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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 53 Abstracts search results
July 1, 2020
Mahdi Valipour and Kamal H. Khayat
Ultra-high-performance concrete (UHPC) can be vulnerable to variations in materials properties and environmental conditions. In this paper, the sensitivity of UHPC to changes in mixing, casting, curing, and testing temperatures ranging between 10 and 30 ± 2°C (50 and 86 ± 3.5°F) was investigated. The investigated rheological properties, mechanical properties, and shrinkage of UHPC are shown to be significantly affected by temperature changes. UHPC made with either binary or ternary binder containing fly ash (FA) or slag cement exhibited greater robustness than mixtures prepared with 25% silica fume. UHPC made with 60% FA necessitated the lowest high-range water-reducing admixture demand. With temperature increase, the yield stress of UHPC mixtures increased by up to 55%, and plastic viscosity decreased by up to 45%. This resulted in accelerating initial and final setting times by up to 4.5 and 5 hours, respectively. The increase of temperature from 10 to 30 ± 2°C (50 ± to 86 ± 3.5°F) led to a 10 to 75% increase in compressive, splitting tensile, and flexural strengths and modulus of elasticity and 15 to 60% increase in autogenous shrinkage.
Jedadiah F. Burroughs, Charles A. Weiss Jr., John E. Haddock, and W. Jason Weiss
This study presents the application of an analytical model to describe the rheological behavior of cement pastes containing silica fume at replacement rates of up to 30% by mass. The analytical model hypothesizes how water interacts with particles in a cementitious system. The coating thickness of water surrounding each particle in the system is estimated. This coating thickness is shown to correlate strongly with measured rheological properties
when fit to the Herschel-Bulkley model. To calculate coating thickness, it is necessary to account for the water absorbed by nonhydraulic components in the system, whether aggregate, supplementary cementitious materials, or mineral. The results suggest that silica fume particles may be absorptive, and this absorption capacity, although small, must be considered when designing water-starved cementitious materials. The experimental investigation involved the rheological testing of three water-binder ratios (0.20, 0.30, 0.45), three silica fume replacement levels (10%, 20%, 30%), and eight different silica fume products.
May 1, 2020
Hadi Bahmani, Davood Mostofinejad, and Sayyed Ali Dadvar
This study investigated the effects of different synthetic and mineral fibers and limestone powder on the mechanical properties of ultra-high-performance fiber-reinforced concrete (UHPFRC). For the purpose of this study, 16 mixture designs and 204 prism specimens were prepared and cured under either of wet or autoclave conditions. Measurements revealed that mixtures containing synthetic fibers recorded considerable compressive and flexural strengths close to the steel fiber-reinforced mixtures. Specimens reinforced with nylon fibers as the best fibers in this study exhibited a much better flexural performance in terms of flexural strength, deflection capacity, and post-peak ductility than did those containing ceramic and polyester fibers. Finally, specimens containing limestone powder recorded acceptable flexural strength, which was close to those only containing silica fume. The X-ray diffraction (XRD) test showed that limestone powder increased ettringite content due to the dilution effect at 180 days as the main reason for decreasing of compressive strength of mixtures.
Ashley S. Carey, Isaac L. Howard, Alta Knizley, and Jay Shannon
In this paper, a numerical model for radial-direction conduction through ultra-high-performance concrete (UHPC) cylinders was developed and experimentally validated. The focus of this research is ultimately to improve understanding of UHPC’s thermal behavior, with this portion focused on determining a convection heat-transfer coefficient for appropriate boundary condition modeling. Although constant heat-transfer coefficients are commonly assumed in literature, this paper shows that many commonly assumed constant coefficients overestimate convection performance for natural convection boundary condition environments. For well-studied geometries, numerical solutions including a temperature and time-dependent convection coefficient produced errors under 1%, whereas constant heat-transfer coefficient assumptions produced errors up to 10%. However, for less-common geometries, numerical model errors ranged from 2 to 5%.
March 1, 2020
Kacie C. D’ Alessandro, Carin L. Roberts-Wollmann, and Thomas E. Cousins
Ultra-high-performance concrete (UHPC) is known for its high
strength and advanced durability. Due to the unique formulation of this material, including a fine cementitious matrix and distributed steel fibers, UHPC displays different material behavior than conventional concrete. This paper examines the biaxial tension-compression behavior of UHPC using a novel biaxial test method and compares results to biaxial failure criterion of conventional concrete. A total of 62 specimens were tested to evaluate the effects of curing regimes and fiber orientations. While the compressive strength of UHPC increased significantly when steam treated, tensile strength did not increase to the same degree. Controlled fiber orientation provided more compressive stress resistance than random fiber orientation with the presence of increasing tensile stress. Comparing UHPC results to biaxial failure criterion recognized for conventional concrete, the Mohr-Coulomb biaxial failure criterion was shown to be a conservative model for UHPC for all fiber orientations and curing regimes.
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