| Bridge decks are deteriorating under repeated mechanical loading, shrinkage-induced stresses, thermal cycles, and environmental attack. Problems with corrosion of reinforcing steel and consequent spalling and delamination in reinforced concrete bridge decks are considerably intensified by the use of deicing salts. As a result, protective concrete overlays including latex-modified concrete (LMC) and microsilica concrete (MSC) overlays are being employed on bridge decks as part of rehabilitation and corrosion protection strategies. The overlay also provides an aesthetic product and a good riding quality. In addition to the typical advantages of the overlay; this study addresses the effect of bonded LMC and MSC overlays on the overall structural behavior of the bridge system and the advantages that can be gained from adding discontinuous synthetic and steel fibers to the LMC and MSC overlays.; This study encompassed extensive laboratory investigations and field application on a full scale prototype bridge system, 82 ft long and 18 ft wide with equal span lengths of 40 ft. As a result plain and fibrous LMC and MSC overlay mixtures were developed (plain LMC, LMC with synthetic fibers, LMC with steel fibers, plain MSC, MSC with synthetic fibers, and MSC with steel fibers) to meet target performance characteristics in terms of strength, permeability, hardened air-void system, bond strength, shrinkage, and crack arresting mechanism (toughness). Typically, the mixtures with synthetic fibers showed favorable performance over the mixtures with steel fibers due to the uniform distribution of synthetic fibers throughout the concrete, and LMC overlay mixtures showed superior performance over MSC overlay mixtures mainly in terms of permeability and shrinkage. The bond strength and the composite action between the overlay and the bridge deck were also evaluated under actual environmental exposures and full-scale low cycle fatigue load tests simulating AASHTO truck service load, overload, and ultimate load conditions. Following the laboratory and field studies, an innovative technique for casting LMC with synthetic fibers using mobile mixers is tried and proved to produce LMC with uniform distribution of the synthetic fibers and with high performance characteristics.; The shrinkage data of the studied overlay types in conjunction with other available shrinkage data for high performance concrete (HPC) were used to provide a simplified strength-based shrinkage prediction model that is applicable to both conventional and HPC. The final portion of the study included performing nonlinear finite element analysis (FEA) to study important issues for the bridge deck-overlay system related to the effect of the overlay on the stiffness of the bridge system, the live load-induced bond stresses, effect of cracking on the live load-induced bond stresses, and effect of the overlay thickness on shrinkage-induced bond stresses. The FEA were validated with the experimental results obtained from full-scale testing of the prototype bridge system. The FEA confirmed that adequately bonded concrete overlay improves the stiffness, cracking load, and the ultimate strength capacity of the bridge system. |
