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Founded in 1904 and headquartered in Farmington Hills, Michigan, USA, the American Concrete Institute is a leading authority and resource worldwide for the development, dissemination, and adoption of its consensus-based standards, technical resources, educational programs, and proven expertise for individuals and organizations involved in concrete design, construction, and materials, who share a commitment to pursuing the best use of concrete.
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Home > Education > Free Web Sessions
Browse from hundreds of recorded presentations from ACI Conventions and other concrete industry events.
Challenges in Determining the Deleterious Potential of Sulfide-Bearing Aggregates in Concrete
by Josée Duchesne, Laval University; Benoit Fournier, Laval University; Andreia Rodrigues, GHD; Julie Francoeur, Transport Québec; Benoit Durand, IREQ – Hydro-Québec; and Medhat Shehata, Ryerson University
Hot Topic Session: Durability of Concrete: Aggregate Matters and Alternative Test Methods (ACI Spring 2019 Convention, Québec City, QC, Canada)
Deleterious chemical reactions of aggregates in concrete are among the various mechanisms that can conduct to regular or recurring repairs or eventually the replacement of the affected elements/structures. Assessing concrete degradations in structures starts with a reliable diagnosis process performed by a concrete professional. Alkali-aggregate reaction (AAR) or any other aggregate degradation mechanism is a gradual process and determining the current condition and the potential for further damage is rather complex. Testing methods for accurate condition assessment and determination of reaction stage are limited and a deep understanding of the reactions involved and of their impact on the mechanical properties of the affected concrete are crucial in this process. Testing methods for prognosis are generally performed under accelerated laboratory conditions and their correlation with field exposure is often not very accurate. Relatively “new” reactions in concrete such as internal sulfate attack associated with sulfide-bearing aggregates need better understanding and also methods to detect reliably and accurately reactive aggregates. Therefrom, relatively new/upgraded test methods (petrographic and mechanical) for diagnosis of current level of damage due to AAR or other aggregate reactions are presented in this session. Results on the correlation between field exposed concrete blocks and laboratory results for the prevention of AAR are also presented accompanied by new information on the challenges of evaluating the deleterious potential of sulfide-bearing aggregates.
September 30 – October 6
Advanced Numerical Modeling Methodology for Strength Evaluation of Deep Bridge Bent Caps
by Serhan Guner, University of Toledo; and Anish Sharma, University of Toledo
Advanced Analysis and Testing Methods for Concrete Bridge Evaluation and Design (ACI Spring 2019 Convention, Québec City, QC, Canada) Due to the increase in traffic and transported freight in the past decades, a significant number of in-service bridges have been subjected to loads above their original design capacities. Bridge structures typically incorporate deep reinforced concrete elements, such as cap beams or bents, that have higher shear strength than slender elements. However, most in-service bridges did not account for deep beam effects in their original design due to the lack of suitable analysis methods during their design. Since the cost to rehabilitate all the overloaded bridges is prohibitive, an advanced computational analysis methodology is needed to provide a better understanding of the structural behavior and an accurate assessment of the load capacity of deep bridge bents. This study presents a state-of-the-art nonlinear analysis modeling method for the strength evaluation of reinforced concrete bridge bents while accounting for the deep beam action and advanced concrete behaviors such as tension stiffening, compression softening, and dowel action. As a case study, an existing bridge bent is examined. The effectiveness and advantages of the proposed method are discussed while comparing the calculated behavior including the load-deflection response, strength capacity, crack pattern, damage progression, and failure mode with strut-and-tie and sectional analysis methods.
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