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International Concrete Abstracts Portal

Showing 1-5 of 410 Abstracts search results

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: 

20-253

Date: 

March 1, 2021

Author(s):

Goran Adil, Ceki Halmen, George Seegebrecht, and John T. Kevern

Publication:

Materials Journal

Volume:

118

Issue:

2

Abstract:

Corrosion performance of reinforced pervious concrete was evaluated through field and laboratory evaluations. Two reinforced pervious cemetery walls in Chicago, IL, were visually evaluated, and samples were investigated through petrographic examination. Corrosion performance of two-layered concrete samples, with an outer layer of conventional concrete and an inner layer of pervious concrete, was evaluated in the laboratory. Results indicated that pervious concrete around the reinforcement can significantly delay the cracking and spalling of samples compared to conventional concrete. Chloride profiles of samples and instantaneous corrosion rate measurements showed that corrosion of reinforcement embedded in two-layered samples was similar to conventional concrete although two-layered samples provided a longer time to cracking. Laboratory results are in agreement with long service life performance observed in the field and with prior pervious concrete corrosion studies.

DOI:

10.14359/51730514


Document: 

20-049

Date: 

January 1, 2021

Author(s):

J. Abellán-García, J. A. Fernández-Gómez, N. Torres-Castellanos, and A. M. Núñez-López

Publication:

Materials Journal

Volume:

118

Issue:

1

Abstract:

This paper investigates the tensile behavior of green ultra-high-performance fiber-reinforced concrete (UHPFRC) using commercially available steel fibers. An ecofriendly ultra-high-performance concrete (UHPC) with a low carbon footprint was developed, aiming for a compressive strength of 150 MPa (22 ksi) and a high packing density (0.81) while using recycled glass powder and micro-limestone powder as partial substitution of silica fume and ordinary portland cement. Besides the commercially available normal-strength deformed steel fibers, high-strength smooth steel fibers were used to establish a comparison. The study showed that, with appropriate hooked normal-strength and smooth high-strength steel fibers, 1% of fiber is enough to achieve strain hardening behavior. Moreover, the smooth fibers achieved the maximum tensile strength (σpc = 11.04 MPa) when 2% of volume was used. However, despite having less tensile strength, only the hooked-end fibers achieved a maximum post-cracking strain (εpc) of over 0.3% using 2% of volume.

DOI:

10.14359/51725992


Document: 

20-037

Date: 

November 1, 2020

Author(s):

Mengesha Beyene, Jose Munoz, Richard Meininger, and Anant Shastry

Publication:

Materials Journal

Volume:

117

Issue:

6

Abstract:

The reference Pittsburg Ontario alkali carbonate-reactive (ACR) aggregate source was characterized using a holistic approach to identify and quantify mineral phases, particularly reactive forms of silica and expansive types of clays in the aggregate which may have a role in the controversial ACR mechanism and resulting expansion and cracking of concrete. This research was performed using state-of-the-art analytical techniques and methods that included polarized light microscopy (PLM), quantitative image analysis (QIA) of backscattered electron (BSE) scanning electron microscope (SEM) images, acid-insoluble residue (AIR) tests, X-ray diffraction (XRD), X-ray fluorescence (XRF), and a chemical ratio method of identifying alkali-reactive carbonate rocks. Three types of silica phases were identified through PLM examination: upper silt-sized quartz grains both in the virgin aggregate and acid insoluble residue (AIR); cryptocrystalline silica dispersed and hidden in the fine-grained rock matrix and identified only in the AIR; and cryptocrystalline-to-microcrystalline silica occupying interstitial spaces of dolomitic limestone particles which lacked clay in their matrix. PLM findings were confirmed through QIA of the AIR. Particle size distribution of silica phases through QIA showed that silica phases in sizes of 0.5 to 2 μm (0.00002 to 0.00008 in.) occur in high abundance. QIA of AIR identified illite as the major clay mineral in the aggregate. While this clay type is not known to be expansive, microcrystalline to cryptocrystalline silica phases are potentially alkali-silica reactive (ASR) in concrete as opposed to ACR.

DOI:

10.14359/51726997


Document: 

19-435

Date: 

November 1, 2020

Author(s):

Xun Xi, Shangtong Yang, Xiaofei Hu, and Chun-Qing Li

Publication:

Materials Journal

Volume:

117

Issue:

6

Abstract:

The interfacial transition zone (ITZ) between cement mortar and aggregate significantly affects the cracking behavior of concrete. However, the fracture properties including the tensile strength and fracture energy of ITZ are hard to obtain directly from experiments. This paper develops an inverse numerical method for determining the fracture properties of ITZ based on a meso-scale fracture model and artificial neural network. Concrete is considered a multi-phase material, mainly consisting of aggregates, cement mortar, and ITZ. In the fracture model, cohesive elements are inserted in the mesh to achieve arbitrary cracking. The tensile strength and fracture energy of ITZ are the targeted variables to be inversely attained. A neural network is created and trained based on the simulated results, by which the optimized values of the targeted variables are obtained. Experimental results from RILEM tests are used to validate the numerical method.

DOI:

10.14359/51728123


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