties BACKGROUND Permeability, durability, and compressive strength are three concrete properties that play a significant role in the overall bridge deck performance All three of these properties are affected by concrete mixture proportioning and construction practices These concrete properties have been proven as good indicators of bridge deck concrete performance Permeability is the ability of concrete to resist penetration by water or other substances Chloride penetration is a major concern in bridge decks (1) Low permeability concrete can generally be obtained through a low water to cementious material ratio (w/cm) Much research has found that permeability was proportional to w/cm Low permeability concrete provides greater protection against reinforcement corrosion (2) Decks that had high permeability also experienced severe cracking; therefore, permeability might be used as an indicator for predicting the cracking potential of concrete (3) NCHRP Synthesis 333 recommends bridge deck concrete to have permeability, per AASHTO T 277, in the range of 1,500 and 2,500 coulombs to enhance the performance of bridge deck concrete (1) Concrete durability is the ability to resist weathering action, chemical attack, abrasion, and any other process of deterioration ACI Committee 201 (Guide to Durable Concrete) recommends that bridge decks exposed to deicing salts have a maximum w/cm of 0.45 and an average air content of 6% for a nominal maximum size aggregate of one inch (2) NCHRP Synthesis 333 recommends the use of concrete with w/cm between 0.40 and 0.45 to enhance the bridge deck performance (1) As compressive strength increases, creep decreases at a higher rate than the rate of increase of tensile strength This is one of the reasons high strength concretes, which have higher tensile strengths than regular concrete, experience more cracking (3,4) Cracking tends to increase with compressive strengths, which is most likely related to increases in cement content and paste volume This has been shown to be a direct relationship in separate comparisons (5) Many agencies have suggested that the trend of increasing 28-day compressive strengths has led to increased cracking Some specified mixtures can achieve 28-day strengths in three to seven days Compressive strengths for bridge decks should be based on later age compressive strengths, such as 56- or 90-day compressive strength so low heat of hydration cement and supplementary cementing materials can be incorporated into bridge decks without violating strength requirements (6) Also, early age strengths of concrete should be controlled carefully in order to avoid early deck cracking (7) Finer modern cements typically have one-day compressive strengths near 45 percent of the 28-day strengths Cement manufactured in the mid1940s had one-day compressive strengths of only 11 percent of the 28-day strength (6) Sanders, Peyton, Hale AASHTO and AHTD require a minimum 28-day compressive strength of 4,000 psi for bridge deck concrete (8,9) TESTING PROGRAM The research team sampled concrete from five bridge decks in the state of Arkansas from June 2005 to September 2005 The quantity of concrete placed at the bridge decks ranged from approximately 120 to 400 cubic yards The fresh concrete tests performed were slump (AASHTO T 119), unit weight (AASHTO T 121), air content (AASHTO T 152), and concrete temperature (AASHTO T 309) For the first three decks, the research team performed all the fresh concrete tests at three different locations (beginning, middle, and end regions) on the bridge deck and cast 4” x 8” cylinders for compressive strength tests at those same locations At the middle sampling location, eight 4” x 8” cylinders (for rapid chloride ion penetrability (RCIP) tests), four freeze-thaw specimens (3” x 3” x 16”), and four unrestrained shrinkage specimens (4” x 4” x 11.25”) were cast in addition to the compressive strength cylinders The last two decks were much smaller, and therefore the research team performed the fresh concrete tests at only two locations on the bridge decks Compressive strength cylinders were also cast at two locations on the smaller decks The compressive strength cylinders (AASHTO T 22), freeze/thaw specimens (AASHTO T 161A), and unrestrained specimens (AASHTO T 160) cast at the first bridge deck were transported the morning after the deck placement, therefore complying with AASHTO T 23 However, for the four other bridge decks, the majority of the samples were transportated before the eight hour minimum time limit These samples were transported in the back of a full-size truck in containers that were placed on approximately three inches of soft foam to reduce vibration After the initial 24 hours, the molds were removed and all specimens were air cured in an environmental chamber at 73°F and approximately 50 % relative humidity The research team measured compressive strength at 1, 7, 28, and 56 days of age Three cylinders were tested on each of these days The research team measured length change at 1, 4, 7, 28, 56, and 112 days of age The research team tested RCIP at 28 and 90 days of age, and freezing and thawing testing began at 14 days of age Manual Crack Mapping The process used to assess bridge deck cracking was similar to that used by AHTD Research Section personnel in a previous bridge deck study 13 The first step in the mapping process is typically an initial examination of the entire bridge deck to locate the areas most affected by cracking This is then the survey area It is generally limited to 100 ft in length unless the additional length would better represent the distress level of the deck as a whole Traffic control was provided by two AHTD personnel using a simple flagged lane closure with traffic cones along the centerline to keep motorists out of the survey area The actual mapping of distress in the survey section began with team members laying out a 100 ft tape measure along the lane edge This provided longitudinal stationing for the map A 25 ft tape measure was used to measure transversely from the Sanders, Peyton, Hale lane edges Cracks were then visually located and documented The length and location of the cracks were measured and recorded, along with orientation and approximate widths of the cracks, on a prepared form with a grid representing the survey section The widths of the cracks were measured with a crack comparator card AHTD Specifications for Class S(AE) Concrete Concrete used in bridge decks in Arkansas are classified as Class S(AE) concrete (AE for air entrained) For Class S(AE) concrete, AHTD requires a minimum 28-day compressive strength of 4000 psi, a slump of to in., and an air content of ± percent AHTD also requires Class S(AE) concrete mixtures have a maximum w/cm of 0.44, a minimum total cementitious material content of 611 lb/ yd 3, and a coarse aggregate meeting either the AHTD Standard Gradation or the AASHTO M43 #57 Gradation AHTD allows the use of fly ash and slag cement in bridge decks Fly ash can either be Class C or F, with no mixing of the two The maximum fly ash replacement rate is 20% by weight, and the maximum slag replacement rate is 25% by weight If both materials are used, the maximum replacement rate is 20%, by weight, for both materials AHTD specifications allow the use of several different materials for concrete curing Burlap-polyethylene sheeting, polyethylene sheeting, copolymer/synthetic blanket, membrane curing compounds, and other materials that meet AASHTO M 171 are allowed AHTD specifications require that the bridge deck have curing compound applied be covered immediately after finishing, be covered using mats or blankets as a final cure and that it remains covered for at least days During these days, the curing materials must be kept continuously wet (except for membrane curing) 802.17(b) Application The exposed concrete, immediately after finishing, shall be covered with one of the curing materials listed above and shall be kept continuously and thoroughly wet for a period of not less than days after the concrete is placed Membrane curing does not require the application of additional moisture, except as required for bridge roadway surfaces All Class B concrete shall be cured by free moisture Water curing shall be provided for all exposed surfaces for a period of 14 days Membrane curing compound shall not be used on surfaces requiring a Class finish Clear membrane curing compound shall be used as an interim cure for concrete bridge roadway surfaces and shall be applied immediately after final finishing Final curing of bridge decks shall be by mats or blankets and shall be begun immediately after completing the surface test specified in Subsection 802.20(c) The mats or blankets shall be kept continuously and thoroughly wet for a period of days after the concrete is placed Sanders, Peyton, Hale AHTD allows the contractors to the option of continuous pours for bridge decks If the contractors choose this option, the concrete must remain plastic during the entire length of the pour Rather than casting the negative positive moment regions of the bridge deck first then followed by the positive negative moment regions, most contractors are choosing continuous casting or pours to spend speed up the construction process In this research program, all decks sampled were continuous pours Concrete Mixture Proportions The concrete mixture proportions for the five bridge decks are shown below in Table As previously stated, AHTD requires a maximum w/cm of 0.44, a total cementitious material content of 611 lb/yd3, and an air content of 6±2% for bridge deck concrete All contractors chose to use the least amount of cementitous material required (611 lb/yd 3) and three contractors chose to use fly ash (at replacement rates ranging from 15 to 20%) Three of the five concrete mixtures had the maximum w/cm of 0.44, and the lowest w/cm used was 0.41 A high range water reducer (HRWR) was used in the third bridge deck, which had the lowest w/cm The coarse aggregate content was different for all but two of the decks AHTD does not specify a coarse aggregate content Fly ash was the only SCM used in the bridge decks TABLE Concrete Mixture Proportions Materials Bridge Decks Cement (lb/yd3) 519 519 489 611 611 Fly Ash (lb/yd3) 92 92 122 0 Fly Ash (%) 15 15 20 0 1670 1670 1940 1722 1749 Coarse Agg (lb/yd3) Coarse Aggregate Type Limestone Limestone River Gr Limestone River Gr Fine Aggregate (lb/yd3) 1293 1293 978 1273 1112 Water (lb/yd3) 269 269 251 269 298 w/cm 0.44 0.44 0.41 0.43 0.44 AEA Dosage (fl oz/cwt) 0.75 0.70 1.00 0.50 0.65 BRIDGE SPECIFICS As previously stated the research team sampled concrete from five bridge decks from June 2005 to September 2005 In addition to concrete properties, the researchers also documented the curing procedures and measured the cracking in each bridge deck Each Sanders, Peyton, Hale bridge deck is discussed in more detail in the following paragraphs The air temperature, relative humidity, and curing procedures are summarized for all decks and shown in Table Bridge Deck The first bridge deck visited is an interstate overpass The bridge deck was cast in the middle of June, and concrete placement began at 5:45 AM The bridge is 272 ft long and 43 ft wide and is a span plate girder bridge with spans of 149 ft and 123 ft The total quantity of concrete used was 331 yards and the deck was a continuous pour Like most bridge decks visited, the concrete was pumped up to the deck One construction worker with a commercial pressure washer fogged the concrete in the area of placement The concrete was then screeded, floated with a pan attached to the finishing machine, and then manually tined with a rake Finally, a curing compound was applied and then the deck was covered with a plastic/cotton matcotton mat, burlap, and plastic sheeting Bridge Deck The second bridge deck visited was an interstate bridge overpass The deck was cast in the middle of July and concrete placement began at 9:00 PM The overpass bridge was built using staged construction and the portion cast on this date is 330 ft long and 32 ft in wide and is part of a span curved plate girder unit The total quantity of concrete used was 330 yards and the deck was a continuous pour The concrete was pumped up to the deck One construction worker fogged the concrete at the surface near the finishing machine (prior to floating) The concrete was screeded and pan floated which was attached to the finishing machine The concrete was then bull floated with a 10 ft rounded float, and then manually tined with a rake The concrete was then sprayed with a curing compound and later covered with polyburlap for final cure Bridge Deck The third deck was a large city bridge that spanned a river The placement consisted of 400 yards of concrete and was a continuous pour The deck was cast in late August at 3:15 AM The plate girder bridge spans 367 ft with spans of 113, 141, and 113 ft The bridge deck is 43 ft wide The concrete was pumped, screeded with the finishing machine, floated with a pan attached to the finishing machine, bull floated, and then tined with a finned float Like the previous decks, one construction worker fogged the concrete near the finishing machine using a pressure washer The concrete was then sprayed with curing compound and later covered with polyburlap Bridge Deck Sanders, Peyton, Hale The fourth bridge deck was a state highway bridge that spanned a drainage ditch The bridge was placed in early September The three three-span bridge was a steel girder, wsection with spans of 38, 48, and 38 ft The bridge deck was 33 ft wide The placement consisted of a 117 yard continuous pour The concrete was pumped, screeded with the finishing machine, floated with a pan and dragged with burlap that were both attached to the finishing machine It was then tined with a rake, sprayed with curing compound, and later covered with polyburlap Bridge Deck The final bridge deck is a US highway spanning a small creek The bridge deck was placed in late September The deck was a 171 yard continuous pour placement The concrete was pumped, screeded with the finishing machine, floated with a pan attached to the finishing machine The deck was bull floated with a 10 ft rounded float, and then manually dragged with burlap It was then tined with a rake, sprayed with curing compound, and later covered with polyburlap TABLE Summary of Observations for All Decks1 Air Time to Size of Ave Bridge Time of Temp Curing Placement R H Deck Placement Range Compound (yd3) (%) (°F) Application 5:45 AM1 331 68-95 57 0.5-1 hr 12:20 PM 9:05 PM2 289 89-83 72 hr 3:05 AM 3:15 AM3 400 76-95 69 hr 12:20 PM 6:00 AM4 117 67-94 53 hr 10:15 AM 7:05 AM5 171 71-96 53 2.5 hr 10:40 AM Times are from the end of the placement Time to Final Cure1 Amount of Cracking ft/ft2 15.5 hr 0.315 7.00 hr 0.012 3.50 hr 0.1125 5.75 hr 0.0062 5.00 hr 0.051 RESULTS AND DISCUSSION Crack Mapping After the bridge decks were sampled, each deck was revisited to assess cracking For Bridge Deck 1, cracks were mapped on 4/5/06 after the bridge was open to traffic and Sanders, Peyton, Hale after the contractor had sealed larger cracks at some time prior to opening The researchers attempted to map all cracks in 12 by 100 ft section of south bound lane, but after measuring 40 ft of the 12 ft wide section, cracking became too small and random to effectively map A 10 ft by 12 ft sub-area was measured as a representative sample From visual estimation, the density was approximately the same as the representative sample for the remainder of original 100 foot section, although it lessened some in last 15 ft The cracks ranged from in to 48 ft in length and from less than 0.005 in to 0.024 in in width The cracks were a mix of transverse and longitudinal cracks with diagonal connecting cracks Long lines of cracking in the wheel path of the lanes were observed Also, cracks were concentrated over the center support (near the middle sampling location) of the deck This could possibly be due to a combination of vibrations from traffic passing under the bridge (which were noticeable) and low compressive strengths (at least up to days) at this section Bridge Deck was revisited on 8/1/05 The visible cracks were measured for the whole pour The cracks ranged from in to 17 ft in length and 0.002 to 0.016 in in width The cracks were mostly transverse and fairly heavy in the positive moment section The flexural cracks were located mainly near the piers and the plastic shrinkage cracks were located near the low gutter (the downhill side of the deck) Large amounts of paste were brought down to this side during construction using a highway screed High amounts of paste might have contributed to increased shrinkage in that area Bridge Deck was revisited on 1/27/06 The research team measured the cracking in a 12 ft by 100 ft section of the west bound lane The cracks ranged from ft to 12 ft in length and were less than 0.007 in wide The cracks were almost exclusively transverse cracks that started and stopped at similar points in the cross section (near beam lines) Bridge Deck was revisited on 2/9/06 The research team measured cracking in a 12 ft by 100 ft section of the deck There was very little cracking in the deck The cracks ranged from in to ft in length and 0.002 to 0.010 in in width Bridge Deck was mapped on 2/10/06 The cracks were measured over a 12 ft by 65 ft section The cracks were ft to ft in length and were 0.002 to 0.007 in wide There were some cracks that were to ft long and were at 45 ◦ angles to the intermediate bents Fresh Concrete Data As stated in the Testing Program, the fresh concrete properties were measured in two or three random locations (determined by AHTD) for each bridge deck If the bridge deck was large enough, the sampling locations were typically at the beginning, middle, and ends of the bridge deck The results from all the fresh concrete tests, the amount of cracking, and the AHTD specifications for each property are shown in Table From Table 3, one can see that the four of the five bridge decks had slumps that exceeded AHTD specifications in at least one location Bridge Deck was the only deck where all slumps fell within the to inch specification For the air content, three of the five bridge decks had measured air contents that did not meet AHTD specifications Only two bridge decks had fresh concrete temperatures that were greater than that allowed by AHTD Sanders, Peyton, Hale The final fresh concrete properties shown in Table are the calculated and measured unit weights The calculated unit weights are based of off the concrete mixture proportion used by the concrete supplier and assuming a fresh concrete air content of 6% The differences between calculated and measured unit weights ranged from a low of lb/ft3 to a high of lb/ft3 These differences between calculated and measured unit weights could be attributed to the addition of extra mixing water or to higher or lower than expected air contents In an attempt to determine of there were any relationships between the fresh concrete properties and crack density, the average slump, air content, measured unit weights, differences between measured and calculated unit weights, and concrete temperature were plotted versus the crack density Each bridge deck was ranked by each concrete property and assigned a ranking For example, Bridge Deck had an average slump of 3.17 inches which was the lowest average slump of the five decks, and therefore it received a ranking of “1” Likewise, Bridge Deck had the greatest average slump (7.125 inches) and received a ranking of “5” Shown in the Figure are the rankings for each fresh concrete property and crack density The graph shows that Bridge Deck 1, which had the highest crack density of 0.315 ft/ft 2, did not have the greatest value for any of the fresh concrete properties Bridge Deck had the second highest air content, third highest concrete temperature, fourth highest unit weight, and was ranked last in unit weight difference and slump For the concrete properties measured and bridge decks samples, there was no correlation between fresh concrete properties and crack density TABLE Fresh Concrete Properties Bridge Deck AHTD Specifications Slump (in) Air Content (%) 3.50 3.25 2.75 4.50 7.25 2.50 6.25 3.50 5.00 8.25 6.00 6.00 3.50 5.8 6.3 4.9 3.8 3.5 2.2 3.2 4.6 5.0 9.2 8.7 5.7 4.8 1-4 4-8 Calculated Unit Wt (lb/ft3) Measured Unit Wt (lb/ft3) 140 143 141 145 136 138 141 144 83 89 90 95 92 95 92 83 95 73 81 80 86 None 40°-90° 140 140 141 139 None Concrete Amount of Temperature Cracking (°F) ft/ft2 148 146 149 144 0.315 0.012 0.1125 0.0062 0.051 Sanders, Peyton, Hale 10 FIGURE Fresh concrete properties and crack density Hardened Concrete Properties The results from the compressive strength tests are shown in Table Three cylinders for compressive strength testing were cast from either two or three random locations (as determined by AHTD) in each bridge deck The amount of cracking is also shown for each bridge deck in Table For all decks, the contractors opted to pour each deck continuous, which by AHTD specifications, requires that all the concrete remain in a plastic state until concrete placement is finished Because of this reason, a set retarder was used in all decks The first bridge deck that was visited (Bridge Deck 1) had the lowest one day strengths The first and last sampling location had a one day compressive strength of approximately 300 psi while the middle sampling location had a one day compressive strength of 60 psi At two days of age, cylinders that were sampled from the first and middle locations of the bridge deck were tested These tests showed that the first location had gained over 2000 psi in 24 hours, but the middle section was still much lower (a compressive strength of 130 psi) By 28 days and 56 days of age, the middle section had reached similar strengths as the first and last sections of the bridge However, the research team did observe several transverse cracks in the center section of the Bridge Deck These cracks could be the result of the low compressive strengths of the middle location and the corresponding higher compressive strengths of the surrounding regions, but one cannot be certain due to the limited number of sampling locations The only other bridge deck to have large variations in compressive strength was Bridge Deck This deck was a smaller pour and due to time constraints only a limited Sanders, Peyton, Hale 11 number of cylinders were sampled from the last portion of the deck As seen in Table 4, the compressive strengths at one and 28 days of age for the last section of the deck were much higher than the first two sections (over 2000 psi at one day and over 4000 psi at 28 days) However, unlike the Bridge Deck 1, the large variation in compressive strength did not appear to contribute to bridge deck cracking For this particular bridge deck, the concrete supplier was having problems with the air content For the first two sections the air contents were at or near 9%, and efforts were being made to lower the air contents The researchers believe that the air content was indeed lower for the last section, which resulted in the higher compressive strengths TABLE Compressive Strength Results1 Bridge Deck Day Day Day 28 Day 2590 6680 130 6370 5750 7540 3420 5100 5070 2770 4530 5050 3570 5780 5830 1480 3670 4400 2140 3590 4190 1940 3830 4710 2350 3780 4940 2860 4430 5520 4730 9120 2960 4010 4660 3630 4410 5330 For each deck, each row represents one sampling location 340 60 320 - 56 Day 6850 7000 7950 5840 5260 6930 4640 4530 4950 4980 5560 4370 5710 Amount of Cracking ft/ft2 0.315 0.012 0.1125 0.0062 0.051 The remaining hardened concrete properties are shown in Table These properties include permeability, durability factors, and 112 day drying shrinkage The permeability (measured by the RCIP test) was measured at 28 and 90 days of age ASTM and AASHTO classify bridge decks with passing between 2000 and 4000 coulombs as Sanders, Peyton, Hale 12 having moderate permeability By 90 days of age, four of the five decks would be classified as having moderate permeability The durability factor was determined by AASHTO T161A Most researchers recommend a durability factor of at least 60 to provide adequate freezing and thawing resistance Four of the five bridge decks had durability factors that were greater than 60 Bridge Deck had a durability factor of only 47 which is indicative of poor freezing and thawing resistance Most likely the aggregate source (river gravel) was the cause of the poor durability, since the air contents were near 5% and the specimens experienced cracking near and around the coarse aggregate The final hardened concrete property measured was drying shrinkage Problems with the length change comparator were encountered for the specimens from Bridge Deck The remaining shrinkage values ranged from 339 to 467 microstrains at 112 days of age for specimens casts from Bridge Decks through As with the fresh concrete properties, the hardened concrete properties were ranked and plotted versus the cracking density (Figure 2) to determine if there were any relationships between the hardened properties and cracking for the decks in this study Each hardened property was ranked from to and the rankings were plotted Like the fresh concrete data, there were few if any correlations between the hardened properties and cracking Bridge Deck did have the greatest and 28 day compressive strength and the most cracking, but Bridge Deck which had the second highest crack density also had the lowest compressive strength at and 28 days of age TABLE Hardened Concrete Properties1 Bridge Deck RCIP2 Durability (Coulombs) Factor Unrestrained Shrinkage3 (microstrains) Amount of Cracking ft/ft2 2807 99 NA 0.315 2551 4019 101 451 0.012 2898 5300 86 447 0.1125 4072 2552 105 467 0.0062 3047 2424 47 339 0.051 2429 Permeabilities, durabilities, and shrinkage are averages of four specimens The upper RCIP value is at 28 days and the lower RCIP value is at 90 days Values are at 112 days Sanders, Peyton, Hale 13 FIGURE Hardened concrete properties and crack density Curing As stated previously, AHTD specifications allow the use of several different materials for concrete curing All the materials used to cure the five decks met the specifications AHTD specifications also require that the bridge deck be covered immediately after finishing and that it remains covered for at least days During these days, the curing materials must be kept wet (except for membrane curing) All bridge decks were moist cured for the days, but there differences among the contractors as to when “immediately after finishing” began The application of final cure ranged from 3.5 hours to 15.5 hours after final placement of the deck Also, there were significant differences among the contractors regarding application of the curing compound Curing compound application ranged from 30 minutes to hours after the deck was tined As with the fresh and hardened properties, the curing times and crack density were plotted in Figure Similar to the fresh and hardened properties, there were no correlations or trends observed for all the decks However, the two bridge decks with the greatest amount of cracking Bridge Decks and had the longest time to final cure and the longest time to the application of the curing compound, respectively Sanders, Peyton, Hale 14 FIGURE Curing regimens and cracking density CONCLUSIONS The research program examined the curing regimens and concrete properties of bridge decks The researchers hoped to develop correlations between bridge deck cracking and the concrete properties and curing regimens Due to the many variables involved, it was difficult to pin point one specific concrete property or curing procedure that increased the likelihood or caused bridge deck cracking One early age concrete property that may have increased cracking is compressive strength The variations in early age compressive strength for Bridge Deck may have led to the cracking observed at midspan of the deck However, in the field, it is difficult to identify one specific thing that caused the cracking The findings for the bridge decks included in this study are summarized below There was not a correlation between the amount of bridge deck cracking and the fresh concrete properties that were measured Bridge Deck 1, which had the highest day and 28 day strength, also had the greatest amount of cracking However, this trend does not hold true for the remaining bridge decks, nor does it hold true at other ages Bridge Deck 1, which had the greatest difference between day and day compressive strength, also had the largest amount of cracking This could possibly suggest that large increases in compressive strength during the early ages of the bridge deck may increase the potential for cracking Sanders, Peyton, Hale 15 Bridge Decks and 3, which had the greatest amount of cracking, had the longest time to final cure and the longest time to the application of the curing compound, respectively REFERENCES Transportation Research Board, NCHRP Synthesis 333: Concrete Bridge Deck Performance, National Research Council, Washington, D.C., 2004, pp 101 ACI Committee 201, “Guide to Durable Concrete (ACI 201.2R-06)”, ACI Manual of Concrete Practice, American Concrete Institute, Detroit, Michigan, 2006, pp 39 Xi, Y., Shing, B., Abu-Hejleh, N., Asiz, A., Suwito, A., Xie, Z., and A Ababneh, “Assessment of the Cracking Problem in Newly Constructed Bridge Decks in Colorado”, Rep No CDOT-DTD-R-2003-3, Final Report, Research Branch, Colorado Department of Transportation, Denver, CO January-February 2000 Wiegrenk, K., Marikunte, S., and S.P Shah, “Shrinkage Cracking of High-Strength Concrete”, ACI Materials Journal, Vol 93, No 5, Sept.-Oct 1996, pp 409-415 Schmitt, T R., and D Darwin, “Effect of Material Properties on Cracking in Bridge Decks”, Journal of Bridge Engineering, Vol 4, No.1, Feb 1999, pp 8-13 Krauss, P.D and E.A Rogalla, NCHRP Report 380: Transverse Cracking in Newly Constructed Bridge Decks, Transportation Research Board, National Research Council, Washington, D.C., 1996, pp 126 Holland, T., “Using Shrinkage Reducing Admixtures”, Practice Periodical on Structural Design and Construction, August 1999, pp 89-91 AASHTO Standard Specifications for Highway Bridges, 17th ed., American Association of State Highway and Transportation Officials, Washington, D.C., 2002 Arkansas State Highway and Transportation Department (AHTD), “Standard Specifications for Highway Construction”, 2003  ... Day 259 0 6680 130 6370 57 50 754 0 3420 51 00 50 70 2770 453 0 50 50 357 0 57 80 58 30 1480 3670 4400 2140 359 0 4190 1940 3830 4710 2 350 3780 4940 2860 4430 55 20 4730 9120 2960 4010 4660 3630 4410 53 30... Specifications Slump (in) Air Content (%) 3 .50 3. 25 2. 75 4 .50 7. 25 2 .50 6. 25 3 .50 5. 00 8. 25 6.00 6.00 3 .50 5. 8 6.3 4.9 3.8 3 .5 2.2 3.2 4.6 5. 0 9.2 8.7 5. 7 4.8 1-4 4-8 Calculated Unit Wt (lb/ft3)... (°F) Application 5: 45 AM1 331 68- 95 57 0 .5- 1 hr 12:20 PM 9: 05 PM2 289 89-83 72 hr 3: 05 AM 3: 15 AM3 400 76- 95 69 hr 12:20 PM 6:00 AM4 117 67-94 53 hr 10: 15 AM 7: 05 AM5 171 71-96 53 2 .5 hr 10:40 AM