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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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Browse from hundreds of recorded presentations from ACI Conventions and other concrete industry events.
Expanding Working Domain of Cement Based Matrices via Molecular Scale Engineered C-S-H
by Konrad Krakowiak, University of Houston
Why Nanofibers in Concrete? (ACI Fall 2020 Convention, Virtual Sessions) Coupling of organic and inorganic chemistry presents a new degree of freedom in nano-engineering of thermo-mechanical properties of cement-based materials. Despite these vast technological benefits, molecular scale cross-linking of calcium-silicate-hydrate (C-S-H) gel with organic molecules still presents a significant challenge. Herein, we report experimental results on sol-gel synthesis, structure and morphology of nanocrystalline C-S-H cross-linked with dipodal organosilanes. These novel organic-inorganic gels have layered turbostratic molecular structure with similarities to C-S-H precipitating in hydrating cement paste. The organic molecules’ chain length controls the interlayer spacing, which shows little to no shrinkage upon dehydration up to 105ºC. However, the structure gets distorted in the basal crystallite plane, in which dimer and trimer Si-polyhedra structures condense on a 2D hexagonal Ca-polyhedra layer. Cross-linked C-S-H gels display plate-like morphology with tendency toward stacking into agglomerates at the larger scale. If successfully realized in cement environment, e.g. high concentration seed, such novel organic-inorganic C-S-H gels could potentially provide cement-based matrices with unique properties unmatched by classical inorganic systems.
May 17 - 23
Investigating and Characterizing Soils for Use in Local Road Concrete Pavement Design
by Brian M. Killingsworth, National Ready Mixed Concrete Association
Design and Construction of Concrete Streets and Local Roads (ACI Fall 2019 Convention, Cincinnati, OH) While long-term concrete pavement performance is known to be somewhat insensitive to foundational soil or base strength, understanding the characteristics of the foundation is still a critical function in the design process. Many designers are unsure about what may be needed in the geotechnical investigation, how to interpret the results from the investigation, and/or how it may affect or influence the selection of the most functional pavement cross section. With these issues in mind, this session will cover what should be included in the geotechnical investigation, which laboratory tests are necessary and how the results affect the design, and how other field and lab results may be interpreted so that specifications and details are properly developed.
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