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International Concrete Abstracts Portal

Showing 1-5 of 312 Abstracts search results

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: 

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: 

20-166

Date: 

March 1, 2021

Author(s):

Jiayin Tao, Rita Maria Ghantous, Ming Jin, and Jason Weiss

Publication:

Materials Journal

Volume:

118

Issue:

2

Abstract:

The objective of this study is to determine whether the addition of silica fume (SF) can accelerate a reduction in the degree of saturation (DOS) of sealed cementitious materials at early ages, thereby increasing the freezing-and-thawing (F-T) resistance of the paste. This study investigated the influence of SF on the F-T resistance of cementitious materials using two techniques. The first technique consists of quantifying the DOS of cementitious materials at early ages and compares it to the critical degree of saturation (DOSCR). The second technique consists of determining the difference in the length of the cement paste sample before and after exposure to an F-T cycle at early ages. The change in length during the F-T cycle is an indicator of the development of damage caused by F-T. The DOS decreases faster when a higher amount of SF replaces cement. Consequently, the DOS of SF cement paste samples are more likely to be below DOSCR faster than plain cement paste samples when the samples are sealed.

DOI:

10.14359/51730414


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: 

18-315

Date: 

March 1, 2021

Author(s):

John S. Lawler, Jonah C. Kurth, Stephen M. Garrett, and Paul D. Krauss

Publication:

Materials Journal

Volume:

118

Issue:

2

Abstract:

Reliability-based durability design of reinforced concrete structures requires a probabilistic service life modeling approach. Probabilistic service life modeling of chloride-induced corrosion should consider the statistical distributions of key parameters that influence corrosion initiation and subsequent damage. For typical reinforced concrete structures (such as bridge decks), these are chloride exposure, chloride penetration resistance of the concrete, chloride-induced corrosion threshold, depth of concrete cover, and corrosion propagation time. Assessing the impact of the use of corrosion-resistant reinforcement, such as epoxy-coated reinforcing bars (ECR), is typically performed through a selection of the chloride threshold and/or propagation time. This paper provides recommendations for statistical distributions for the chloride threshold to be used in service life modeling for structures containing carbon steel and ECR based on both experimental work reported in the literature and field investigations of existing structures conducted by the authors.

DOI:

10.14359/51730411


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