Chapter 4 Chapter 5 Chapter 11 Chapter 11 Chapter 12 Chapter 12 Chapter 13 Chapter 13 Stand Alone Guide Chapter 14 Chapter 14 Chapter 15 Chapter 15 Chapter 6 Chapter 6 Chapter 7 Chapter 7 Chapter 8 Chapter 8 Chapter 9 Chapter 9 Chapter 10 Chapter 10 Chapter 1 Chapter 1 Chapter 2 Chapter 2 Chapter 3 Chapter 3 Chapter 4 Chapter 4 Chapter 5 Chapter 5

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Cracking continues to be the number one concern about bridge deck construction. Rarely is a deck without cracks constructed. Transverse cracking mainly attributable to drying shrinkage is common in bridge decks and has been observed in many bridge decks newly constructed by the Virginia Department of Transportation (DOT). Shrinkage-reducing admixtures (SRAs) in concrete reduce shrinkage and are one of the most effective ways of reducing shrinkage cracking. A low modulus of elasticity and high creep also help minimize cracking. Lightweight concrete (LWC) has a lower modulus of elasticity, higher inelastic strains, a lower coefficient of thermal expansion, a more continuous contact zone between the aggregate and the paste, and more water in the pores of aggregates for continued internal curing than normal weight concrete: all these factors help reduce cracking in LWC. Drying shrinkage can also be counteracted with the use of shrinkage-compensating concrete (SC). When properly restrained by reinforcement, SC can expand an amount equal to or slightly greater than the anticipated drying shrinkage. The research in this paper investigated the effectiveness of SC, LWC, and concrete with SRA in reducing cracks in bridge decks and to develop a low-cracking bridge deck specification for use in future Virginia DOT bridge decks. The study showed that bridges with fewer and narrower cracks could be constructed with SRA, LWC, and SC and that proper construction practices were needed to reduce bridge deck cracking. This study resulted in the Virginia DOT implementing a low-cracking bridge deck specification.

The addition of fibers to cementitious composites can provide improved ductility, energy dissipation, and resistance to cracking. However, it is also important to minimize residual deformations and provide crack-closing capabilities when the material is subjected to cyclic loading. In this study, the behavior of mortar mixtures with randomly distributed superelastic shape memory alloy fibers was investigated. Superelastic shape memory alloys are metallic alloys that possess unique characteristics such as the ability to undergo large deformations, excellent re-centering ability, and good energy dissipation capacity. To study the impact of shape memory alloys as a viable alternative to conventional fiber-reinforced cementitious composites, shape memory alloy fiber–reinforced mortar beam specimens with varying fiber volume fractions were prepared and tested under cyclic flexural loading. Digital image correlation method was used to measure full-field deformations and monitor the damage evolution on the surface of the specimens. Test results were analyzed in terms of flexural strength capacity, mid-span deflection, crack width, fiber distribution, and re-centering and crack recovery ratios for each specimen. Results indicate that the addition of shape memory alloy fibers to mortar composites can enhance flexural strength and ductility while providing re-centering and crack recovery capabilities at large deformation levels.

Bridges with adjacent box beams and voided slabs are common and have grouted shear keys to transfer the load between beams. However, cracks occur in the transverse direction and in the bond area along the joint. Even when a waterproofing membrane is in place, shear keys crack and deicing salts leak through the cracks and thus cause corrosion in the prestressing strands of the beams and deterioration of the grout. The resulting corroded and broken strands endanger the structural integrity of the bridge, and the compromised grout provides less shear transfer. In the study described in this report, two bridge structures with adjacent voided slabs were selected and three grouting materials—a nonshrink grout without any fibers, engineered cementitious composite (ECC) with polyvinyl alcohol fibers, and ultrahigh-performance concrete (UHPC) with steel fibers—were used in the shear keys. The test results and visual observations indicate that all grouting materials had good bond strengths, dictated by the strength of the existing concrete; however, ECC had the best performance, as it did not leak within the 3-month examination period and performed satisfactorily in both bridges after 1 year of observation. The bridges are overlaid with asphalt.