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International Concrete Abstracts Portal

Showing 1-5 of 228 Abstracts search results

Document: 

20-488

Date: 

September 1, 2021

Author(s):

Bradley S. Hansen, Ashley S. Carey, and Isaac L. Howard

Publication:

Materials Journal

Volume:

118

Issue:

5

Abstract:

Aggregate mineralogy and shape effects on concrete mechanical property relationships were evaluated using 114 concrete mixtures that used rounded gravel, crushed gravel, and limestone. Mineralogy (that is, chert versus calcium carbonate) and shape (that is, crushed versus rounded) were found to have a meaningful effect on the relationships between compressive strength (fc), elastic modulus (E), and splitting tensile strength (St). These data sets were used to benchmark several empirical relationships found in the literature to determine their ability to predict E and St based on fc. Most equations from the literature were conservative and did not consider aggregate type. A set of equations, following the form of ACI 318 and a power equation, are recommended by the authors for limestone, crushed gravel, and rounded gravel to realistically predict E and St based on fc.

DOI:

10.14359/51732933


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: 

20-265

Date: 

May 1, 2021

Author(s):

Robbie M. Damiani, Paramita Mondal, and David A. Lange

Publication:

Materials Journal

Volume:

118

Issue:

3

Abstract:

Within the last decade, interest in using waste rubber in concrete has been increasing due to sustainability concerns. However, previous work has shown a surface mismatch between rubber and paste, leading to diminished performance. The objective of this work is to determine the efficacy of shrinkage-reducing admixture (SRA) on the performance of rubberized cement samples; beyond reducing shrinkage, the use of SRA is believed to improve the adhesive bond at the interface. From initial testing, another effect was observed: adsorption of SRA on the rubber surface. Various mechanical tests and characterization techniques were implemented to understand the efficacy of these modifications. Results concluded that SRA implementation within the bulk mixture or as a pre-treatment lowered rubber contact angle, which subsequently improved compressive and pullout strength, as well as damping ratio of rubberized cement samples. By pretreating rubber, limitations associated with using SRA in the mixture design may be bypassed.

DOI:

10.14359/51730424


Document: 

20-130

Date: 

March 1, 2021

Author(s):

Kai Wu, Jianan Xu, Feng Chen, Chuyang Chen, and Zhigang Chai

Publication:

Materials Journal

Volume:

118

Issue:

2

Abstract:

The reinforcing bar cages in concrete-encased steel (CES) structures are replaced with steel fibers to form the steel fiber-reinforced concrete-encased steel (SFRCES) structures, which can avoid common difficulties in the construction of a traditional CES structure. To study the bonding properties and interfacial damage between shaped steel and steel fiber-reinforced concrete (SFRC), the pushout tests of 16 specimens were conducted. Main parameters including steel fiber ratio (ρsf) (0, 1, 2, and 3%), thickness of concrete cover (Css), and effective bonding length (Le) of specimens were considered. In this paper, some important performance indicators are obtained, such as P-S curves, bonding strength, interfacial energy dissipation, and interfacial damage variables. The experimental results show that the P-S curves at the loading end and free end have the greatest difference under the peak load. A higher ρsf has a stronger constraint effect on concrete cracks, which leads to better post-peak bonding behavior. A bigger Css can delay the interfacial damage in the middle and late stages of the test. A larger Le means more elastic deformation energy can be stored at the interface, so the damage variable increases at a slower pace.

DOI:

10.14359/51730413


Document: 

20-080

Date: 

January 1, 2021

Author(s):

Ângela Costa Piccinini, Luiz Carlos Pinto da Silva Filho, and Américo Campos Filho

Publication:

Materials Journal

Volume:

118

Issue:

1

Abstract:

This research evaluated the bond behavior of reinforcement and the mechanical characteristics in a reactive powder concrete (RPC) replacing 35% cement with blast-furnace slag. Pullout tests were performed at the ages of 3, 7, 28, 56, 63, and 91 days on cylindrical samples. The embedded length used was double the diameter of the bar. At 3 days it presented compressive strength of 41% of the maximum obtained, which was 123.06 MPa at 91 days. There was an increase in strength until the age of 56 days and after stabilization of the curves. In pullout tests, it was noticed the considerable influence of the rib, because in tests with plain bars, the bond force was below 20% of the results with ribbed bar, which reached 54.38 MPa of strength. The compression curve was similar to the bond curve. Underestimated values were observed when the researchers’ equations were applied to calculate the maximum bond strength.

DOI:

10.14359/51725995


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