EVALUATION OF DURABILITY OF ODOT PRESTRESSED/PRECAST CONCRETE IN OHIO

Transcription

1 EVALUATION OF DURABILITY OF ODOT PRESTRESSED/PRECAST CONCRETE IN OHIO BY NICK SCAGLIONE, PRESIDENT CONCRETE RESEARCH & TESTING, LLC 400 FRANK ROAD COLUMBUS, OHIO SEPTEMBER 2002 PREPARED FOR THE OHIO DEPARTMENT OF TRANSPORTATION

2 1. Report No. 2. Government Accession No. 3. Recipient's Catalog No. FHWA/OH-2002/ Title and Subtitle Evaluation of Durability of Prestressed/Precast Concrete in Ohio 5. Report Date September Performing Organization Code 7. Author(s) Mr. Nick Scaglione 8. Performing Organization Report No. 10. Work Unit No. (TRAIS) 9. Performing organization Name and Address Concrete Research & Testing, LLC 400 Frank Road Columbus, Ohio Sponsoring Agency name and Address Ohio Department of Transportation 1980 W Broad Street Columbus, OH Supplemental Notes 11. Contract or Grant No. State Job No (0) 13. Type of Report and Period Covered Final Report 14. Sponsoring Agency 16. Abstract The Ohio department of Transportation (ODOT) wanted to determine the permeability of prestressed/precast concrete supplied to them for bridge components. Permeability testing was performed using the rapid chloride permeability test method (ASTM c 1202) on concrete cores removed from precast test sections that were prepared at each of ODOT s prestressed/precast suppliers. The test sections were cast and cured along with production bridge components. The results of this testing were compared with previous rapid chloride permeability results from ODOT high performance concrete bridge projects. ODOT s high performance concrete used for cast-in-place bridge decks contains supplementary cementitious materials (fly ash, GGBF Slag, micro-silica), while the prestressed/precast concrete supplied to ODOT contains only Type III Portland cement such as the cementitious components. The precast concrete typically has a reduced watercementitious ratio compared to the cast-in-place concrete. Some of the prestressed/precast manufacturers produced concrete which obtained very low permeability values at 90 days (<1000 Coulombs). However, the permeability results of the prestressed/precast concrete varied widely between individual manufacturers. The results of the permeability testing showed that the prestressed/precast concrete has a higher permeability compared to ODOT s high performance cast-in-place concrete. The effect of heat testing on the permeability of the prestressed/precast concrete was also examined. For the conditions of the present study, the specimens that were heat cured has similar permeability values compared to companion specimens that were not heat cured. Compressive strength testing was performed as part of the study to determine if the strengths that the prestressed/precast manufacturers measure on test cylinders for release strengths are representative of the cast-in-place concrete strength. The test results from this study showed that the strength of the concrete test cylinders correlated well with concrete cores taken from the precast test section. 17. Key Words 18. Distribution Statement permeability; prestressed/precast concrete; No Restrictions. This document is box beam; rapid chloride permeability test; available to the public through the supplementary cementitious materials; heat cure National Technical Information Service, Springfield, Virginia Security Classif. (of this report) 20. Security Classif. (of this page) 21. No of Pages 22. Price Unclassified Unclassified FORM DOT F (8-72) Reproduction of complete page authorized

3 EVALUATION OF DURABILITY OF ODOT PRESTRESSED/PRECAST CONCRETE IN OHIO BY NICK SCAGLIONE, PRESIDENT CONCRETE RESEARCH & TESTING, LLC 400 FRANK ROAD COLUMBUS, OHIO SEPTEMBER 2002 PREPARED FOR THE OHIO DEPARTMENT OF TRANSPORTATION Prepared in cooperation with the Ohio Department of Transportation and the U. S. Department of Transportation, Federal Highway Administration. The contents of this report reflect the views of the author who is responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Ohio Department of Transportation or the Federal Highway Administration. This report does not constitute a standard, specification or regulation.

4 TABLE OF CONTENTS I. Introduction 1 A. Permeability Test Method 2 II. Background 2 III. Objectives 4 IV. Work Plan 5 A. Concrete Mix Designs 5 B. Preparation of Test Specimens 6 C. Curing and Coring of Test Specimens 7 D. Testing of Specimens 9 1. Compressive Strength Testing 9 2. Rapid Chloride Permeability Testing 9 V. Results of Testing 10 A. Compressive Strength Testing 10 B. Rapid Chloride Permeability Testing Effect of Heat Curing Comparison of Precast Concrete to ODOT High Performance Cast-in-Place Concrete 12 VI. Conclusions 14 VII. Recommendations 14 VIII. References 15 IX. Appendix A: Tables and Charts A-1 X. Appendix B: Photographs B-1 i

5 LIST OF TABLES Table No. Table Title Page No. Table A1 List of ODOT pre-qualified manufacturers of prestressed/precast box beams. A-1 Table A2 Ohio Department of Transportation High Performance Concrete Mix Designs (from Supplemental Specification 844). A-2 Table A3 Concrete Mix Designs used for each of the prestressed/precast manufacturers. A-3 Table A4 Mixer type, method of transporting and placing concrete and vibration methods used for each of the prestressed/precast manufacturers. A-4 Table A5 Fresh concrete properties measured on each of the test mixes. A-5 Table A6 Summary of Curing Information for Each of the Prestressed/Precast Manufacturers. A-6 Table A7 Compressive Strength Test Results of Concrete Cores. A-8 Table A8 Compressive Strength Test Results of Concrete Cylinders. A-9 Table A9 Rapid Chloride Permeability Test Results of Concrete Cores. A-11 Table A10 Rapid Chloride Permeability Test Results of Concrete Cylinders A-12 ii

6 LIST OF FIGURES Figure No. Figure Title Page No. Figure A1 Typical Temperature Curves of Precast Concrete Test Sections. A-7 Figure A2 Compressive Strength Test Results of Concrete Cores and Cylinders. A-10 Figure A3 Rapid Chloride Permeability Test Results of Concrete Cores and Cylinders. A-13 Figure A4 Rapid Chloride Permeability Test Results of Concrete Cores and Cylinders. A-14 Figure A5 Rapid Chloride Permeability Test Results of Concrete Cores and Cylinders. A-15 Figure A6 Rapid Chloride Permeability Test Results of Concrete Cores and Cylinders. A-16 Figure B1 Molds set up for the casting of box beam test sections. B-1 Figure B2 Molds set up for the casting of box beam test sections. B-2 Figure B3 Casting of box beam test sections. B-3 Figure B4 Casting of box beam test sections. Temperature monitoring of test sections. B-4 Figure B5 Sampling of concrete for testing and the casting of test cylinders. Casting of concrete test cylinders. B-5 Figure B6 Curing of the box beams. B-6 iii

7 LIST OF FIGURES Figure No. Figure Title Page No. Figure B7 Removal of the test sections from the molds the morning after casting. B-7 Figure B8 Coring of box beam test sections. B-8 Figure B9 Compressive Strength Testing of Concrete Core at Precast Plant. Rapid Chloride Permeability Testing at CRT. B-9 iv

8 INTRODUCTION Currently the Ohio Department of Transportation (ODOT) has prestressed/precast concrete box beam bridges in service that exhibit spalling due to corrosion of the prestressed strand (as reported by ODOT personnel). The primary protection for the strand is concrete cover. The American Association of State Highway and Transportation Officials (AASHTO) allows prestressed/precast concrete to have a reduced concrete cover over the reinforcing steel compared to cast-in-place concrete. 1 The American Concrete Institute (ACI) has a similar specification. 2 The lower cover thicknesses for prestressed/precast concrete is allowed due to the general perception that prestressed/precast concrete is more durable than cast-in-place concrete. 2,3 A substantial amount of Rapid Chloride Permeability Testing (ASTM C 1202 test method) has been performed on ODOT high performance cast-in-place concrete used for bridge decks. However, there has been virtually no permeability testing on the prestressed/precast concrete supplied to ODOT for use in bridge construction. ODOT is interested in determining the general permeability characteristics of the concrete used for prestressed/precast bridge components. In particular they are interested in how the permeability of the prestressed/precast concrete compares to the ODOT high performance cast-in-place concrete used for bridge decks. Currently there are eight pre-qualified prestressed/precast manufacturers who can supply box beams to ODOT. The eight manufacturers are listed in Appendix A - Table A1. The testing program described in this report was conducted for each of the eight manufacturers.

9 Permeability Test Method The concrete was tested using the Rapid Chloride Permeability Test (RCPT). This test method is described in ASTM C Standard Test Method for Electrical Indication of Concrete's Ability to Resist Chloride Ion Penetration. This test is not a true measure of concrete permeability. The test measures the electrical conductance of the concrete, which can be correlated to concrete permeability. The test consists of monitoring the amount of electrical current passed through a 50 mm thick x 100 mm diameter (2 in. x 4 in.) saturated concrete specimen during a 6 hour period. A potential difference of 60 volts is maintained across the ends of the specimen. The test measures the total charge passed, in coulombs, during the 6 hour test period. A concrete with a high permeability will allow a high amount of current to pass through the concrete and therefore have a high coulomb value. A concrete with a low permeability will result in a low amount of current passing through the concrete and therefore have a low coulomb value. Concrete having a total charge passed of less than 1000 coulombs is considered to have a very low permeability. BACKGROUND Producing concrete in a precast environment can have many advantages over cast-in-place concrete. It is possible to place the concrete under more controlled conditions and therefore a more consistent product can be produced. The precast situation typically allows the concrete to be placed very shortly after the mixing operation. Improved vibration is also possible for precast concrete. Due to these factors it is possible to produce concrete at reduced water-cement ratios compared to cast-inplace concrete. More efficient concrete mixers can also be used which have the potential to produce concrete with reduced water-cement ratios compared to rotary drum mixers. 2

10 The water-cement ratio of concrete is very important in relation to concrete permeability. In general concrete becomes less permeable as the water-cement ratio is reduced. Other than water-cement ratio another very important variable that relates to the permeability of concrete is the type of cementitious materials used. The use of supplementary cementitious materials such as fly ash, microsilica or ground granulated blast furnace slag will significantly reduce the permeability of concrete. Slag and microsilica will typically produce concretes with lower permeability than fly ash (particularly at earlier ages). ODOT s high performance concrete mix designs contain these supplementary cementitious materials. The ODOT high performance mix designs are shown in Table A2 (Appendix A). Concrete containing supplementary cementitious materials can possibly have a lower permeability at an increased water-cement ratio compared to a straight cement concrete with a lower water-cement ratio. The use of supplementary cementitious materials is not required of the prestressed/precast manufacturers. The mix design used for the production of the precast bridge components generally contains only Type III portland cement as the cementitious material. Another major difference between the prestressed/precast concrete and cast-in-place concrete used for bridge decks is the curing methods employed. The precasters use a short duration (typically 11 to 18 hr) heat cure, while cast-in-place concrete is typically cured by keeping the surface moist by covering with wet burlap and plastic sheeting for 7 days and then applying a curing compound material. Several studies have shown that heat curing of concrete to temperatures of 70 o C (158 o F) can increase the concrete permeability 4,5,6. Two of the studies 5,6 also concluded that the adverse effect on the permeability caused by the heat curing was mitigated when microsilica was used in the concrete. 3

11 OBJECTIVES This study was designed to determine the permeability of prestressed/precast concrete supplied to ODOT for use as bridge components. The prestressed/precast concrete was tested using the Rapid Chloride Permeability Test method previously described. The Rapid Chloride Permeability Testing was performed at the ages of 14, 28, 56 and 90 days. Tests were performed on 100 mm (4 in.) diameter concrete cores taken from mocked up test sections having the same cross-sectional dimensions as the production component being cast. The test sections were cast and cured along with the production prestressed/precast components. One objective of the study was to determine if the heat curing used by the prestressed/precast manufacturers affects the permeability of the concrete. To determine this, Rapid Chloride Permeability Testing was also performed on 100 x 200 mm (4 x 8 in.) concrete test cylinders that were cast from the same concrete batch as the test sections. These cylinders were not subjected to the heat cure. The test results of these cylinders (ambient cured) were compared to the test results of the concrete cores (heat cured) from the same concrete batch. Another objective was to determine how the permeability of the prestressed/precast concrete compares to the permeability of ODOT s high performance cast-in-place concrete used for bridge deck construction. The permeability results of the current study were compared to permeability results from previous testing performed during ODOT s cast-in-place high performance bridge deck projects. The Rapid Chloride Permeability testing of the cast-in-place deck concrete is performed on laboratory cured 100 x 200 mm (4 x 8 in.) concrete cylinders at the ages of 28, 56 and 90 days. An additional objective of this study was to determine if cylinder specimens tested by the precasters for release strength are representative of the in-place precast concrete strength. To determine this, 4

12 cylinder specimens were prepared and cured along with the test sections. Compressive strength testing was performed on these cylinders at the ages of 1 day and 28 days. Compressive strength testing was also performed at 1 day and 28 days on concrete cores drilled from the precast test sections to compare against the cylinders. WORK PLAN Photographs documenting the various steps of the test program are presented in Appendix B - Figure B1 through Figure B9. Concrete Mix Designs The concrete mix design that each manufacturer uses in the production of prestressed/precast bridge components was supplied to CRT. Depending on the particular project, a calcium nitrite corrosion inhibiting admixture is often used in the concrete mix designs. Calcium nitrite is known to affect the results of the Rapid Chloride Permeability Test. When concrete containing calcium nitrite is used in this test, the concrete will exhibit higher coulomb values when compared to an identical concrete without calcium nitrite. This is because the use of calcium nitrite increases the ionic conductivity of the concrete pore solution. However, testing has shown that the use of calcium nitrite does not affect the actual permeability of concrete. 7 For those manufacturers using this admixture at the time of the testing program it was necessary to prepare concrete batches without calcium nitrite for the preparation of the test specimens. The mix designs used by each of the manufacturers are presented in Table A3. 5

13 Preparation of Test Specimens The study was intended to be performed using prestressed/precast box beams. However, two of the manufacturers who are qualified to produce box beams for ODOT, were not producing box beams at the time of this study. These manufacturers were Tecspan and Prestress Services - Decatur. ODOT decided that these manufacturers should remain as part of the study. Therefore, at these two locations, test sections of I-beams were prepared instead of box beams. The manufacturers use the same concrete mix design to produce both types of bridge components. Two concrete test batches were prepared at each of the prestressed/precast manufacturers. Both concrete batches were prepared on the same day. A precast test section was cast from each test batch. The test sections were typically 1.2 to 1.5 meters long (4-5 ft.) and had the same crosssectional dimensions as the production beam being cast. The test sections were cast in the same bed as the production beams. This was done by placing extra bulkheads at the end of the forms (see Figures B1 and B2). Each of the box beam test sections contained a Styrofoam core (see Figures B1 and B3) similar to the production box beams. One difference is that the Styrofoam was slightly reduced in height so that the thickness of the top layer of concrete was 200 mm (8 in.). The typical thickness of the concrete is 125 mm (5 in.). This was done to allow for a 2 to 1 length/diameter ratio of cores to be tested for compressive strength (the cores have a 100 mm (4 in.) diameter). As each test section was cast, the same concrete was used to cast eight, 100 x 200 mm (4 x 8 in.) test cylinders for use in the Rapid Chloride Permeability Test and four, 150 x 300 mm (6 x 12 in.) test cylinders for use in compressive strength testing. The test cylinders were prepared by following the procedures of ASTM C Standard Practice for Making and Curing Concrete Test Specimens in the Field. 6

14 Information regarding the type of mixer and the method of transporting and placing the concrete for each manufacturer is shown in Table A4. The slump, unit weight and air void content was measured on the fresh concrete for each concrete batch tested. The procedures followed for this testing were: ASTM C Standard Test Method for Slump of Hydraulic-Cement Concrete; ASTM C Standard Test Method for Density (Unit Weight), Yield, and Air Content (Gravimetric) of Concrete; ASTM C Standard Test Method for Air Content of Freshly Mixed Concrete by the Pressure Method. The results of this testing are summarized in Table A5. Curing & Coring of Test Specimens The concrete test sections were cured along with the production beams. The type of curing varied for the different manufacturers. Five of the manufacturers use steam curing, while the other three use different types of radiant heating. The radiant heating was provided by passing either hot oil or hot water through pipes at the base of the casting beds or by the use of gas space heaters. Some of the manufacturers do not use externally applied heat during the warmer months of the year. All of the manufacturers use either plastic tarps or insulated curing blankets to cover the beams during the curing period (see Figure B6). The temperature of the concrete test sections was monitored during the curing period by placing a thermocouple about 7 to 10 cm (2.8 to 3.9 in.) deep into the top surface of the concrete test sections (see Figure B4). The maximum recorded temperatures ranged from 56 o C to 70 o C (133 o F to 158 o F). Table A6 summarizes the type of curing used by each manufacturer and the maximum recorded temperatures. This table also shows which manufacturers did not use externally applied heat for this study. The concrete test sections where external heat was not used, reached similar maximum 7

15 temperatures as the concrete where heat curing was used. Figure 1 (Appendix A) shows graphs of typical temperature curves of the concrete test sections. The test sections were demolded the morning following placement (Figure B7). After demolding, two 100 mm (4 in.) diameter concrete cores were drilled from each test section for 24-hour compressive strength measurements. The cores were drilled from the top finished surface of the box beam test sections and through the web of the I-beam test sections (it was necessary to take the compressive strength cores through the web of the I-beams to obtain the needed core length). The cores were surface dried and placed into sealed plastic bags. The 150 x 300 mm (6 x 12 in.) cylinder specimens (for compressive strength testing) were cured along with the test sections. The 100 x 200 mm (4 x 8 in.) cylinder specimens (for RCPT) were ambient cured overnight (see Table A6). All of the 100 x 200 mm cylinders and two of the 150 x 300 mm cylinders were transferred to CRT in the molds at the age of 1 day. At CRT the cylinders were demolded, labeled and placed in a moist room at o C ( o F) and 100 % humidity until tested. The demolded test sections were stored in outdoor ambient conditions for a period of 7 to 10 days. At this time, ten 100 mm (4 in.) diameter cores were drilled from each test section (8 for RCPT and 2 for compressive strength). All of the cores were taken from the top finished surface of the precast test sections with the exception of the I-beam compressive strength cores, which were taken from the web of the I-beam. After drilling, the surface moisture was removed from the cores and the cores were placed into sealed plastic bags. The cores were then transferred to CRT. The cores were stored at the laboratory (~ 23 o C) in sealed containers until tested. 8

16 Testing of Specimens Compressive Strength Testing The cylinders were tested in accordance with ASTM C Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens. The test cylinders were 150 mm (6 in.) diameter by 300 mm (12 in.) long specimens. For each concrete test batch, two cylinders were tested at the age of 24 hours and two were tested at the age of 28 days. The cores were tested in accordance with ASTM C Standard Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete. The concrete cores have a diameter of 100 mm (4 in.) and a length of roughly 200 mm (8 in.). For each concrete test section prepared, two cores were tested at the age of 24 hours and two were tested at the age of 28 days. The 24-hour compressive strength tests (cylinders and cores) were performed at the prestressed/precast plant. Pad caps were used for all of the 24-hour compressive strength testing. The 28-day compressive strength tests were performed at CRT. Sulfur based capping compound was used for the 28-day strength tests. Rapid Chloride Permeability Testing The concrete cylinder and core specimens were tested in accordance with ASTM C Standard Test Method for Electrical Indication of Concrete's Ability to Resist Chloride Ion Penetration. The specimens were tested at the ages of 14, 28, 56 and 90 days. For each manufacturer at each test age, there were eight specimens tested (two cores and two cylinders from test batch No. 1; two cores and two cylinders from test batch No. 2). The RCPT set up at CRT is shown in Figure B9. 9

17 RESULTS OF TESTING Compressive Strength Testing The results of the compressive strength testing are summarized in Table A7 for the cores and Table A8 for the cylinders. The results show that the test cylinders had similar strengths to the inplace concrete (cores). The 1 day and 28 day strength results are shown graphically in Figure A2. The average strength of all the cores tested at the age of 1 day was 41.4 MPa (6000 psi). The average strength of the 1 day cylinder specimens was 40.2 MPa (5810 psi). At 28 days the cores had an average strength of 51.2 MPa (7420 psi), while the cylinders had an average strength of 52.0 MPa (7530 psi). The concrete at the age of 1 day reached approximately 80 percent of the 28 day strength. The highest strength reached at 28 days was 64.8 MPa (9400 psi). Rapid Chloride Permeability Testing The results of the rapid chloride permeability testing are summarized in Table A9 for the cores and Table A10 for the cylinders. Bar charts of the data are shown in Figure A3. It can be seen from these charts that the test values for one of the manufacturers (United Precast) are significantly higher than the values of the other manufacturers (about 3X higher). It is believed that the concrete used for the test sections at United Precast was not representative of the concrete used for the production box beams. This is based on the fact that the strengths of the concrete used for the test sections was lower than the strengths measured on the production concrete. The very high permeability values measured on the United Precast concrete is most likely due to a higher than intended water-cement ratio. 10

18 The United Precast permeability data was not used in calculating average test values for this study. Figure A4 shows the same bar graphs excluding the data from United Precast. The same data is also shown using line graphs in Figure A5. These graphs give a good indication of the relative performance of the various manufacturers. The average permeability values of the cores compared to the cylinders is shown below (excludes UP data). As can be seen from the data, the average value for the cores is slightly lower compared to the average value for the cylinders (no difference at 90 days). However, when looking at the data from the individual manufacturers, the cores have lower permeability values than the cylinders in some cases, while in other cases the cylinders have lower permeability values than the cores. The data shown below comparing the average test results of the cores versus the cylinders is shown graphically in Figure A6. This figure also has a graph showing the data from one of the individual manufacturers. Average coulomb value of all the specimens tested (excluding UP data) for each test date. Test Age Cores Cylinders Difference % Difference 14 days 2,750 3, days 2,080 2, days 1,680 1, days 1,430 1, Effect of Heat Curing One objective of this study was to determine if the heat cure of the precast bridge components increases the permeability of the concrete. The test results show that the concrete represented by the heat cured test sections had similar permeability values compared to the concrete that was ambient 11

19 cured (cylinders). Therefore, for the conditions of the present study, the heat curing of the precast concrete did not have an adverse effect on the concrete permeability. This finding is contrary to previous laboratory studies, 4,5,6 which showed that heat curing of concrete to temperatures of 70 o C (158 o F) increased the permeability compared to concretes cured at 23 o C (73 o F). Comparison of Precast Concrete to ODOT High Performance Cast-In-Place Concrete Rapid Chloride Permeability Test data from ODOT s high performance cast-in-place bridge deck projects was supplied to CRT by ODOT personnel. The ODOT permeability data used to compare against the results of the current study included the 90 day test results from the years of 1998 through This data includes 69 bridge projects using ODOT HPC Mix No. 3 and 111 bridge projects using ODOT HPC Mix No. 4. This data is summarized below and compared with the 90 day cylinder tests from the current study. Rapid Chloride Permeability Data From ODOT s High Performance Bridge Deck Concrete (1998 Through day test data) ODOT Mix Number of Bridge Decks Average Coulomb Value Standard Deviation, 1σ Range No to 1380 No to 890 Rapid Chloride Permeability Data From CRT Study (90 day test data - Cylinders) Specimen Type Number of Tests Average Coulomb Value Standard Deviation, 1σ Range Cylinders 14 1, to

20 The concrete mix designs used for the prestressed/precast concrete contain only Type III cement as the cementitious component. The ODOT mix designs however, contain Type I cement along with supplementary cementitious materials. Mix No. 3 contains fly ash and silica fume while Mix No. 4 contains GGBF slag and silica fume (see Table A2). As can be seen from the above data, the average permeability of the cast-in-place concrete is significantly lower than the precast concrete. This shows that the supplementary cementitious materials have a very large impact on the permeability of the concrete. Even though the precast concrete has lower water-cementitious ratios compared to the cast-in-place concrete, the permeability of the precast concrete is higher. However, it is possible for the precast concrete manufacturers to produce concrete with a very low permeability (< 1000 coulombs). Several of the precast manufacturers achieved permeability values of less than 1000 coulombs at 90 days. The fact that all of the precasters did not achieve these low permeability values may indicate that the water-cement ratio of the concrete produced exceeded the intended values. The lowest permeability values from the precast concrete (880 to 900 Coulombs) are slightly higher than the average value of ODOT s Mix No. 3. These values however are at the high end of the range of ODOT s Mix No. 4. To consistently produce precast concrete with permeability values similar to ODOT s High Performance Mix No. 4, it would be necessary to use supplementary cementitious materials. 13

21 CONCLUSIONS 1. Compressive strength testing of concrete cylinders by the prestressed/precast manufacturers gives a good indication of the in-place strength of the precast concrete at both 1 day and at 28 days. 2. The heat curing of the precast concrete did not increase the permeability of the concrete relative to concrete that was ambient cured. 3. The permeability of ODOT s cast-in-place high performance concrete containing supplementary cementitious materials is lower than the permeability of the prestressed/precast concrete containing straight Type III portland cement. 4. The concretes produced by the different prestressed/precast manufacturers showed large differences in permeability. 5. It is possible for the prestressed/precast concrete manufacturers to produce very low permeability concrete (< 1000 Coulombs) with a straight Type III cement mix if the water-cement ratio of the concrete is kept very low (< 0.35). 6. To produce concrete with the lowest possible permeability, supplementary cementitious materials (ie. microsilica, GGBF slag, fly ash) should be used. RECOMMENDATIONS 1. To consistently receive very low permeability concrete, ODOT should consider implementing a permeability specification for their prestressed/precast manufacturers or should require the use of supplementary cementitious materials in the concrete mix designs used for prestressed/precast concrete. 2. Based on the findings of the of the current project, consideration should be given to reevaluating the AASHTO/ACI specifications that allow prestressed/precast concrete to have a reduced concrete cover over the reinforcing steel compared to cast-in-place concrete. Nick Scaglione, President Concrete Research & Testing, LLC 14

22 REFERENCES 1 AASHTO Standard Specification for Highway Bridges, Chapter 8 - Reinforced Concrete, Section 8.22; Chapter 9 - Prestressed Concrete, Section ACI Manual of Concrete Practice, 2001, Part 3, ACI Building Code Requirements for Structural Concrete, Section PCI (Prestressed/Precast Concrete Industry) Bridge Design Manual, Chapter 2 - Material Properties, Section Durability, Section Concrete Cover. 4 R. J. Detwiler, K. O. Kjellsen, O. E. Gjorv, Resistance to Chloride Intrusion of Concrete Cured at Different Temperatures, ACI Materials Journal, January-February, 1991, pp R. J. Detwiler, C. A. Fapohunda, J. Natale, Use of Supplementary Cementing Materials to Increase the Resistance to Chloride Ion Penetration of Concretes Cured at Elevated Temperatures, ACI Materials Journal, January-February, 1994, pp R. D. Hooton, P. Pun, T. Kojundic, P. Fidjestol, Influence of Silica Fume on Chloride Resistance of Concrete, Proceedings of the PCI/FHWA International Symposium on High Performance Concrete, New Orleans, LA, October 20-22, Standard Method of Test for Electrical Indication of Concrete s Ability to Resist Chloride, AASHTO Designation: T , Section

23 Appendix A

24 Table A1. List of ODOT pre-qualified manufacturers of prestressed/precast box beams. The code used by CRT for the identification of test specimens produced from each manufacturer is provided (these codes are used in many of the following tables and charts to identify the manufacturers). Manufacturer Location Code Carr Concrete Waverly, WV CC Marietta Structures Corp. Marietta, OH MS Prestress Services, Inc. Decatur, IN PD Prestress Services, Inc. Melbourne, KY PM Prestress Services, Inc. Lexington, KY PL Stress-Con Industries, Inc. Bay City, MI SC Tecspan Concrete Structures, Inc.* Grove City, OH TS United Precast, Inc. Mt. Vernon, OH UP *This company is now Prestress Services of Ohio. Note: Manufacturers are listed in alphabetical order. A-1

25 Table A2. Ohio Department of Transportation High Performance Concrete Mix Designs Used for Bridge Deck Construction (from Supplemental Specification 844). Constituent Weight, kg/m 3 (lb/yd 3 ) Mix 3 Mix 4 Portland Cement Class C Fly Ash 285 (480) 89 (150) 261 (440) ---- GGBF Slag (190) Microsilica Total Cementitious Fine Aggregate No. 8 Coarse Aggregate* 18 (30) 392 (660) 792 (1,355) 884 (1,490) 18 (30) 392 (660) 813 (1,370) 884 (1,490) Maximum Water-Cementitious Ratio *Weights are based on Crushed Limestone A-2

26 Table A3. Concrete Mix Designs used for each of the prestressed/precast manufacturers. Constituent Weight, kg/m 3 (lb/yd 3 ) CC MS PD PL PM SC TS UP Type III Portland Cement 418 (705) 418 (705) 446 (752) 435 (733) 390 (658) 446 (752) 445 (750) 390 (658) Fine Aggregate 643 (1084) 609 (1026) 654 (1103) 697 (1175) 669 (1128) 801 (1350) 828 (1395) 783 (1320) Coarse Aggregate 1023 (1725) 1093 (1843) 1068 (1800) 1061 (1788) 1166 (1965) 1009 (1700) 871 (1468) 943 (1590) A-3 Water-Cement Ratio Coarse Aggregate Type No. 8 Gravel No. 8 Gravel No. 67 Limestone No. 67 Limestone No. 8 Gravel No. 67 Limestone No. 8 Limestone No. 57 Limestone Note: Admixtures used are not shown. Note: The above weights are designed values (SSD weights) and are not necessarily the actual weights used during the casti ng of the test specimens.

27 Table A4. Mixer type, method of transporting and placing concrete and vibration methods used for each of the prestressed/precast manufacturers. Manufacturer Mixer Type Transport/Placement of Concrete Method of Consolidation Carr Concrete 4 yd 3 Ribbon Mixer* Hopper and Crane Immersion Vibrators Marietta Structures Ready Mix Trucks Ready Mix Trucks Immersion Vibrators Prestress Services - Decatur, IN 4 yd 3 Pan Mixer Ready Mix Trucks Immersion Vibrators A-4 Prestress Services - Lexington, KY 4 yd 3 Pan Mixer Ready Mix Trucks Immersion Vibrators and Form Vibrators Prestress Services - Melbourne, KY 6 yd 3 Ribbon Mixer* Hopper Trucks (Tuckerbuilt) Immersion Vibrators Stress-Con Industries Large Central Mix Drum at off site ready mix plant Ready Mix Trucks Immersion Vibrators and Form Vibrators Tecspan Concrete Structures Large Central Mix Drum at off site ready mix plant Ready Mix Trucks/ Hopper and Crane Immersion Vibrators and Form Vibrators United Precast Ready Mix Trucks Ready Mix Trucks Immersion Vibrators *Horizontal stationary drum with blades moving through the concrete.

28 Table A5. Fresh concrete properties measured on each of the test mixes. Manufacturer Date Cast Air, % Unit Weight, kg/m 3 (lb/ft 3 ) Slump, mm (in.) Mix 1 Mix 2 Mix 1 Mix 2 Mix 1 Mix 2 Carr Concrete (144.9) 2297 (143.4) 76 (3) 83 (3 ¼) Marietta Structures (142.1) 2326 (145.2) 190 (7 ½) 127 (5) Prestress Services - Decatur, IN (147.4) 2400 (149.8) 216 (8 ½) 121 (4 ¾) Prestress Services - Lexington, KY (146.2) 2396 (149.6) 184 (7 ¼) 190 (7 ½) A-5 Prestress Services - Melbourne, KY (147.4) 2372 (148.1) 184 (7 ¼) 184 (7 ¼) Stress-Con Industries (149.0) 2385 (148.9) 190 (7 ½) 203 (8) Tecspan Concrete Structures (145.1) 2328 (145.3) 222 (8 ¾) 184 (7 ¼) United Precast (143.9) 2289 (142.9) 190 (7 ½) 140 (5 ½) Note: The manufacturers are listed in order of the date the test sections were produced.

29 Table A6. Summary of Curing Information for Each of the Prestressed/Precast Manufacturers. Manufacturer Date Cast Ambient Temp. During Casting, o C ( o F) Type of Heat Cure Heat Cure Used Max. Temp. Recorded, o C ( o F) Carr Concrete (80) Hot Water No 66 (151) Marietta Structures (90) Hot Oil Yes 61 (141) Prestress Services - Decatur, IN (75) Steam Yes 70 (158) Prestress Services - Lexington, KY (48) Steam Yes 56 (133) A-6 Prestress Services - Melbourne, KY (80) Steam Yes 64 (148) Stress-Con Industries (52) Space Heaters Yes 62 (143) Tecspan Concrete Structures (90) Steam No 66 (151) United Precast (80) Steam No 64 (148) Notes: The casting beds at Carr Concrete and Stress-Con were located in open air buildings, while the casting beds of the other manufacturers were located outdoors. The 100 x 200 mm (4 x 8 in.) test cylinders were cured overnight in open air buildings at each manufacturer.

30 Recorded Temperatures of Concrete Test Section Marietta Structures - Marietta, OH Temperature, C Temperature, F Mix Time, hours Recorded Temperatures of Concrete Test Sections Tecspan - Grove City, OH Temperature, C Temperature, F Mix 1 Mix Time, hours Figure A1. Typical temperature curves of Precast concrete test sections. A-7

31 Table A7. Compressive Strength Test Results of Concrete Cores. Specimen I.D. Compressive Strength, MPa (psi) 1 day 28 days CC (6150) 44.9 (6510) CC (5810) 44.0 (6380) MS (6500) 45.4 (6590)* MS (5020) 46.6 (6750)* PD (8180) 64.8 (9400) PD (8260) 62.1 (9010) PL (6380) 57.0 (8260) PL (7410) 62.1 (9010) PM (5870) 51.4 (7450) PM (5240) 48.3 (7010) SC (5610) 53.8 (7800) SC (5550) 53.4 (7750) TS (6500) 61.3 (8890) TS (5300) 46.1 (6690) U (4350) 40.4 (5860) UP (3930) 36.6 (5310) Average 41.4 (6000) 51.2 (7420) *37 day test Note: Each value is the average of 2 test specimens. A-8

32 Table A8. Compressive Strength Test Results of Concrete Cylinders. Specimen I.D. Compressive Strength, MPa (psi) 1 day 28 days CC (5770) 51.0 (7400) CC (5710) 50.5 (7320) MS (5130) 44.6 (6460)* MS (5290) 43.3 (6280)* PD (7300) 62.2 (9020) PD (7600) 61.2 (8880) PL (6070) 56.5 (8190) PL (7610) 64.8 (9400) PM (5680) 54.3 (7880) PM (5550) 49.7 (7210) SC (5810) 53.8 (7800) SC (6020) 55.8 (8090) TS (6200) 56.3 (8170) TS (6140) 55.2 (8000) UP (3750) 37.7 (5470) UP (3380) 34.3 (4970) Average 40.1 (5810) 52.0 (7530) *37 day test Note: Each value is the average of 2 test specimens. A-9

33 1 day Compressive Strength Test Results Compressive Strength, MPa Compressive Strength, psi Core Cylinder 0 0 CC-1 CC-2 MS-1 MS-2 PD-1 PD-2 PL-1 PL-2 PM-1 PM-2 SC-1 SC-2 TS-1 TS-2 UP-1 UP-2 Manufacturer 28 day Compressive Strength Test Results Compressive Strength, MPa CC-1 CC-2 MS-1 MS-2 PD-1 PD-2 PL-1 PL-2 PM-1 PM-2 SC-1 SC-2 TS-1 TS-2 UP-1 UP Compressive Strength, psi Core Cylinder 0 Manufacturer Figure A2. Compressive Strength Test Results of Concrete Cores and Cylinders. A-10

34 Table A9. Rapid Chloride Permeability Test Results of Concrete Cores. Specimen I.D. Total Charge Passed, Coulombs 14 days 28 days 56 days 90 days CC 1 3,050 2,410 2,250 2,000 CC 2 3,420 2,840 2,630 2,040 MS 1 2,670 2,470 2,350 1,860 MS 2 3,860 3,240 3,200 2,630 PD 1 2,740 1,360 1, PD 2 2,500 1,330 1, PL 1 1,730 1, PL 2 1,900 1, PM 1 2,650 1,890 1,310 1,080 PM 2 2,820 2,100 1,120 1,040 SC 1 3,150 2,690 1,760 1,410 SC 2 2,620 1,930 1,400 1,380 TS 1 2,570 1,960 1,510 1,480 TS 2 2,780 2,220 1,850 1,680 UP 1 9,200 7,460 5,600 4,880 UP 2 8,700 6,860 6,020 4,500 Note: Each value is the average of 2 test specimens. A-11

35 Table A10. Rapid Chloride Permeability Test Results of Concrete Cylinders. Specimen I.D. Total Charge Passed, Coulombs 14 days 28 days 56 days 90 days CC 1 3,390 2,530 2,400 2,200 CC 2 3,370 2,570 2,440 2,190 MS 1 4,210 2,940 2,600 2,140 MS 2 3,610 3,000 2,740 2,370 PD 1 3,780 2,020 1, PD 2 3,200 1,740 1, PL 1 2,130 1,530 1, PL 2 2,200 1,720 1, PM 1 2,750 1,950 1, PM 2 2,740 1,890 1, SC 1 2,530 1,790 1, SC 2 2,690 1,650 1, TS 1 3,120 2,500 2,160 1,920 TS 2 3,230 2,440 2,040 1,910 UP 1 10,210 7,040 4,230 3,970 UP 2 9,080 6,170 4,050 3,280 Note: Each value is the average of 2 test specimens. A-12

36 9000 Rapid Chloride Permeability Test Results Cores Charge Passed, Coulombs days 28 days 56 days 90 days CC MS PL PD PM SC TS UP Manufacturer Charge Passed, Coulombs Rapid Chloride Permeability Test Results Cylinders CC MS PL PD PM SC TS UP Manufacturer 14 days 28 days 56 days 90 days Figure A3. Rapid Chloride Permeability Test Results of Concrete Cores and Cylinders. A-13

37 Rapid Chloride Permeability Test Results Cores Charge Passed, Coulombs CC MS PL PD PM SC TS Manufacturer 14 days 28 days 56 days 90 days Charge Passed, Coulombs Rapid Chloride Permeability Test Results Cylinders CC MS PL PD PM SC TS Manufacturer 14 days 28 days 56 days 90 days Figure A4. Rapid Chloride Permeability Test Results of Concrete Cores and Cylinders excluding the United Precast data. A-14

38 Charge Passed, Coulombs Rapid Chloride Permeability Test Results Cores Age, days CC MS PL PD PM SC TS Charge Passed, Coulombs Rapid Chloride Permeability Test Results Cylinders Age, days CC MS PL PD PM SC TS Figure A5. Rapid Chloride Permeability Test Results of Concrete Cores and Cylinders excluding the United Precast data. A-15

39 Rapid Chloride Permeability Test Results Prestress Services - Decatur Charge Passed, Coulombs Age, days PD-1 core PD-2 core PD-1 cyl PD-2 cyl Charge Passed, Coulombs Rapid Chloride Permeability Test Results Cores vs. Cylinders Age, days Cores Cylinders Figure A6. Rapid Chloride Permeability Test Results. The upper chart is a comparison of the cores vs. the cylinders for one of the manufacturers, showing individual data points for each concrete test batch. The lower chart compares the average values of the cores and the cylinders for all of the manufacturers (excluding UP). A-16

40 Appendix B

41 Figure B1. Bulkheads placed in the box beam forms to produce the 1.5 meter (5 ft.) long test sections. The Styrofoam cores to be placed in the test sections are shown in the lower photograph. Upper photograph taken at Carr Concrete. Lower photograph taken at Marietta Structures. B-1

42 Figure B2. Bulkheads placed in the box beam form to produce one of the test sections. The lower photograph shows the inside of the test section. Plastic sheaths were placed over the prestressing steel. Photographs taken at Prestress Services - Decatur Plant. B-2

43 Figure B3. Casting of box beam test sections at Carr Concrete. The concrete was mixed in an on-sight ribbon mixer and delivered to the form by an overhead crane and bucket. B-3

44 Figure B4. The upper photograph shows the casting of the box beam test sections at United Precast. The concrete was mixed at an on-sight ready mix plant and delivered to the form by ready mix trucks. The lower photograph shows the temperature monitoring of the two finished precast test sections. B-4

45 Figure B5. The upper photograph shows the sampling of concrete from the middle of the batch for the casting of test cylinders and measurement of the fresh concrete properties. The lower photograph shows the casting of the test cylinders. The photographs were taken at Carr Concrete. B-5

46 Figure B6. Curing of the box beams at Marietta Structures. After the casting was complete, the box beams were first covered with plastic tarps and then covered with a curing blanket. B-6

47 Figure B7. Removal of the test sections from the molds the morning after casting. The upper photograph was taken at Marietta Structures. The lower photograph was taken at Carr Concrete. B-7

48 Figure B8. Coring of box beam test sections at Prestress Services - Decatur Plant. The production box beam can be seen in the background (length = 39.6 meters ft.). B-8

49 Figure B9. Testing of the concrete. The upper photograph shows compressive strength testing of a concrete core at Carr Concrete. Pad caps were used for the 1 day compressive strength testing at the precast plants. The lower photograph shows the Rapid Chloride Permeability Test being performed at CRT (90 day testing of Stress-Con specimens - 4 cylinders and 4 cores). B-9