This paper proposes that Unmanned Aerial System (UAS) technologies integrated with image visibility enhancement algorithms and machine learning are an efficient yet supplementary concrete bridge inspection tool. Two different image enhancement algorithms, i.e., denoise algorithm and image property adjustment, were considered in this study. To assess the adequacy of the proposed UAS technologies in the bridge inspections, the technologies were applied to identify and quantify defects on an existing concrete double-tee bridge located in the state of South Dakota using a Matrice 210 unit. During the inspections, Matrice 210 recorded videos to extract numerous UAS inspection images throughout the bridge. Machine learning was applied to categorize each of the UAS inspection images into certain defect types such as rust and spalling. The denoise algorithm was used to reduce the noise on the categorized defect images based on the pretrained denoising neural network, while the image property adjustment algorithm was employed to improve the visibility of the images by filtering the images’ brightness, contrast, and sharpness. Through these algorithms, defects on the filtered images initially presented with low visibility, were detected. Furthermore, quantification of the defects was able to be completed using pixel-based image analysis with the filtered images. From the UAS-assisted inspections, concrete spalling and rust on railings of the bridge were observed, detected, and quantified successfully. The quantification of spalling showed only a 6.00% difference compared against the inspection report data provided by the South Dakota Department of Transportation (SDDOT).

Ultra-high performance concrete (UHPC) is a novel material which shows impressive properties including high strength, increased toughness and excellent durability. One of the potential applications of UHPC is in heavily-loaded beams and bridge girders where their use can allow for more efficient design sections and increased durability. On the other hand, the high bond capacity of UHPC can eventually lead to brittle bar fracture failures in flexural members, especially when combined with low or moderate amounts of ordinary steel reinforcement (ρ ≤ 1%). This paper examines the influence of reinforcement grade on the flexural behaviour of UHPC beams. As part of the study, a series of UHPC beams built with either Grade 400 MPa ordinary steel reinforcement, Grade 690 MPa high-strength reinforcement or Grade 520 MPa stainless steel reinforcement are tested under four-point bending. The main parameters investigated include the influence of UHPC, steel type and tension steel ratio. Overall the results show that the ductility of the UHPC beams is influenced by both the tension steel ratio and steel grade/type. The results also show the benefits of combining UHPC with higher grade or higher ductility steel reinforcement.

Major bridges are requiring extended service lives of 100 years or more. This requires the use of high performance concretes and often enhanced corrosion protection provided by improved corrosion resistance of the reinforcing bars by using alloying, coatings, and/or corrosion inhibitors. Producing the entire bridge deck out of high performance concrete can lead to excessive cracking due to autogenous and drying shrinkage. Though this can be reduced by using shrinkage reducing admixtures or lightweight fines, the cost to implement these techniques for a full deck is high. However, a high performance concrete overlay uses considerably less high performance concrete, and as such can reduce the overall cost of the bridge deck and potentially allow for use of a more user friendly, less costly base concrete. This paper models the service life of a bridge deck using a high performance overlay. A probabilistic approach is used and the effect of cracking is included.

Durability is one of the most important requirements for built-environments. Federal, state, and local agencies expend significant effort to maintain the quality and condition of aging civil infrastructure, especially in aggressive service environments. Among many factors, durability influences the service life, integrity, and reliability of concrete materials and structures. Extensive research has been conducted to understand the deterioration mechanisms of concrete in an effort to extend the longevity of concrete members. This Special Publication (SP) contains nine papers selected from three technical sessions held during the virtual ACI Fall Convention in October 2021. Emphasis is placed on durable reinforcing schemes, service life prediction, structural integrity, repair and retrofit, corrosion mitigation, inspection techniques, and the application of state-of-the-art construction materials. All manuscripts were reviewed by at least two experts in accordance with the ACI publication policy. The Editors wish to thank all contributing authors and anonymous reviewers for their rigorous efforts. The Editors also gratefully acknowledge Ms. Barbara Coleman at ACI for her knowledgeable guidance.

Fiber Reinforced (FR) composites have become increasingly popular as retrofit solutions for buildings and infrastructure due to their ease of application, lightweight properties, and corrosion resistance. However, there are still research needs in this area that hinder wider adoption of fiber reinforced polymers (FRP) retrofit solutions and limit the understanding of initial and long-term performance of FRP-retrofitted components and structures. This paper presents the findings of an extensive literature review conducted by the authors to identify the state-of-the-art of FR composites, FRP-retrofitted structures and infrastructure, and guidelines and standards that address the testing, evaluation, and design of these systems. Research needs for FRP composites identified during a National Institute of Standards and Technology (NIST) workshop that convened a group of experts in industry, academia, and manufacturing are discussed. An overview of those research needs that received the highest ranking in this workshop are presented in this paper. Implementation of these ranked research needs by the FR composite research community, including NIST, will serve to impact and advance the field of FRP retrofit of buildings and infrastructure.