The objective of the research presented in this thesis was to develop a concrete bridge deck topping mixture that resists the effects of differential shrinkage by decreasing shrinkage and increasing creep. . In addition, the amount of tensile creep that concrete experiences under long-term tensile stresses were quantified and compared to compressive creep values in order to gain a better understanding of how concrete behaves under tension. Test results show that the amount of tensile creep exceeded compressive creep by a factor of 2-5. Various shrinkage and creep models were compared against test data in order to quantify results and determine the best model to use for the mixes examined during this research project. Data analysis revealed that the AASHTO time dependent effects (shrinkage and creep) models outperformed the other models used in this research project. Other material property data including compressive strength, splitting tensile strength, Young's modulus of elasticity, and unrestrained shrinkage was also collected to compare against a common bridge deck topping mix to ensure that the mixes used in this research project are suitable for use in the field. A parametric study utilizing the Age Adjusted Effective Modulus (AAEM) method was performed which showed that the most important factor in reducing tensile stresses was to decrease the amount of shrinkage experienced by the concrete bridge deck topping mixture. Three concrete mixtures, one included saturated lightweight aggregates (SLWA), one including ground granulated blast furnace slag (GGBFS), and one incorporating both were tested. Preliminary results show that the inclusions of SLWA into a concrete mixture reduced shrinkage by 25% and overall tensile stress by 38%. / Master of Science

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This research evaluated the feasibility of the empirical design method for reinforced concrete bridge decks for the Florida Department of Transportation [FDOT]. There are currently three methods used for deck design: empirical method, traditional method and finite element method. This research investigated and compared the steel reinforcement ratios and the stress developed in the reinforcing steel for the three different methods of deck design. This study included analysis of 15 bridge models that met the FDOT standards. The main beams were designed and load rated using commercial software to obtain live load deflections. The bridges were checked to verify that they met the empirical method conditions based on the FDOT Structures Design Guidelines – January 2009. The reinforced concrete decks were designed using the traditional design method. Then the bridges were analyzed using three-dimensional linear finite element models with moving live loads. The reinforced concrete decks were designed using dead load moment, live load moment, and future wearing surface moment obtained from the finite element models. The required reinforcing steel ratio obtained from the finite element method was compared to the required reinforcing steel ratio obtained from traditional design method and the empirical design method. Based on the type of beams, deck thicknesses, method of analysis, and other assumptions used in this study, in most cases the required reinforcing steel obtained from the finite element design is closer to that obtained from the empirical design method than that obtained from the traditional design method. It is recommended that the reinforcing steel ratio obtained from the empirical design method be used with increased deck thicknesses to control cracking in the bridge decks interior bays.