With constrained transportation budgets there is a great need to increase the service life of bridges. Typically the deck is the weak link in the durability of a bridge with the corrosion of the reinforcing being the primary deterioration mechanism. Using Glass Fiber Reinforced Polymer (GFRP) to replace the traditional steel reinforcing eliminates reinforcing-related corrosion and should significantly increase the service life of the deck. The I-635 Bridges over State Ave in Kansas City, KS were built in the late 60’s and had an extensive history of repairs and overlays. In 2013 KDOT decided to replace the decks with traditional epoxy coated steel in the northbound bridge and GFRP reinforcing in the southbound bridge. There was a small premium to use GFRP rebar over traditional steel reinforcing which is expected to be offset by an increase in the service life of the deck. A picture of the reinforcing for the new bridge deck is shown in Figure 1.

Early-age cracking in cast-in-place reinforced concrete bridge decks is occurring more frequently now than three decades ago and principle factors that lead to early-age deck cracking are not fully understood. A finite element (FE) simulation methodology for assessing the role of shrinkage-induced strains in generating early-age bridge deck cracking is described. The simulations conducted indicate that drying shrinkage appears to be capable of causing transverse (and possibly longitudinal) bridge deck cracks as early as 9 to 11 days after bridge deck placement. The drying-shrinkage induced stresses would result in transverse cracking over interior pier supports in a typical bridge superstructure considered in the finite element simulations conducted.

A nonlinear 3D Finite Element (FE) analysis was performed to predict the post-exposure load-deflection responses of Reinforced Concrete (RC) beams strengthened in flexure using prestressed Near-Surface Mounted (NSM) Carbon Fibre Reinforced Polymer (CFRP) strips. Five RC beams (5.15 m [16.90 ft] long) were modeled including one un-strengthened control beam and four beams strengthened using NSM-CFRP strips prestressed to 0, 20, 40, and 60% of the ultimate CFRP tensile strain. The beams were severely deteriorated due to applying accelerated environmental conditions consisting of 500 freeze-thaw cycles: three cycles per day between +34°C [93°F] to -34°C [-29°F] with fresh water spray for 10 minutes at a rate of 18 L/min [4.8 gallon/min] at temperature +20°C. The accelerated environmental conditions used in this study equivalent to 0.46 year of exposure inside a chamber, corresponds to a minimum lifetime of 12.8 years in Canada. Simultaneously, each beam was subjected to a sustained load equal to 62 kN [13.9 kip] representing 47% of analytical ultimate load of the non-prestressed NSM-CFRP strengthened RC beam. The degradation which occurred in the concrete properties, concrete-epoxy interface, and steel reinforcement was considered in the FE model. Also, debonding at the concrete-epoxy interface was simulated by assigning shear and normal fracture energies and the prestressing was applied to the CFRP strip using an equivalent temperature. The FE model was validated with the experimental test results. However, the experimental and numerical load-deflection curves were comparable up to yielding but after yielding, the predicted curves were not in good agreement with the experimental ones.

When prestressed concrete (PC) bridge members such as girders and piles are exposed to chloride-laden environments, bonded prestressing strands can corrode prematurely. If corrosion is not detected timely, the strands may be damaged due to the effects of concurrent corrosion and tensile (prestressing) stresses, thus reducing the nominal strength of the member and increasing the risk of collapse. Accurate methods for detecting early corrosion in PC are needed to inform efficient decision-making for maintenance. Polarization resistance (R_p) is directly related to the charge transfer rate on the metal surface, making it a physically meaningful parameter to assess corrosion. Related measurements can be used to estimate corrosion rates in reinforced concrete, but their applicability to PC has not been studied. This paper discusses the feasibility of using R_p-based criteria for early corrosion detection in PC. Five PC pile specimens were exposed for over two years to salt water wet/dry cycles. Open-circuit potential and R_p measurements were routinely performed. After detecting sustained drops of open-circuit potential and R_p and keeping the specimens under exposure for different periods, the strands were removed and inspected to assess corrosion vis-à-vis electrochemical measurements. The results were used for the preliminary definition of open-circuit potential and R_p thresholds associated with different corrosion patterns on prestressing strands in PC structures.

In recent years concrete bridge structures in the USA have been experiencing varied levels of premature concrete deterioration due to alkali-silica reaction (ASR) and related condition delayed ettringite formation (DEF). While these deleterious reactions can affect various concrete bridge members under the right conditions, bridge columns can be notably more susceptible due to their unique exposure conditions and aggressive environments. The degree of deleterious reactions in concrete bridge columns is dependent on susceptibility of the aggregate, and on environmental factors, such as temperature, moisture, and external sources of alkalis. Temperature gradients are known to affect the rate and severity of the ASR expansion. Moisture gradients can be facilitated by high atmospheric humidity, exposure to weather, proximity to water spray from adjacent roadways, malfunctioning joint systems, and/or failed drainage systems, which collectively can provide sufficient conditions for ASR and DEF expansion. This paper suggests that a review of the aggressive environmental conditions at the bridge site can provide valuable insight into the occurrence and progression of premature concrete deterioration and provide direction as to a future course of action for maintenance and repair for concrete bridge columns. Repair procedures are provided dependent on the severity of premature concrete deterioration.