Ozyildirim and Moruza 1 RECENT VDOT APPLICATIONS WITH SELF-CONSOLIDATING CONCRETE

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1 Ozyildirim and Moruza 1 RECENT VDOT APPLICATIONS WITH SELF-CONSOLIDATING CONCRETE H. Celik Ozyildirim, Ph.D., P.E. Principal Research Scientist Virginia Center for Transportation Innovation and Research 530 Edgemont Road Charlottesville, VA Telephone: (434) Fax: (434) celik@vdot.virginia.gov Gail M. Moruza Research Assistant Virginia Center for Transportation Innovation and Research 530 Edgemont Road Charlottesville, VA Telephone: (434) Fax: (434) Gail.Moruza@vdot.virginia.gov Corresponding Author: H. Celik Ozyildirim Word Count: 3, Tables + 5 Figures = 5,284

2 Ozyildirim and Moruza 2 ABSTRACT Self-consolidating concrete (SCC) exhibits very high workability as it easily fills the congested spaces between the reinforcement (both mild reinforcement and prestressing steel) and formwork under the influence of its own mass without the use of any additional consolidation energy. This paper reviews the use of SCC by the Virginia Department of Transportation in both cast-in-place and precast applications such as repairs, pier cap placements, and beams with both normal weight and lightweight concretes. Both completed and ongoing studies indicate that SCC, whether in cast-in-place or precast applications, can be successfully used in bridge structures. These practices should be followed: care should be exercised with workability retention during the project to avoid consolidation issues; forms should be secured; concrete should be placed in forms in incremental heights to prevent bulging and failure; a proper mix design with fines should be ensured for flowability and stability; viscosity-modifying admixtures should be added for stability; and proper setting times for timely finishing operations should be established.

3 Ozyildirim and Moruza 3 INTRODUCTION A fundamental property of self-consolidating concrete (SCC) is its very high level of workability (1). SCC easily fills the congested spaces between the reinforcement (both mild reinforcement and prestressing steel) and formwork under the influence of its own mass and without the use of any additional consolidation energy. Inherent properties of SCC eliminate large air voids, enhancing the strength and reducing the permeability of the concrete, which is essential for longevity. In conventional concrete, consolidation would be needed to eliminate large air voids. Easily flowing SCC permits convenient and fast concrete placement. SCC has been successfully used in Japan and Europe since the early 1990s (2). Some of the benefits of SCC are reduced labor; increased construction speed; improved mechanical properties and durability characteristics; ease of placement in the heavily reinforced and congested areas common in beams with strands and shear reinforcement; consolidation without vibration and without segregation; and a reduced noise level at manufacturing plants and construction sites (1). There are some concerns with SCC including the degree of uniformity, the potential for segregation, increased shrinkage, the quality of the air-void system, and the quality of the bond between strands and concrete. However, the bond strength of SCC at 28 days has been shown to be greater (at an increase of 16% to 40%) than that of a mixture with normal workability (3). In the United States, the precast industry has been using SCC in regular production since 2000 (1, 4). In 2002, 40% of precast manufacturers in the United States had used SCC. In 2003, 2.3 million yd 3 were used in the precast industry (1). On the other hand, the use of SCC in the ready mixed concrete industry had a slower start in the United States, with estimated production in 2002 limited to 130,000 cubic yards (1, 5). Today, most producers of precast elements are using and seeing the advantages of SCC, and cast-in-place applications have also started to increase. Forms need to be tight and sturdy. SCC can flow through small openings, and because of the high fluidity of the mixture, high hydrostatic pressures can occur and cause bulging and failure of the forms (6). However, the form pressures measured in the field were much lower than the hydrostatic pressure (6, 7). This reduction is attributed to SCC s thixotropic properties, which indicates that SCC stiffens when it is at rest, reducing the pressure exerted. Increasing the casting rate increases the form pressure. Billberg et al. (6) found that for a delivery time of 30 minutes, the form pressure was considerably lower than the design values up to a casting rate of approximately 6.5 feet per hour. Tejeda-Dominguez et al. (7) found that at slow rates less than 9 feet per hour in high walls, hydrostatic pressure was not achieved. ACI 347, Guide to Formwork for Concrete (8), does not have any special provisions for SCC; thus, users consider hydrostatic pressure unless tests are conducted to justify the use of lower pressure (7). The formwork pressures can be determined using pressure devices. Models are also available to predict the lateral form pressure exerted by SCC (9, 10). The method of filling the formwork whether filling from the top or pumping from the base of the formwork affects the lateral form pressures developed (11). When the formwork is filled by pumping from the bottom up, SCC needs to stay fluid during the placement and exert high pressures. Formwork designs that accommodate the expected liquid head formwork pressures can allow unrestricted placement rates, be economical, and permit the contractor to

4 Ozyildirim and Moruza 4 take full advantage of a fast casting rate for the SCC. To allow a better understanding of the lateral pressures needed to optimize the formwork design, pressure devices or models can be used. The first application of SCC in a bridge structure in Virginia was in 2001, with the construction of a BEBO arch bridge in Fredericksburg (12). Twenty-five precast arch segments were placed side by side to create a single 30-foot span across a creek. Since then, the Virginia Department of Transportation (VDOT) has been using SCC in precast applications such as beams and in cast-in-place applications such as drilled shafts. In beams, the first application was in 2008 in the Pamunkey River Bridge at West Point (13). The successful completion of the bridge led to the acceptance of SCC in future VDOT projects. The first application in drilled shafts was in the Route 28 Bridge in Manassas (14). The successful completion of this bridge led to VDOT s special provision that requires SCC in all new drilled shafts in Virginia. PURPOSE AND SCOPE The purpose of this paper is to present recent applications of SCC in cast-in-place and precast applications in Virginia. 1. Cast-in-place applications include repairs of substructures and construction of new pier caps. In repairs of columns and pier caps, concrete was placed in a thin depth behind the forms. Repairs of substructures were made at Altavista and Alma. In new pier caps at Virginia Beach, a large exposed surface area with a slope and raised areas for the beam seats were present. At Virginia Beach, three new pier caps were cast at the Nimmo Parkway Bridge over the West Neck Creek. 2. Precast applications include beams with normal weight and lightweight concretes. At the two Nimmo Parkway bridges over the West Neck Creek and the Hunt Club Tributary, 220 normal weight concrete beams were placed. At Opal, 8 lightweight concrete beams were placed. CAST-IN-PLACE APPLICATIONS Repairs Route 699 and Route 712 VDOT s first repair project was in Altavista in the Lynchburg District in 2010 where bridges on Route 699 and Route 712 were repaired with SCC instead of the routine shotcrete (Figure 1). Concrete was dropped using a funnel or placed using buckets. However, placement by buckets did not provide the pressure head needed for the SCC to flow through the tight areas and congested reinforcement. In addition, delays caused premature stiffening and hindered flow, so vibrators were used to make the concrete flow. Further, form bulging was encountered that required better securing of forms to the structure. The concrete mixture proportions given in Table 1 show a large amount of fines to achieve a stable mixture. Commercially available airentraining and high-range water-reducing admixtures (HRWRA) were used to provide higher workability. In addition, workability-retaining admixture was tried successfully to maintain the slump flow. Concrete strengths of over 5,000 psi were achieved and were acceptable as the values were above the specified minimum of 3,000 psi. Low permeability below 2000 C was

5 Ozyildirim and Moruza 5 obtained at 28 days using accelerated curing. Permeability specimens were subjected to accelerated curing; specimens were kept moist at room temperature for 1 week and then 3 weeks at 100 F. FIGURE 1 Repaired backwall on Route 699 (left) and substructure on Route 712 (right). TABLE 1 Concrete Mixture Proportions (lb/yd 3 ) Material Routes 699 and 712 Route 340 Cement Fly ash Coarse aggregate 1,323 1,414 Fine aggregate 1,220 1,364 Maximum water content Water cementitious material ratio Route 340 A more recent application of SCC repair was in 2013 on Route 340 over the south fork of the Shenandoah River near Alma (Figure 2). The concrete was removed from the areas marked for repair prior to placement of the forms and SCC. The Route 340 Bridge has six piers, three of which were repaired using SCC. The proportions of the concrete mixture are shown in Table 1. In addition, 4 gallons of calcium nitrite per cubic yard was used to provide conductivity for the anodes installed. Anodes were used for corrosion protection, and investigations are ongoing to determine if they are cost-effective. Commercially available air-entraining, retarding, and HRWRAs were used. Retarding admixture enabled the retention of slump flow. Slump flow values were obtained as the truck arrived at the job site and also as it was leaving. Concretes were self-consolidating throughout the placement and did not require vibration. Bulging of the forms attributable to form pressure occurred at the beginning. Forms were secured better in the following placements; placement was made in increments of 8 feet to minimize high form pressure. Strengths exceeding 5,000 psi and permeability below 1500 C were obtained even with the addition of 4 gallons of calcium nitrite per cubic yard. As stated in ASTM 1202, calcium nitrite interferes with this electrical test indicating higher coulomb values then identical concrete mixtures without the calcium nitrite.

6 Ozyildirim and Moruza 6 FIGURE 2 Route 340 Bridge (left) during construction (right). New Pier Caps In this application, the length of the pier cap was 58 feet. The trucks parked at the completed bridge next to the pier cap (Figure 3). Concrete was discharged into the chutes and flowed from one end to the other in the pier cap. The pier cap minimum compressive strength was 3,000 psi and the maximum permeability was 2500 C. The concrete mixture proportions are shown in Table 2. A viscosity-modifying admixture (VMA) was added for stability. Limited internal vibration was conducted when slump flow was at or below 20 inches. On the first day of placement, the mixture contained a retarding admixture that worked well with the HRWRA and provided good workability. However, finishers noticed that the concrete was not setting; in fact, the top surface of the cap was still not rigid the next morning. FIGURE 3 New pier cap (left) and the beams with normal weight concrete (right). TABLE 2 General Concrete Mixture Proportions (lb/yd 3 ) Ingredient Pier Cap Normal Weight Beam Lightweight Beam Portland cement Fly ash Normal weight coarse aggregate 1,700 1, Lightweight coarse aggregate Fine aggregate 1,321 1, Water Water cementitious material ratio Air (%)

7 Ozyildirim and Moruza 7 The weather was cool, about 50 F, during placement and in the 40s at night. In addition, one of the four loads exhibited marginal stability. For the pier caps that followed, the retarding admixture was replaced by a water-reducing admixture; the dosage of the HRWRA was reduced; and the dosage of the VMA was increased. In addition, a low dosage of an accelerator was added to prevent delay in setting and help the finishers. Concrete strengths exceeded 6,000 psi at 28 days except for the mixture that showed marginal stability, which had strength of about 5,000 psi. A vertical section of the cylinder in the sample representing marginal stability showed a deep paste layer 1/8 to 3/16 inch deep on the top surface. However, the aggregate distribution within the specimens did not indicate any discernible segregation. PRECAST APPLICATIONS Normal Weight SCC As mentioned previously, the two bridges at the Nimmo Parkway have 220 beams (Figure 3); they are in the same project and are located close to each other just south of Virginia Beach. The specified minimum 28-day compressive strength for beams was 8,000 psi, with a release strength of 6,000 psi and a maximum permeability of 1500 C. The beams and the specimens were steam cured. The concrete mixture proportions are shown in Table 2. Type III portland cement was used. The coarse aggregate used was No. 68 stone. The fine aggregate was natural sand. Admixtures used included an air-entraining admixture, a retarding admixture, and an HRWRA. The strength values summarized in Table 3 indicate satisfactory strengths with low variability. Specimens were steam cured in the bed. The next day, release strengths exceeded the specified value of 6,000 psi. The 8,000 psi specified at 28 days was achieved at 7 days; therefore, 28-day tests were not conducted. The limited permeability tests for this mix design (five specimens) indicated an average permeability of 270 C, which is very low. TABLE 3 Concrete Strengths of Beams with Normal Weight Aggregate Live End Dead End Average Age Strength Strength Strength (days) n (psi) SD n (psi) SD n (psi) SD , , , , , , Live End and Dead End indicate the location in the casting bed; SD = standard deviation; n = number of strength values. Lightweight SCC The bridge structure (Figure 4) on Route 17 over Routes 15/29 in Fauquier County has two spans, each 128 feet long, made continuous for live load with a cast-in-place pier diaphragm. The bridge has a 27-degree skew. In each span, there are four 61-inch-deep bulb T beams with a length of 127 feet 6 inches. The beams have lightweight SCC with slag cement. The deck of this bridge also has lightweight concrete. The lightweight high-performance concrete for the beams had a target unit weight of 120 lb/ft 3 with a maximum acceptable value of lb/ft 3. The strength and permeability requirements were the same as for the normal weight concrete beams.

8 Ozyildirim and Moruza 8 FIGURE 4 Bridge with lightweight SCC beams. The concrete mixture proportions are given in Table 2. Type III cement was used. Normal weight and lightweight coarse aggregates (No. 68) were added. The mixture contained an air-entraining admixture, a water-reducing and retarding admixture, and an HRWRA. It also had 2 gallons of calcium nitrite per cubic yard. The slump flow values with and without the J- ring (Figure 5) were within 1 inch, and there was no segregation. The concrete exhibited a slump flow loss of 2 inches (from 29 to 27 inches) within 10 minutes. The placement of the concrete into beam molds from batching was accomplished within 4 to 5 minutes. Thus, the slump flow loss was not an issue in the production of the beams. The beams were covered with an insulating blanket and cured overnight using a radiant heat cure until the release strength was achieved. The specimens were placed on top of the beams inside the insulating blankets. For the eight batches tested, the slump flow ranged from 24.5 to 28 inches. The compressive strengths at 28 days ranged from 8,592 psi to 11,684 psi, with an average value of 10,723 psi. Permeability test results for two batches averaged 765 C, even in the presence of the calcium nitrite. FIGURE 5 Slump flow tests for SCC with and without J-ring.

9 Ozyildirim and Moruza 9 CONCLUSIONS SCC with high workability and satisfactory strength and permeability can be produced using normal weight or lightweight aggregates. Care should be exercised to prevent segregation in the SCC. Stable mixtures can be achieved with proper mix designs having sufficient fines and VMAs. SCC needs head pressure to flow through tight areas and congested reinforcement. Forms should be strong and secured tightly to the structure. It may be necessary to place the SCC in increments to prevent high form pressures. Slump loss has been an issue in the early applications of SCC. Emphasizing that the concrete needs to be SCC not only in the beginning of a project but also during the construction of a project has led to improvements and satisfactory workability during construction. Retarding and workability-retaining admixtures have been used successfully. In the lightweight SCC project, fast placement between batching and placement in the forms overcame the slump loss issue. Limited internal and external vibration has been used to facilitate flow. Accelerators help to minimize the time of setting, providing timely finishing operations especially in cold weather. ACKNOWLEDGMENTS The authors thank the Virginia Center for Transportation Innovation and Research, the Virginia Department of Transportation, and the Federal Highway Administration for their support of work in developing and implementing SCC. REFERENCES 1. American Concrete Institute. ACI 237: Self-Consolidating Concrete. Farmington Hills, Mich., Okamura, H., and M. Ouchi. Self-Compacting Concrete: Development, Present Use and Future. In Self-Compacting Concrete: Proceedings of the First International RILEM Symposium, A. Skarendahl, and O. Petersson, Eds. RILEM Publications, Cachan Cedex, France, Sonebi, M., and P. J. M. Bartos. Hardened SCC and Its Bond With Reinforcement. In Self- Compacting Concrete: Proceedings of the First International RILEM Symposium, A. Skarendahl, and O. Petersson, Eds. RILEM Publications, Cachan Cedex, France, 1999, pp Schindler, A. K., R. W. Barnes, J. B. Roberts, and S. Rodriguez. Properties of Self- Consolidating Concrete for Prestressed Members. ACI Materials Journal, Vol. 104, No. 1, January-February 2007, p Vachon, M., and J. Daczko. U.S. Regulatory Work on SCC. In Proceedings of the First North American Conference on the Design and Use of SCC. ACBM, Chicago, November 12-13, 2002, pp Billberg, P., J. Silfwerbrand, and T. Osterberg. Form Pressures Generated by Self- Consolidating Concrete. Concrete International, Vol. 27, No. 10, October 2005, pp

10 Ozyildirim and Moruza Tejeda-Dominguez, F., D. A. Lange, and M. D. D Ambrosia. Formwork Pressure of Self- Consolidating Concrete for Tall Wall Field Applications. In Transportation Research Record: Journal of the Transportation Research Board, No. 1914, Transportation Research Board of the National Academies, Washington, D.C., 2005, pp American Concrete Institute. ACI 347: Guide to Formwork for Concrete. Farmington Hills, Mich., Omran, A. F., and K. H. Khayat. Portable Pressure Device to Evaluate Lateral Formwork Pressure Exerted by Fresh Concrete. Journal of Materials in Civil Engineering, Vol. 25, No. 6, June 2013, pp Gardner, N. J., L. Keller, R. Quattrociocchi, and G. Charitou. Field Investigation of Formwork Pressures Using Self-Consolidating Concrete. Concrete International, Vol. 34, No. 1, January 2012, pp Serge Tichko, S., J. Van De Maele, N. Vanmassenhove, G. De Schutter, J. Vierendeels, R. Verhoeven, and P. Troch. Numerical Simulation of Formwork Pressure While Pumping Self-Compacting Concrete Bottom-Up. Engineering Structures, Vol. 70, 2014, pp Ozyildirim, C. Virginia Department of Transportation Early Experience with Self- Consolidating Concrete. In Transportation Research Record: Journal of the Transportation Research Board, No. 1914, Transportation Research Board of the National Academies, Washington, D.C., 2005, pp Ozyildirim, C. Bulb-T Beams with Self-Consolidating Concrete on the Route 33 Bridge Over the Pamunkey River in Virginia. Publication VTRC 09-R5. Virginia Transportation Research Council, Charlottesville, Ozyildirim, C., and S. Sharp. Preparation and Testing of Drilled Shafts with Self- Consolidating Concrete. Publication VCTIR 12-R15. Virginia Center for Transportation Innovation and Research, Charlottesville, 2012.