Editors: Yail J. Kim, Baolin Wan, Isamu Yoshitake

Since the major milestones of sustainability, such as the Hannover Principle in 1991 and the Kyoto Protocol in 1997, the concept of sustainability has been broadly adopted by various disciplines. New construction consumes considerable amounts of energy and materials, and CO2 emission in 2020 is expected to increase by 100%, compared with that of today. Technical communities are responsible for improving the sustainability of the built-environment by using more durable and highly efficient materials to reduce the need for replacement, maintenance, or repair. When subjected to aggressive environments, the performance of constructed concrete bridges and their elements is of interest from socioeconomic perspectives. Advances in a variety of aspects are required to achieve such a goal, including the durability of concrete members, performance monitoring technologies, evaluation methodologies, damage assessment, and structural rehabilitation. This Special Publication (SP) includes 10 papers selected from the three special sessions held at the ACI Fall convention in Washington, DC, October 2014. Each submitted manuscript has been rigorously reviewed and evaluated by at least two experts. The editors wish to thank all contributing authors and anonymous reviewers for their endeavors.

Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP-304

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.

This paper presents a detailed investigation into the load-deformation response of reinforced concrete beams strengthened with mechanically fastened fiber-reinforced polymers (MF-FRP). A bearing-slip model was developed for MF-FRP connections fastened with concrete expansion anchors. The model was used to predict the interfacial change in strain between the concrete and the FRP. When combined with load deformation constitutive equations, the bearing-slip model better predicted the load-deformation behavior in MF-FRP strengthened concrete beams. Comparisons to experimental data showed that the developed method reasonably predicts (typically within 8%) actual beam response at ultimate load. Moment-curvature diagrams were also developed and used to predict midspan deflection, typically within 30% of experimental results.

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.

Self-consolidating concrete (SCC), as defined by ACI 237R-07, is a very flowable, non-segregating concrete that can spread into placed, fill the formwork and encapsulate the reinforcement without any mechanical consolidation. SCC, compared to traditional concrete mixtures, has primary benefits that include a reduction in equipment and labor associated costs as well as higher construction effectiveness. Innovative materials such as high volume fly ash concrete (HVFAC), represent a substantial advantage to producing stronger, more durable cast-in-place (CIP) concrete members. A level of 50% fly ash to cement proportion, as well as both normal strength self-consolidating concrete (NS-SCC) and high strength self-consolidating concrete (HS-SCC), were employed in the implementation project for Missouri Bridge A7957. The objective of this research was to provide an implementation test bed and showcase for the use of these materials. The serviceability and structural performance, both short-term and long-term, of the concrete members within the bridge were monitored in an effort to investigate the in-situ performance of not only SCC but also HVFAC. The initial instrumentation program consisted of obtaining the temperature, strain, and deflection data for the different components within the bridge’s structure, from casting through service conditions. The results obtained from this two-year monitoring program will lead to propose certain specification requirements that can be used for future project implementations.