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International Concrete Abstracts Portal

Showing 1-5 of 860 Abstracts search results

Document: 

20-007

Date: 

May 1, 2021

Author(s):

Franco Zunino, Fernando Martirena, and Karen Scrivener

Publication:

Materials Journal

Volume:

118

Issue:

3

Abstract:

The climate emergency requires the adoption of strategies and technologies that effectively reduce CO2 emissions in the short to midterm to keep the global temperature rise below 2°C above pre-industrial levels. Concrete is the substance most consumed by humanity after water. The blended cements in which supplementary cementitious materials replace part of the energy-intensive clinker are the most realistic means to obtain large-scale CO2 reductions. Limestone calcined clay cements (LC3)—blended cements produced by the combination of limestone, calcined clays, and portland cement (OPC)—provides a solution that achieves equivalent mechanical performance to OPC, better durability against chloride, and alkali-silica reaction reduction of CO2 emissions by approximately 40%. Furthermore, it is cost-effective compared to OPC currently on the market. Due to the similarities with OPC, it is a material that can be adopted today using the same construction equipment and workforce worldwide.

DOI:

10.14359/51730422


Document: 

19-421

Date: 

May 1, 2021

Author(s):

Sary A. Malak, Neven Krstulovic-Opara, and Rawan Sarieldine

Publication:

Materials Journal

Volume:

118

Issue:

3

Abstract:

This paper presents the derivation as well as empirical verification of a compressive stress-strain model of concrete confined with fiber-reinforced concrete (FRC) jackets made using steel fibers. Both conventional (that is, strain-softening) FRC and high-performance (that is, strain-hardening) FRC (HPFRC) were considered. The model accounts for the tensile response of the jacket as a function of the fiber properties, fiber volume fraction, orientation, and the effects of fiber debonding, fiber pullout, and multiple cracking. Specific FRC and HPFRC materials used in this study include fiber-reinforced mortar (FRM), FRC, and slurry-infiltrated fiber-reinforced concrete (SIFCON), all made using steel fibers. Experimental behavior of model columns jacketed with FRC and HPFRC was compared to that of columns confined with conventional fiber-reinforced polymer (FRP) jackets. HPFRC jackets made with continuous aligned fibers exhibited fiber debonding and multiple cracking leading to the post-peak softening response. Varying the orientation of fibers in FRC and FRM jackets produces radial tensile stresses on the concrete core, thus reducing the strength of confined concrete. Concrete confined with FRC jackets exhibited post-peak softening response with lower ductilities than concrete confined with HPFRC jackets due to the random orientation and lower volume fraction of fibers within FRC jackets. HPFRC jackets with steel fibers are expected to sustain large rupture strains in the longitudinal and transverse directions, which translates into an improved ductility and energy absorption, making it a suitable retrofit option for existing columns.

DOI:

10.14359/51730419


Document: 

19-444

Date: 

May 1, 2021

Author(s):

Saman Hedjazi and Daniel Castillo

Publication:

Materials Journal

Volume:

118

Issue:

3

Abstract:

This paper determines the effect of steel, glass, and nylon fibers on the elastic modulus of concrete. The effect of different fiber volume fractions (0.1, 0.25, 0.5, 0.75, 1, and 1.5% vol.) and water-cement ratios (w/c: 0.32 to 0.6) on the elastic properties of concrete was investigated using the fundamental resonant frequencies. Experiments were carried out on more than 100 standard cylindrical specimens. The experimental values were determined using resonance frequencies and compared to the available empirical equations in the literature and those of ACI 318 and ACI 363. The dynamic elastic modulus of concrete in the longitudinal and transverse directions were determined experimentally using the resonance test gauge (RTG). Moreover, the dynamic modulus of rigidity of concrete was also determined using the RTG. The results show that the modulus of elasticity of fiber-reinforced concrete (FRC) with a coarse-to-fine aggregate ratio (C/S) less than 1 decreases with the addition of fibers. A new equation to better evaluate the elastic modulus of FRC within the range of 0.1 to 1.5% of fiber volume fraction is proposed. The proposed equation shows good agreement with experimental results.

DOI:

10.14359/51730420


Document: 

D118-M03

Date: 

May 1, 2021

Author(s):

Ki Yong Ann

Publication:

Materials Journal

Volume:

118

Issue:

3

Abstract:

Disc. 117-M59/From the May 2020 ACI Materials Journal, p. 111 Corrosion Resistance on Recycled Aggregate Concrete Incorporating Slag. Paper by Anwar Al-Yaqout, Moetaz El-Hawary, Khallad Nouh, and Pattan Bazienth Khan


Document: 

20-217

Date: 

May 1, 2021

Author(s):

R. D. Kalina, S. Al-Shmaisani, S. Seraj, R. Cano, R. D. Ferron, and M. C. G. Juenger

Publication:

Materials Journal

Volume:

118

Issue:

3

Abstract:

Fly ashes with high alkali contents have been observed to be less effective in controlling expansion due to alkali-silica reaction (ASR) in concrete than low-alkali fly ashes, a problem that can be hard to predict using accelerated testing. Many natural pozzolans have high alkali contents, and there is concern that these alkalis may likewise reduce their effectiveness in ASR control and affect accelerated test results. This study examines the performance of natural pozzolans in ASR testing. The mineralogies of the natural pozzolans were determined using Rietveld quantitative X-ray diffraction (XRD), and the compositions of the natural pozzolans were determined using X-ray fluorescence spectroscopy (XRF) and available alkali testing. The results suggest that the available alkalis from fly ashes and natural pozzolans are different, and high-alkali natural pozzolans perform well in both the accelerated mortar bar and concrete prism tests for ASR.

DOI:

10.14359/51732598


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