Keywords: Bridge Instrumentation, High-Strength Concrete, High-Strength Self- Consolidating Concrete, Prestress Loss.

Transcription

1 A COMPARATIVE STUDY BETWEEN THE USE OF HIGH-STRENGTH CONCRETE (HSC) AND HIGH-STRENGTH SELF CONSOLIDATING CONCRETE (HS-SCC) FOR ACCELERATED CONSTRUCTION OF PEDESTRIAN BRIDGES Kurt E. Bloch, Missouri University of Science and Technology, Rolla, MO Wei Zheng, Missouri University of Science and Technology, Rolla, MO John J. Myers, PhD, PE, Missouri University of Science and Technology, Rolla, MO ABSTRACT Over time, improvements have been made to the design and the materials used in bridge construction which have lowered costs, reduced construction time, and increased service life. One such improvement has been the use of high-strength concrete (HSC) in prestressed bridges. By using HSC, large sustainable bridge structures were built with relatively compact sections. Recently, high-strength selfconsolidating concrete (HS-SCC) has been developed as a viable alternative to HSC. This type of concrete is highly flowable and does not require vibration during fabrication. This concrete is beneficial in situations where there is congested steel or a need for rapid construction. While HS-SCC appears to be a viable alternative to HSC in prestress applications, several performance related issues remain. For example, the behavior of prestress loss, shear, creep, shrinkage, thermal gradients, mechanical property development, time dependent behavior, and serviceability under varying loads between HSC and HS-SCC remain an issue for investigation. This paper explains the instrumentation and material testing plan used to differentiate the mechanical and material properties of HSC and HS-SCC in two prestressed precast pedestrian bridges constructed in Rolla, MO. In addition, both mild steel and glass fiber reinforced polymer (GFRP) reinforcement were used in the deck systems. By using embedded vibrating wire strain gages (VWSG) with built in thermistors, the differences between prestress losses, thermal gradients, and time dependent behavior was analyzed within the bridge girders and deck panels. In addition, a comparative analysis between the mechanical properties was completed using standard ASTM tests for compression, elastic modulus, split cylinder, creep, and shrinkage on both materials. This paper reports the results received from fabrication through erection. Future work will report load tests on both bridges to monitor the differences in serviceability between the two materials. Keywords: Bridge Instrumentation, High-Strength Concrete, High-Strength Self- Consolidating Concrete, Prestress Loss.

2 INTRODUCTION Throughout the course of history, advancements have been made to the design and materials used in bridge construction which have lowered costs, reduced construction time, and increased service life. One such improvement has been the use of high-strength concrete (HSC) in prestressed bridges. By using HSC, large sustainable bridge structures were built with relatively compact sections. Recently, high strength self-consolidating concrete (HS- SCC) has been developed as a viable alternative to HSC. With the added improvement of being highly flowable and not requiring vibration during fabrication, HS-SCC can be very beneficial in situations where there is congested steel or a need for rapid construction 1. Combining with precasting prefabricated bridge sections, construction time can be greatly reduced 2. Before HS-SCC can be used as a viable alternative to HSC, performance related issues require close inspection. For example, the behavior of prestress loss, shear, creep, shrinkage, thermal gradients, mechanical property development, time dependent behavior, and serviceability under varying loads between HSC and HS-SCC remain an issue for investigation 1. Within this investigation, concrete temperature, concrete strain, beam camber and deflection are monitored to determine the differences between the thermal gradients, prestress losses, beam curvatures, and time dependent behavior of HSC and HS-SCC girders. In addition, mild steel and glass fiber reinforced polymer (GFRP) were used within the deck panels to see how this affected concrete temperature, concrete strain, and deflection within the bridge deck systems per concrete type. These goals are achieved by using embedded vibrating wire strain gauges with built in thermistors, surface mechanical strain gauges (DEMEC), tensioned wire deflection measuring system, and precise surveying to determine the differences in HSC and HS-SCC in early-age and later-age monitoring. In addition, material specimens were fabricated and tested using standard ASTM testing procedures to determine and compare the mechanical properties of the two concrete materials. Tests that were completed were compression, elastic modulus, modulus of rupture, split cylinder, creep, and shrinkage on both materials. This paper will exhibit the instrumentation and testing program to determine the properties of the various concretes, and it will show early-age test results from the instrumentation and testing procedures 3. INTRODUCTION OF BRIDGES Two precast pedestrian bridges were erected along Lions Club Drive in Rolla, MO consisting of HSC and HS-SCC. The single span HSC pedestrian bridge is located near Highway O and spans a length of 14.6m (48-ft) and has a width of 3.0m (10-ft). The HS-SCC single span bridge located near Rolla Street spans a length of 10.7m (34-ft) and has a width of 3.0m (10- ft). The bridge implemented prestressed L girders to function as the structural support of the bridge and the handrails for the pedestrians. Within the girders, twelve 12.7mm (0.5-in) diameter pretensioned strands were used to reinforce the single span concrete bridges. Both bridges have two spandrels to form the bridge deck. One spandrel was reinforced with mild steel. The other spandrel was reinforced with GFRP. Both the spandrels and the beams were fabricated at a precasting plant in Marshall, MO. By only needing two girders and two 2

3 spandrels, two bridges were rapidly transported and erected in a single day provided that the abutments were fabricated in advance. Along with the benefit of rapid construction, the addition of decorative beams and sandblasting allowed each bridge to have a splendid aesthetic appeal. The cross section of the bridge is illustrated in Figure 1. In addition, Figure 2 displays the girder cross section and prestressed strand arrangement. In addition, images of the final bridges are presented in Figure 3. Each bridge had a target compressive strength of 68.9MPa (10,000 psi) and a release strength of 24.1MPa (3,500 psi). However, due to the rapid strength gain of the concrete, the actual release strength was much higher than required. The HSC bridge had a 28 day compressive strength of 84.7MPa (12,280 psi) and a release strength of 46.6MPa (6,770 psi). The HS- SCC bridge had a 28 day compressive strength of 72.4MPa (10,500 psi) and a release strength of 44.8MPa (6,500 psi) JT FLAT SLAB WIDTH 13 JT. OF WALK BRIDGE 140 RP001G 10 X 203 X 203 W/(4) Ф 13 X 152 H.A.S RP001G RP001G 10 X 203 X 203 W/(4) Ф 13 X 152 H.A.S. 203 RP001G 6 76 RE005G 102 X 13 X 102 CENTERED ON RP001G Units: mm (1 mm = in ) Fig. 1 Cross-Section of HSC and HS-SCC Bridges 3

4 (6) 12.7 mm (0.5 in) diameter 66.7 kn (15 kips) (6) 12.7 mm (0.5 in) diameter kn (31 kips) Units: mm (1 mm = in ) Fig. 2 Cross Section of HSC and HS-SCC Bridge Girders a.) HSC Bridge Located Near Hwy O b.) HS-SCC Bridge Located Near Rolla St. Fig. 3 Picture of HSC and HS-SCC Bridge along Lions Club Drive in Rolla, MO Table 1 and Table 2 detail the mix designs used for each bridge in order to produce the necessary strength levels. It should be noted that the water to cement ratio for the HSC mix is slightly lower than that of the HS-SCC mix. In addition, the HSC mix contains a higher amount of coarse aggregate than the HS-SCC mix. 4

5 Table 1 HSC Mix Design TYPE MATERIAL WEIGHT Cementitious Materials Coarse Aggregate Fine Aggregate Admixtures Ashgrove Gray Type III 340 kg/m 3 (750 lbs/yd 3 ) Microsilica 26 kg/m 3 (58 lbs/yd 3 ) 12.7 mm (1/2 ) Canyon Gray Granite 769 kg/m 3 (1695 lbs/yd 3 ) Kaw River Sand 560 kg/m 3 (1235 lbs/yd 3 ) 3.56 L (0.94 gal)high Range Water Reducer 1.81 kg/m 3 (4 lbs/yd 3 ) 0.95 L (0.25 gal) Retarder Water 117 kg/m 3 (259 lbs/yd 3 ) w/cm Table 2 HS-SCC Mix Design TYPE MATERIAL WEIGHT Cementitious Materials Ashgrove Gray Type III 299 kg/m 3 (660 lbs/yd 3 ) Thomas Hill Type C Fly Ash 54 kg/m 3 (120 lbs/yd 3 ) Coarse Aggregate Grade E Cedar Valley Limestone 465 kg/m 3 (1025 lbs/yd 3 ) Kaw River Sand 612 kg/m 3 (1350 lbs/yd 3 ) Fine Aggregate 9.5 mm (3/8 ) Cedar Valley Limestone Chips 212 kg/m 3 (467 lbs/yd 3 ) Admixtures 1.02 L (0.27 gal) Air Entrainment 3.03 L (0.8 gal) High Range 4.08 kg/m 3 (9 lbs/yd 3 ) Water Reducer (HRWR) Water 115 kg/m 3 (254 lbs/yd 3 ) w/cm

6 INSTRUMENTATION PLAN An instrumentation system was designed and fabricated for both the HSC and HS-SCC bridges to monitor both the girders and spandrels during early-age and later-ages. The primary goals of the instrumentation program were as follows: 1. Monitor immediate and long-term prestress losses; 2. Monitor deflections from transfer through service life; 3. Compare the measured deflections with predicted deflections; 4. Monitor stresses along the spans at the center of gravity of the steel due to prestressing, applied loads, and thermal effects; 5. Develop stress/strain blocks along the depth of the members at both the near-end supports and mid-span; 6. Monitor thermal gradients at similar cross sections; 7. Evaluate distribution of loading with a live load test after the construction has been completed; 8. Monitor transfer length for prestressing strands in the actual beams used in the structure; 9. Examine the properties of normal HSC compared to HS-SCC 10. Compare the performance of precast deck panels with varying reinforcements. To achieve the above objectives, 16 vibrating wire strain gauges (VWSG) with embedded thermistors were installed in the precast girders and deck. A data acquisition system (DAS) with ample channels was designed and programmed for the project. Figures 4 and 5 illustrate where the cluster locations of instrumentation were embedded at the support and mid-span of the girders and the mid-span of the spandrels in both the HSC and HS-SCC bridges. Within the spandrels, the VWSG were oriented in two directions. The top and bottom sensors were oriented in the lateral direction of the bridge to measure the flexural strains. The middle sensor was oriented in the longitudinal direction of the bridge to measure the strains caused by temperature and shrinkage. The VWSG were used to determine the strain and temperature profile within the girder and bridge deck. The sensors have proven to be reliable in past research projects 3. Currently, all of the sensors have functioned adequately on the bridge systems. The locations of the sensors within the girders and spandrels are displayed in Figure 6 and Figure 7 respectively. Each span is denoted with an A or a B. The A represents the panels which were reinforced with mild reinforced steel. The span denoted with a B represents the panels which were reinforced with GFRP. To determine and study the transfer length, DEMEC strain gauge points have been utilized. For early-age conditions, a tension wire system was used to determine the early-age serviceability of the bridge members. For later-age serviceability results, precise surveying equipment (i.e. laser based) will be used to monitor bridge deflections. 6

7 Span A Cluster Locations Girder Spandrels Span B Data Acquisition System Units: mm (1 mm = in ) Fig. 4 Illustration of Instrumentation Plan Showing Cluster Locations (Plan View) for HSC Bridge Span B Cluster Locations Girder Spandrels Span A Data Acquisition System Units: mm (1 mm = in ) Fig. 5 Illustration of Instrumentation Plan Showing Cluster Locations (Plan View) for HS-SCC Bridge 7

8 Vibrating Wire Strain Gage (VWSG) Units: mm (1 mm = in ) a.) Girder Cross Section During Fabrication b.) VWSG in Girders at Support during Fabrication in Marshall, MO c.) VWSG in Girders at Mid-Span during Fabrication in Marshall, MO Fig. 6 Location of Sensors along Cross Section of Girders 8

9 Vibrating Wire Strain Gage (VWSG) Units: mm (1 mm = in ) a.) Deck Panel Cross Section During Fabrication b.) VWSG in Middle of Precast Deck Panels with Mild Steel Reinforcement c.) VWSG in Middle of Precast Deck Panels with GFRP Reinforcement Fig. 7 Location of Sensors within Cross Section of Spandrels (Note Middle Sensor Measures Temperature and Shrinkage Strain) MATERIAL TESTING In addition to the instrumentation system, a material testing program was implemented to test the compressive strength, tensile strength, modulus of elasticity, modulus of rupture, creep, and shrinkage of HSC and HS-SCC in both the beam and girders using standard ASTM testing procedures. All but the creep and shrinkage test specimens were allowed to cure in an environment similar to field conditions. The creep and shrinkage specimens have been kept inside a laboratory maintained at room temperature. A summary of the testing program is presented in Table 3. 9

10 Table 3 Material Testing Program TESTS TEST METHOD SPECIMENS DATES OF TEST Compressive Strength Modulus of Elasticity Splitting Tensile Strength ASTM C 39 ASTM C469 ASTM C mm dia. x 203.2mm long cylinder (4-in. dia. x 8-in. long cylinder) Modulus of Rupture ASTM C mm x 152.4mm x 533.4mm (6-in. x 6-in. x 21-in.) and 152.4mm x 152.4mm x mm (6-in x 6-in x 24-in) Creep ASTM C mm dia. x 609.6mm long cylinder Shrinkage ASTM C 490 (4-in. dia. x 24-in. long cylinder) Release, 4 days, 7 days, 14 days, bridge erection, 28 days, 1 year, 2 year Release, 4 days, 7 days, 28 days, bridge erection, 1 year, 2 year Release, 7 days, 28 days, 1 year After bridge erection After girder and spandrel pour FABRICATION Both the girders and the deck panels were fabricated at a precasting plant in Marshall, MO. Before the beams and deck panels were poured, the VWSG were installed into the predetermined locations within the members and connected to the DAS by the research team. During the pour, material test specimens were fabricated from each mix. After the girders were allowed to cure for twenty hours, DEMEC points were attached to the members and a base line reading was determined. Soon after taking the base reading, the beams were released and a second reading was made of the DEMEC points to determine the elastic losses in the prestressed concrete. After the girders were allowed to cure, the beams were sandblasted for the desired aesthetic finish. Both the beams and spandrels were shipped to Rolla, MO. During the transfer, the DAS was connected to the sensors in both girders to monitor the effects of transfer on the prestressed members. Both bridges were erected in a single day. Both of the girders and the panels were set into place with a large crane. Before the spandrels were placed, the girders were welded to the abutments and neoprene pads were set on the girders at support points for the spandrels. Soon after, the spandrels were welded to the girders. Table 4 presents a timeline of the fabrication and erection of the bridges. In addition, Figure 8 and Figure 9 show images of the fabrication and erection of the bridges respectively. 10

11 Table 4 Timeline of Bridge Fabrication and Testing ACTIVITY Install Instrumentation Fabrication Sand Blasting Erection Load Test 1 Load Test 2 Load Test 3 HSC GIRDER 7/29/ :00 7/30/ :00 8/3/ :00 9/30/2009 9:45 HS-SCC 7/29/2009 7/30/2009 8/3/2009 9/30/2009 GIRDER 16:00 11:00 10:00 15:15 9/30/2009 HSC 8/20/2009 8/21/2009 NA 11:35 & PANELS 15:00 11:00 11:50 9/30/2009 HS-SCC 8/20/2009 8/21/2009 NA 16:25 & PANELS 17:00 10:30 16:38 Notes: Start Time denoted in hr:min below activity date. 3/ / /2011 3/ / /2011 3/ / /2011 3/ / /2011 a.) HSC Girder Fabrication b.) HS-SCC Deck Panel Fabrication Fig. 8 Bridge Girder and Spandrel Fabrication at Coreslab Structures, Inc. in Marshall, MO 11

12 a.) Crane Lifting HS-SCC Bridge Girder b.) HS-SCC Bridge Girder Being Set during Bridge Erection Fig. 9 Bridge Erection in Rolla, MO MECHANICAL RESULTS EARLY-AGE PRESTRESS LOSSES After allowing the beams to cure for 20 hours, DEMEC points were applied to the bridge girder and a preliminary reading was taken. After the readings had been taken, the prestress tendons were cut. After the tendons were cut, the bridge girders were lifted and taken outside to continue curing. During this time period, a second reading was taken on the DEMEC points to determine the immediate elastic shortening losses. They were determined to be 17.3MPa (2,0 psi) for the HSC girder and 14.7MPa (2,130 psi) for the HS-SCC girder. Therefore, the elastic shortening loss was 1.6% for the HSC girder and 1.4% for the HS-SCC girder effectively at release. TEMPERATURE PRIOR TO RELEASE Between each prestressing strand in the concrete, a VWSG was placed with an embedded thermistor to record the internal temperature and strain during the casting of the girders. In addition, the sensors will continue recording data during the remainder of the research program. Figures 10 and 11 report the early-age temperature within the supports of the HSC and HS-SCC girders prior to release. 12

13 7/30/2009 7/30/2009 7/30/2009 Time 7/31/2009 7/31/2009 7/31/ Temperature ( C) Temperature ( F) CB-M1 CB-M2 CB-M3 CB-M4 CB-M Units: mm (1 mm = in) Hours After Placement Fig. 10 Early Age Internal Concrete Temperature in HSC Beam at Mid-span 7/30/2009 7/30/2009 7/30/2009 Time 7/31/2009 7/31/2009 7/31/ Temperature ( C) Temperature ( F) SB-M1 SB-M2 SB-M3 SB-M4 SB-M Units: mm (1 mm = in) Hours After Placement Fig. 11 Early Age Internal Concrete Temperature in HS-SCC Beam at Mid-span 13

14 From the data shown, it can be inferred that areas closest to the edge of the form or exterior of the beam dissipated the most heat. The temperature was not highly varied due to the way the concrete was placed and the member orientation on the bed. Due to the beam orientation on the prestressing bed, the concrete dissipated heat in a uniform fashion. Only the edges closest to the forms did not accumulate as much heat as in the middle. Similar dissipation of heat can be seen in investigations of I-shaped sections 4. The peak temperature of the HSC was in the center of the beam and reached a temperature of 61.6 C (142.8 F). The peak temperature of the HS-SCC was also in the center of the beam and reached a temperature of 58.0 C (136.4 C). It can be observed within this investigation that the hydration temperature was slightly higher for the HSC mix than for the HS-SCC mix. By examining the mix design, the HSC mix contained 21.6% Portland cement while the HS-SCC mix contained 21.5% cement. This slight increase in cement in the mix design could contribute to the differences in peak hydration temperature 5. MATERIAL PROPERTY RESULTS COMPRESSIVE STRENGTH The targeted compressive strength of the bridge was 68.9MPa (10,000 psi) at erection and the release strength was 24.1MPa (3,500 psi). To monitor the compressive strength and compare the HSC to HS-SCC, compressive test cylinders were cured in field conditions and tested at the dates specified earlier. Figure 12 illustrates the strength gain between the HSC and HS- SCC mixes for the deck panels Compressive Strength (MPa) MPa (3,500 psi) Release Strength Age of Mix (Days) HSC HS-SCC Fig. 12 Compressive Strength of HSC and HS-SCC versus Age of Concrete 14

15 MODULUS OF ELASTICITY (MOE) RESULTS Modulus of elasticity (MOE) tests were undertaken at the same time as the compression tests. The modulus of elasticity test results of each mix is displayed in Table 5. By examining the results, a few observations can be made. The elastic modulus of HS-SCC was slightly higher than the elastic modulus of HSC for the 7/30/2009 casting date. However, the 8/21/2009 casting date HSC exhibited a slightly higher modulus of elasticity compared to the HS-SCC mix. The HSC mix contained higher amounts of stiffer granite coarse aggregate compared to the HS-SCC mix which contained limestone aggregate. It was expected that the HS-SCC would have a slightly lower modulus of elasticity because it contained less coarse aggregate which has a major effect on MOE. However, only the 8/21/2009 mix behaved as expected. Both of the mix designs, however, produced lower than anticipated MOE when compared to the ACI empirical relationship. However, when compared to the empirical relationship for HSC as cited in ACI as Eq. 6-5 which takes into account type of cementitious material and aggregate type, the results are fairly reasonable for the HSC mix. However, all of the empirical relationships over predict the MOE for the HS-SCC mix. This suggests that special attention is likely required for long-span or serviceability controlled designs using similar mix designs as the HS-SCC used in this study. More research is required to better understand the mechanical properties of HS-SCC such as MOE. Equations 1 and 2 present the ACI method for estimating MOE and an empirical model cited in ACI (psi) ACI (1) (psi) ACI (2) In the equations above, w c is the unit weight of the concrete in pounds per cubic foot, f c is the 28 day compressive strength in pounds per square inch, and k 1 and k 2 are constants dependent upon the cementitious materials and aggregate used in the mix. For the mixes in this project, both of the material k 1 values were equal to 1.0 for HSC and 1.2 for HS-SCC due to the aggregate type. In addition, the k 2 values varied between 0.95 for the HSC due to the slag in the mix and1.10 for the HS-SCC because the mix contained fly ash. Table 5 28 Day Modulus of Elasticity for HSC and HS-SCC Mix Casting Date Modulus of Elasticity 7/30/2009 (girder) 28,300 MPa 4,100 ksi HSC 8/21/2009 (spandrel) 33,800 MPa 4,900 ksi ACI empirical 44,100 MPa 6,390 ksi ACI empirical 33,400 MPa 4,840 ksi 7/30/2009 (girder) 32,100 MPa 4,650 ksi HS-SCC 8/21/2009 (spandrel) 33,100 MPa 4,800 ksi ACI empirical 38,600 MPa 5,600 ksi ACI empirical 41,000 MPa 5,950 ksi 15

16 SHRINKAGE RESULTS Shrinkage and Creep cylinders were stripped after 24 hours and DEMEC points were applied to monitor shrinkage. Figure 13 illustrates the results from the shrinkage tests over the first 181 days Strain (microstrain) HSC Shrinkage HS-SCC Shrinkage Age of Mix (Days) Fig. 13 Shrinkage Results for HSC and HS-SCC Bridge Panels Based upon the mix design, if all mix constituent material and contents were similar, one would expect the HS-SCC mix to have a very slight higher level of shrinkage because of its slightly higher water to cement (w/cm) ratio of when compared to HSC w/cm ratio of However, this is not consistent with the data obtained. In a previous study, researchers have reported that concrete containing limestone displayed less shrinkage when compared to a stiffer aggregate, such as gravel, due to a possible chemical reaction between the paste and the limestone creating a stronger bond at the interface zone 8. In the bridge mix designs, the HS-SCC mix consisted of coarse aggregate of limestone and the HSC consisted of a coarse aggregate of granite. The type of aggregate could play a more significant roll on shrinkage due to the w/cm ratio being relatively close. The shrinkage graphs do not exhibit a smooth curve due to slight variations in the structural engineering laboratory ambient environment. While the laboratory are generally consistent, on some days humidity levels and temperature vary somewhat on particular days as loading dock doors are opened and closed for large scale specimen delivery and removal. This could contribute to the bumps exhibited in the figure 5. 16

17 CREEP RESULTS Within 24 hours of the bridge being erected on September 30, 2009, two creep cylinders of each material were loaded at 20% and 40% respectively of the targeted 28-day compressive strength. The values obtained from taking readings from the specimens in the load frames include both shrinkage and creep data. In order to obtain only the creep deformation, the shrinkage data obtained from the shrinkage specimens was subtracted from the total deformation of the specimens in the load frame. In addition, the elastic deformation was removed from the first day data. The remaining data is the amount of creep caused by the applied sustained load. Figure 14 displays the creep results for the girder mixes HSC Loaded 20% HSC Loaded 40% HS-SCC Loaded 20% HS-SCC Loaded 40% Strain (Microstrain) Days After Loading Fig. 14 Creep Results for HSC and HS-SCC for Bridge Girders As illustrated in Fig. 14, the amount of creep is greater for the HS-SCC compared to the creep for the HSC. The creep of the HSC is less than the HS-SCC due to the aggregate type and amount of coarse aggregate. The HSC utilizes a granite coarse aggregate which has a fairly high stiffness when compared to the limestone used in the HS-SCC mix. In addition, the HSC has a higher amount of coarse aggregate than the HSC. All of these factors can lessen the degree of creep within a mix 9. 17

18 SUMMARY Within this report, an instrumentation and material test plan have been shown and undertaken for an HSC and HS-SCC pedestrian bridge project in Rolla, MO. Currently, the following tasks have been completed and observations have been made: 1. Instrumentation system has been developed and utilized to monitor the temperature and strain within both HSC and HS-SCC bridge girders and spandrels to determine the differences in thermal gradients and prestress losses between the two types of concretes. 2. A material testing program has been developed and implemented to test compressive strength, modulus of elasticity, split tension, modulus of rupture, creep, and shrinkage and compare the material properties of HSC and HS-SCC. 3. The bridges have been successfully installed in Rolla, MO, with the instrumentation system functioning adequately. 4. The stresses lost due to elastic shortening were determined to be 17.3MPa (20 psi) for the HSC girder and 14.7MPa (2130 psi) for the HS-SCC girder. Therefore, the elastic shortening loss was 1.6% for the HSC girder and 1.4% for the HS-SCC girder. 5. The peak hydration temperature of the HSC was in the center of the beam and reached a temperature of 61.6 C (142.8 F). The peak temperature of the HS-SCC was also in the center of the beam and reached a temperature of 58.0 C (136.4 C). 6. The compressive strength of the HSC was found to be 84.7MPa (12,280 psi) and the HS- SCC was found to be 72.4MPa (10,500 psi). 7. The shrinkage of the concrete observed was greater in the HSC compared to that of the HS-SCC. 8. The creep of the concrete was greater for the HS-SCC than the HSC. 9. The modulus of elasticity observed was lower than predicted by current empirical models. HSC MOE models did not accurately predict the MOE for the HS-SCC elements. The following tasks are in process and on-going: 1. The instrumentation system will continue monitoring temperature and strain within both the HSC and HS-SCC bridge girders and spandrels during bridge operation to determine long term differences in thermal gradients and prestress losses between the two types of concrete. 2. Later age material tests are to be completed to determine the later age compressive strength, modulus of elasticity, split tension, modulus of rupture, creep, and shrinkage and compare the material properties of HSC and HS-SCC. 3. A load test is to be completed this year and two more in the future to monitor differences in deflection and serviceability between the material types. 18

19 ACKNOWLEDGEMENTS The authors of the paper would like to thank the City of Rolla, Missouri, Coreslab Structures, Inc. in Marshall, MO, and Hughes Brothers of Seward, Nebraska, for their support in this research project. In addition, the authors would like to thank the National University Transportation Center and the Center for Infrastructure Engineering Studies at Missouri S&T for their involvement in the project. REFERENCES 1. Khayat, Kamal H., Mitchell, Denis, Self-Consolidating Concrete for Precast, Prestressed Concrete Bridge Elements, National Cooperative Highway Research Program Report 628, Shahawy, Moshen A. Prefabricated Bridge Elements and Systems to Limit Traffic Disruption During Construction, National Cooperative Highway Research Program Synthesis 324, Myers, J.J., Yang, Y. Field and Laboratory Performance of Prestressed High Performance Concrete Girders for Missouri Bridge Structures, Center for Infrastructure Engineering Studies, Report Number 04-49, University of Missouri-Rolla, Rolla, Missouri, June Yang, Y., Shen, J., Myers, J.J., Instrumentation and Early-Age Monitoring of High Performance Concrete Bridge Girders in Missouri, Transportation Research Board 81 st Annual Meeting, Washington, D.C., MacGregor, James G., Wight, James K., Reinforced Concrete Mechanics and Design Fourth Edition, Upper Saddle River, New Jersey, American Concrete Institute (ACI ) (2008), Building Code Requirements for Structural Concrete, American Concrete Institute, Detroit, Michigan. 7. American Concrete Institute (ACI ) (2010), Report on High Strength Concrete, American Concrete Institute, Detroit, Michigan. 8. Al-Attar, Tareq Salih, Effect of Coarse Aggregate Characteristics on Drying Shrinkage of Concrete, Eng&Tech. Vol.26, No. 2, Nawy, Edward G., Prestressed Concrete: A Fundamental Approach Fifth Edition, Upper Saddle River, New Jersey,