Construction and monitoring of sustainable concrete bridge A7957 in Missouri, USA

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1 Southern Cross University 23rd Australasian Conference on the Mechanics of Structures and Materials 2014 Construction and monitoring of sustainable concrete bridge A7957 in Missouri, USA E S. Hernandez Missouri University of Science and Technology A Griffin Missouri University of Science and Technology J J. Myers Missouri University of Science and Technology Publication details Hernandez, ES, Griffin, A, Myers, JJ 2014, 'Construction and monitoring of sustainable concrete bridge A7957 in Missouri, USA', in ST Smith (ed.), 23rd Australasian Conference on the Mechanics of Structures and Materials (ACMSM23), vol. II, Byron Bay, NSW, 9-12 December, Southern Cross University, Lismore, NSW, pp ISBN: epublications@scu is an electronic repository administered by Southern Cross University Library. Its goal is to capture and preserve the intellectual output of Southern Cross University authors and researchers, and to increase visibility and impact through open access to researchers around the world. For further information please contact epubs@scu.edu.au.

2 23rd Australasian Conference on the Mechanics of Structures and Materials (ACMSM23) Byron Bay, Australia, 9-12 December 2014, S.T. Smith (Ed.) CONSTRUCTION AND MONITORING OF SUSTAINABLE CONCRETE BRIDGE A7957 IN MISSOURI, USA E.S. Hernandez Missouri University of Science and Technology, Center for Infrastructure Engineering Studies Department of Civil, Arch., & Environmental Engineering, Rolla, MO 65409, USA. A. Griffin Missouri University of Science and Technology, Center for Infrastructure Engineering Studies Department of Civil, Arch., & Environmental Engineering, Rolla, MO 65409, USA. J.J. Myers* Missouri University of Science and Technology, Center for Infrastructure Engineering Studies Department of Civil, Arch., & Environmental Engineering, Rolla, MO 65409, USA. (Corresponding Author) ABSTRACT Self-consolidating concrete (SCC) is a highly flowable nonsegregating concrete that can be placed without any mechanical consolidation and thus has the potential to significantly reduce costs associated to transportation-related infrastructure. In addition to SCC, innovative materials such as High Volume Fly Ash Concrete (HVFAC) also provide a significant potential to produce more cost effective mixtures for Cast-in-Place (CIP) concrete. Since the 1930 s, fly ash a pozzolanic material has been used as a partial replacement of portland cement in concrete to improve the material s strength and durability, while also limiting the amount of early heat generation. From an environmental perspective, replacing cement with fly ash reduces the concrete s overall carbon footprint and diverts an industrial by-product from the solid waste stream. The objective of this implementation project was to investigate the in-situ performance of SCC and HVFAC by monitoring the serviceability and structural response both short-term and long-term of the members of Bridge A7957, built in Osage county, Missouri. The study described in this paper had three major phases: instrumentation and fabrication of precast prestressed (PC/PS) girders, construction and long-term monitoring of Bridge A7957. The results obtained from this two-year study enabled to set certain specification requirements for future project implementations. KEYWORDS Bridge superstructure, extended service life, bridge monitoring, self-consolidating concrete, high volume fly ash concrete. INTRODUCTION An important aspect of using high strength SCC (HS-SCC) infrastructure is that additional reinforcing or prestressing steel can be employed within a reinforced concrete (RC) or PC/PS concrete member. In the case of transportation infrastructure, this benefit comes with a strength gain that permits to reduce the number of girders (used in the transverse direction) or the number of interior supports of the structure. This, in conjunction with reductions in labor and equipment costs as well as decreased maintenance expenses, lessens the overall project costs. Additionally, the flowable characteristic of SCC results in better consolidation and placement with fewer voids and honeycombing. A more condensed microstructure increases the concrete s durability properties, leading to a longer service life, This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this license, visit

3 and thus a more sustainable structure. Despite this and other advantages that come with using HS-SCC, there are some concerns related to its structural behavior due to the constituent materials and proportions. Myers et al. (2012) reported that the effect of the larger paste content and the smaller coarse aggregate size utilized in the mixture is of particular interest. It is critical to monitor the effects of using HS-SCC in PC/PS girders by examining their response regarding prestress losses, shear capacity, creep, shrinkage, thermal gradients, mechanical property development, and serviceability in full-scale infrastructure under varying loads (Myers and Bloch 2010). HVFAC offers an alternative to typical concrete mixtures, producing more durable and longer lasting structures. Material specifications have usually restricted the amount of fly ash to 25 or 30 percent of portland cement replacement. However, Volz et al. (2012) have demonstrated that higher cement replacement percentages, even up to 75 percent, can produce an enhanced concrete in terms of strength and durability. There are still some limitations and concerns related to the application of HVFAC to full-scale structures that need to be investigated. When the fly ash replacement rate is increased, it generally slows down the setting time and hardening rates of concrete at early ages, especially in presence of cold weather conditions, and when less reactive fly ashes are used. Before the design and construction of Bridge A7957, the Missouri Department of Transportation (MoDOT) has incorporated traditional concrete mixtures in their designs. These concretes are not characterized as flowable concretes like SCC, and typically include less than 25% fly ash replacement of Portland cement. Thus, the combination of SCC, HS-SCC, and HVFAC in Bridge A7957 is expected to have a longer useful service life than its infrastructure counterparts composed of conventional concrete. In order to investigate the previously mentioned concerns and the structural performance both shortterm and long-term of some of the RC and PC/PS members of Bridge A7957, an instrumentation plan was generated and implemented during its construction. This plan included the monitoring of the strain and stress variations as well as temperature changes of some PC/PS girders, CIP RC deck, and bents from casting through service life. This project enabled comparing the behavior of the three different concrete mixtures used to fabricate the PC/PS girders, and secondly between the two different concrete mixtures employed in the bents of Bridge A7957 under the same environmental conditions. BRIDGE DESCRIPTION The construction project of Bridge A7957 was executed by the MoDOT during the summer and fall of This bridge is located along Highway 50 in Osage County, Missouri. Bridge A7957 is a threespan, PC/PS concrete bridge, made continuous via a CIP deck (Figure 1 and 2). Span 1-2 (CC) 55.2 MPa (8 ksi) Safety Barrier Span 2-3 (HS-SCC) 68.9 MPa (10 ksi) Span 3-4 (SCC) 55.2 MPa (8 ksi) 1 Bent 1 Int. Diaphragm Bent Safety Barrier Bent 2 (Class B Concrete) Bent 3 (HVFAC) Figure 1. Bridge A7957 (Plan View) Unit Conversion: 1 ft = m The PC/PS concrete NU53 girders in each span were designed with different concrete mixtures. Girders in the first span are m (100 ft) long and were made of conventional concrete (MoDOT s Class A mixture) with a specified compressive strength of 55.2 MPa (8,000 psi). Girders in the second span measure m (120 ft) and were fabricated with a HS-SCC of 68.9 MPa (10,000 psi). The third span measures m (100 ft) and employed SCC with target compressive strength of 55.2 MPa (8,000 psi). ACMSM

4 Figure 2. Bridge A7957 (Elevation) PC/PS concrete panels, with a specified compressive strength of 41.4 MPa (6,000 psi), extend between the top flanges of the girders in the transverse direction and underneath a CIP RC deck (Figure 3). The CIP deck was cast with a conventional concrete mix (MoDOT modified Class B-2) using a 25 % fly ash replacement of portland cement. The target design strength of this concrete mix was 27.6 MPa (4,000 psi). Two intermediate bents and two abutments support the superstructure (Figure 2). The abutments and intermediate bent 2 were built with a conventional concrete mixture (MoDOT Class B) using a 20% fly ash replacement of portland cement with a design compressive strength of 20.7 MPa (3,000 psi). Intermediate bent 3 was cast using HVFAC with a 50% fly ash replacement of Portland cement designed with a specified compressive strength of 20.7 MPa (3,000 psi). INSTRUMENTATION PROGRAM Figure 3. Bridge A7957 (Cross Section) During the preconstruction stage of Bridge A7957, the structural elements instrumented included: the intermediate bents (Figure 4), two PC/PS NU53 girders per span (Figure 5 and 6), and two PC/PS panels located at mid-span. The two instrumented PC/PS panels were situated in span 2-3, between girder lines 2 and 3, and 3 and 4. The type of sensors employed and details about their installation are described in the following subsections. Intermediate Bents Thermocouples were installed within bents 2 and 3 to collect temperature data and obtain thermal gradients following casting. Figure 4 displays the different bent sections where the thermocouple sensors were located. The ambient temperature was measured to adjust for any difference between both concrete mixtures under similar exposure conditions. Within each bent, one thermocouple was placed at the center line of each column 0.92 m (3 ft) from the bottom edge of the pier cap (Figure 4a and Figure 4c). A second set of thermocouples were installed in the web wall at 2.74 m (9 ft) from the center line of each column (Figure 4 and Figure 4b) in the same horizontal plane. At section C (Figure 4a), located 0.30 m (1 ft) from the south end of the pier cap, one exterior and three interior thermocouples were placed according to the detail shown in Figure 4d. Figure 4e shows a thermocouple sensor set at the top layer of a bent s pier cap. Precast Prestressed Girders A total of 86 vibrating wire strain gauges (VWSG) with built-in thermistors, type EM-5, manufactured by Roctest Inc., were employed to monitor the strain and stress variations as well as temperature changes in the PC/PS girders and RC deck from fabrication through service life. ACMSM

5 A B C Pier Cap Web Wall Bottom of Web Wall A B C a) Elevation b) Section A-A TOP MID BOT c) Section B-B d) Section C-C e) Sensor Set within Pier Cap (Top Layer) Figure 4. Thermocouple Installation Details Before casting, a total of 62 VWSG were installed in all spans within the PC/PS girders of lines 3 and 4. Figure 5 shows the PC/PS girder s cluster locations where the VWSG were placed. Within each girder of span (1-2) and span (3-4), the instrumentation clusters were located at two cross-sections, one at mid-span and the second approximately 0.61 m (2 ft) from the support centerline at bent 2 or 3. For span (2-3), the instrumentation clusters were arranged at three different cross-sections; one at midspan and two others at approximately 0.61 m (2 ft) from each support centerline. Span 1-2 (CC) Span 2-3 (HS-SCC) Span 3-4 (SCC) Bent 1 Bent 2 Bent 3 Bent 4 DAS1 DAS 2 Cluster Location (VWSG) Data Acquisition Box Non-Instrumented Girder Unit Conversion: 1 ft = m Figure 5. Bridge A7957 Instrumentation Layout Figure 6 presents the different layers where the VWSG were situated at mid-span and near support sections, respectively. Figure 6c shows a detail of VWSG installed within mid-span of a PC/PS girder previous to concrete placement. The following notation was used to name the layers: a) TD: Top deck (150mm above the bottom fiber of deck) b) BD: Bottom deck (50 mm above the bottom fiber of deck; mid-span only) c) TF: Top flange (50 mm below its top fiber) d) CGC: Center of gravity of composite beam section e) CGU/CGI: Center of gravity of the non-composite beam section (mid-span only) f) CGS: Center of gravity of prestressed strands g) BF: Bottom Flange (50 mm above the bottom fiber) ACMSM

6 Placed at 114 mm from the Panel's Top Fiber Midheight of PC Panel 4 4 CIP Deck a) Mid-span Section b) Near Support Section c) VWSG Installed at Mid-span Figure 6.VWSG Installation within PC/PS Girders and CIP Deck Precast Prestressed Panels and Cast-in-place Deck Within two selected PC/PS panels, one VWSG was set at their mid-height (Figure 7a and Figure 7b). Figure 7c shows the VWSG installed within the CIP deck (mid-span sections). Twenty two VWSG were placed within the CIP RC deck. Twenty of them were set along the longitudinal direction of the girders (Figure 6 and Figure 7c). The last two VWSG were set along the transverse direction of the bridge between girder lines 2 and 3, and girder lines 3 and 4, separated 114 mm from the top fiber of the panels (Figure 6a). These VWSG were installed right above the VWSG located within the panels shown in Figure 7b. a) PC/PS Panel Detail b) PC/PS Panels (After Erection) c) CIP Deck Detail Figure 7. VWSG Installed within Cast-in-place Deck and Precast Prestressed Panels DATA COLLECTION Three data acquisition systems (DAS) were used for data collection during the fabrication and construction of Bridge A7957. A compact RIO system with a NI9214 High Accuracy Thermocouple module was employed for thermocouple data collection in the bents along with a 90 Watt solar panel (Figure 8a). During the girder s fabrication and erection, the vibrating wire strain gauges were connected to either of two Campbell Scientific CR800s (Figure 8b) with AVW200 and AVW206 VWSG reading modules. a) Compact RIO System and Solar Panel b) CR800 DAS Figure 8. Data Acquisition Systems (DAS) ACMSM

7 Intermediate Bents Construction Temperature data was recorded during each of the four castings of the intermediate bents: (1) bent 3 columns and web wall, (2) bent 2 columns and web wall, (3) bent 3 pier cap, and (4) bent 2 pier cap. After the thermocouples were installed, they were connected to the Compact RIO system. Data was collected for approximately hours from the start of each pour. Figure 9 shows the DAS recording data during the pour of the pier cap at bent 3. Figure 9. Data Collection during Pier Cap Construction (Bent 3) Girders and Precast Prestressed Panels Fabrication Two CR800 DAS were employed at the precast plant to record data from the VWSG. The VWSG were connected to the CR800 prior to casting and temperature and strain readings were collected from the pour until after release of the PC/PS girders. Strain and temperature data were also obtained from the two instrumented PC/PS panels from the time of the pour until after release. Figure 10 shows the data recording process during the fabrication of the PC/PS girders and panels. Girders Erection a) Girder Fabrication b) Panel Fabrication Figure 10. Data Collection at Precast Plant Two instrumented girders, identified as S2-G4 and S3-G4 (span 2, girder 4 and span 3, girder 4, respectively) were monitored during their erection. One of the CR800 DAS was fixed to the top of the girder and the VWSG were connected. With the DAS connected during this process, the strain profile at mid-span could be analyzed and compared between the SCC and HS-SCC mix (S3-G4 and S2-G4, respectively). The VWSG remained fixed for an additional 30 minutes after the girder was situated atop the bents. Representative images of this phase of construction are shown in Figure 11 Figure 11. Data Collection during Girder Erection ACMSM

8 MONITORING RESULTS TO DATE Figure 12 shows temperature profile comparisons at early age for the sensors installed within the south side column and web wall of both bents. A temperature profile comparison is also presented for the readings obtained by the sensor placed at the mid-height of the pier cap of both bents. As expected, the hydration heat generated in the case of HVFAC (bent 3) was lesser than in the case of conventional concrete (bent 2). a) Web Wall (SC Sensor) b) Web Wall (SW Sensor) e c) Pier Cap (MID Sensor) Figure 12. Bent Hydration Profile Comparisons Figure 13 shows the temperature profile comparison obtained at sensor M3 (location CGU/CGI in Figure 6) during the first 24 hours, after concrete placement, in girder 3 of span 1-2 and girder 4 of spans 2-3 and 3-4, respectively. Figure 13. Girders Hydration Profile Comparison (Sensor Located at CGU/CGI) Figure 14 shows a comparison of the compressive strength development for both mixtures used to cast the pier caps of bents 2 and 3. As expected, the HVFAC mixture has developed a greater compressive strength than the conventional concrete employed at the abutments and intermediate bent 2. Currently, maturity studies are being undertaken on the different concrete mixes implemented in Bridge A7957. These results will aid the researchers in analyzing the development of mechanical properties in the mixes such as creep, shrinkage, thermal gradients, time dependent behavior and serviceability. Furthermore, continuous monitoring has been undertaken on Bridge A7957 and will ACMSM

9 Compressive Strength (psi) continue until the end of December The static behavior of the structure will be evaluated during a series of live load tests to provide a basis benchmark of the structures response under live loads. The results obtained by the monitoring stage of the project will be used to calibrate and improve computer models based on finite element analysis, and to evaluate any changes in the structure s response during this initial monitoring phase. 7,000 6,000 5,000 4,000 R² = R² = Figure 14. Compressive Strength Development (Bents Web Wall) PRELIMINARY CONCLUSIONS The first full-scale structure implementation of high-strength self-consolidating concrete (HS-SCC) and high volume fly ash concrete (HVFAC) has been conducted on the structure of Bridge A7957 through the Missouri Department of Transportation (MoDOT). High volume fly ash concrete, a sustainable material, at a 50% replacement level was employed within one of the interior supports of this bridge. Coupled with the use of SCC, Bridge A7957 is expected to have a longer service life than traditional reinforced concrete structures. The instrumentation phase of the project has been conducted effectively. Currently, maturity studies are being executed on the different concrete mixtures utilized in Bridge A7957 to compare the differences among the mechanical properties development including: creep, shrinkage, thermal gradients, time dependent behavior and serviceability in the long term. A series of live load tests will be performed during the next phase of this project to establish a benchmark that will be used to monitor any trend in the structure s response and to help validate design assumptions. ACNOWLEDGEMENTS The authors gratefully acknowledge the financial support provided by the Missouri Department of Transportation (MoDOT) and the National University Transportation Center (NUTC) at Missouri University of Science and Technology. REFERENCES 3,000 2,000 1,000 Unit Conversion: 1,000 psi = MPa Fit Curve (Bent 3) Fit Curve (Bent 2) Elapsed Time (days) Myers, J.J., Bloch, K., (2010) Innovative Concrete Bridging Systems for Pedestrian Bridges: Implementation and Monitoring, CIES Report for City of Rolla, Missouri University of Science and Technology, Rolla, Missouri, December 2010, 294 pp. Myers, J.J., Volz, J.S., Sells, E., Porterfield, K., Looney, T., Tucker, B., Holman, K., (2012) Self- Consolidating Concrete (SCC) for Infrastructure Elements: Report A Shear Characteristics, Final Report A MoDOT TRyy1103, Missouri Department of Transportation, Jefferson City, Missouri, August, 2012, 237 pp. Volz, J.S., Myers, J.J., Richardson, D.N., Arezoumandi, M., Beckemeier, K., Davis, D., Holman, K., Looney, T., Tucker, B., (2012) Design and Evaluation of High-Volume Fly Ash (HVFA) Concrete Mixes: Summary Report, Final Summary Report MoDOT TRyy1110, Missouri Department of Transportation, Jefferson City, Missouri, October, 2012, 40 pp. Bent 3 Bent 2 ACMSM