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

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.

Composite concrete bridges are widely used because they combine the advantages of precast concrete with those of cast-in-place concrete. However, because of the difference in shrinkage properties between the girder and the deck and because of the sequence of construction, the deck is subject to differential shrinkage tensile stresses. These tensile stresses may lead to excessive cracking. This paper demonstrates how the likelihood of deck cracking due to differential shrinkage can be reduced and how consequently the resistance of composite concrete bridges against time dependent effects can be enhanced by choosing a deck mix with low shrinkage and high creep. An experimental study on the long term properties of seven deck mixes is presented to identify a deck mix with the aforementioned properties. A comparison of three composite concrete bridge systems used for short-to-medium-span bridges is performed to identify the bridge system that is most resistant against time dependent effects. The mix with saturated lightweight fine aggregates appears to best alleviate tensile stresses due to differential shrinkage and the bridge system with precast inverted T-beams and tapered webs appears to be the most resistant.

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.

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.