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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 475 Abstracts search results
Caitlin M. Tibbetts, Michael C. Perry, Christopher C. Ferraro, and H. R. (Trey) Hamilton
The structural design of concrete is typically based on service limit states and uses the modulus of elasticity as a design parameter. However, the modulus of elasticity of concrete used for the design of structures is typically determined indirectly using specified compressive strength. This research investigated the differences between the physical and empirically based relationships of the modulus of elasticity and compressive strength of concrete. Concrete incorporating various types of coarse aggregate was evaluated with particular emphasis on limestone from Florida formations, better known as limerock. The goal of this research was to establish the accuracy of coarse aggregate correction factors used for predicting the modulus of elasticity of concrete. It was found that a value of 1.0, rather than 0.9, was appropriate for the correction factor for Florida limerock; the current structural design guidelines used by the Florida Department of Transportation have revised the specifications to reflect this finding.
July 1, 2018
Jun Ki Lee
This study investigates the transfer length of 0.6 in. (15.4 mm) Grade 350 (2400 MPa) strand in 11.6 ksi (80 MPa) pretensioned concrete members. The test specimens were fabricated considering an accelerated construction scheme including gradual releasing and strand debonding, along with steam curing to achieve three initial concrete compressive strengths (fci′) of 5.8, 8.7, and 11.6 ksi (40, 60, and 80 MPa). At the release, the longitudinal strain profiles of both strand and concrete were measured using a series of electrical resistance strain gauges (ERSGs) to determine the transfer length. The strain profiles of the strands were in good agreement to those of the concrete and clearly presented the prestress bond transfer from the strand to the concrete. The experimental results indicate that the transfer length of high-strength concrete pretensioned members with Grade 350 strands is well-correlated to the initial compressive strength of concrete (fci′). Also, the transfer length is conservatively predicted using the design provisions in the ACI 318 and AASHTO specifications.
May 1, 2018
Jacob D. Henschen, Daniel I. Castaneda, and David A. Lange
Industry guidelines recommend that formwork be designed to withstand full hydrostatic pressures when using self-consolidating concrete (SCC) and highly flowable concrete. However, full hydrostatic pressures are seldom observed during SCC pours, meaning that it is possible to safely relax formwork design specifications. Numerous researchers have developed models that incorporate lab-tested material values to predict formwork pressure, but these models are affected by changing concrete mixture design, air temperature, humidity, and other factors that cannot be accounted for quickly. A simple field test method and model is presented in this study that predicts the formwork pressure using a calibrated behavior, which we call a “pressure decay signature.” The simple formwork pressure model is shown to agree well with experimentally measured values during the construction of two
tall-walls, suggesting that this method and model can contribute to increased cost efficiency of SCC construction while maintaining safe practices.
Yail J. Kim, Jae-Yoon Kang, Jong-Sup Park, and Woo-Tai Jung
This paper presents an analytical investigation into the performance of a reinforced concrete bridge girder strengthened with post-tensioned near-surface-mounted (NSM) carbon fiberreinforced polymer (CFRP) strips in a corrosion-overload multihazard environment. Stochastic models are formulated to examine the service- and strength-level responses, functional requirements such as deformability and vulnerability, and time-dependent reliability of the strengthened girder. In conjunction with environmental data recorded for 30 years, four service zones specified in the American Association of State Highway and Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD) Bridge Design Specifications are employed to generate practical research outcomes. Chloride-induced diffusion becomes more active in summer compared with other seasons. As such, stresses in the girders’ steel reinforcement increase with the progression of corrosion; however, the increase does not cause a fatigue concern. A marginal increase in CFRP stress is noticed, spanning a 100-year service period. The deformability of the strengthened girder is acceptable within a reduction range of up to 20%. The multi-hazard distress augments the vulnerability of the girder and, accordingly, affects the long-term reliability, which should be taken into consideration when implementing the NSM CFRP technology.
March 1, 2018
Yail J. Kim and Raymon W. Nickle
This paper presents the flexural characteristics of highway bridge girders prestressed with fiber-reinforced polymer (FRP) tendons. Of interest are the technical challenges identified by ACI Subcommittee 440-I (FRP-Prestressed Concrete): long-term multipliers, deformability, and minimum reinforcement. Aramid and carbon FRP (AFRP and CFRP, respectively) composites are used to prestress concrete girders. Based on analytical models, new design expressions are proposed for the aforementioned items, followed by an assessment using laboratory test data and full-scale benchmark bridges. The long-term multipliers calibrated per reliability theory are mostly different from the empirical multipliers adopted in ACI 440.4R-04. The girders prestressed with AFRP/CFRP sufficiently deform in flexure, even though their moment-curvature responses are not comparable with those of steel-prestressed girders. The new deformability index specifies design requirements for AFRP/CFRP-prestressed members with either compression-controlled or tensioned-controlled sections. The importance of a potential change in FRP modulus during the service life of prestressed concrete girders is examined. A factored ultimate-tocracking moment ratio of ϕMn/Mcr = 1.2 is suggested for girders prestressed with AFRP/CFRP, which aligns with the articles of existing design manuals and specifications dedicated to prestressed concrete.
January 1, 2018
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