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International Concrete Abstracts Portal

Showing 1-5 of 334 Abstracts search results

Document: 

22-376

Date: 

December 1, 2023

Author(s):

Zachary W. Coleman and Anton K. Schindler

Publication:

Materials Journal

Volume:

120

Issue:

6

Abstract:

In this study, a procedure for interpreting impact-echo data in an automated, simple manner for detecting defects in concrete bridge decks is presented. Such a procedure is needed because it can be challenging for inexperienced impact-echo users to correctly distinguish between sound and defective concrete. This data interpretation procedure was developed considering the statistical nature of impact-echo data in a manner to allow impact-echo users of all skill levels to understand and implement the procedure. The developed method predominantly relies on conducting segmented linear regression analysis of the cumulative probabilities of an impact-echo data set to identify frequency thresholds distinguishing sound concrete from defective concrete. The accuracy of this method was validated using two case studies of five slab specimens and a full-scale bridge deck, each containing various typical defects. The developed procedure was found to be able to predict the condition of the slab specimens containing shallow delaminations without human assistance within 3.1 percentage points of the maximum attainable accuracy. It was also able to correctly predict the condition of the full-scale bridge deck containing delaminations, voids, corrosion damage, concrete deterioration, and poorly constructed concrete within 3.5 percentage points of the maximum attainable accuracy.

DOI:

10.14359/51739149


Document: 

22-124

Date: 

September 1, 2023

Author(s):

Arindam Dey, Tara L. Cavalline, Miras Mamirov, and Jiong Hu

Publication:

Materials Journal

Volume:

120

Issue:

5

Abstract:

The use of recycled concrete aggregates (RCAs) in lieu of natural aggregates improves the sustainability of the built environment. Barriers to the use of RCA include its variable composition, including the residual mortar content (RMC), chemical composition, and its potential to contain contaminants, which can negatively affect the properties of concrete or present environmental concerns. In this study, a rapid, economical method to estimate the RMC and provide the chemical characterization of RCA was developed using a portable handheld X-ray fluorescence (PHXRF) device. Models were developed using reference tests (RMC test based on the thermal shock method and chemical composition from whole-rock analysis) to correlate PHXRF results to measured values. The PHXRF shows strong potential for estimating the RMC and chemical composition of RCA. Paired with locally calibrated reference samples, the test method could be used in laboratory or field applications to characterize RCA and increase its use in bound and unbound applications.

DOI:

10.14359/51738890


Document: 

22-192

Date: 

July 1, 2023

Author(s):

Omar A. Kamel, Ahmed A. Abouhussien, Assem A. A. Hassan, and Basem H. AbdelAleem

Publication:

Materials Journal

Volume:

120

Issue:

4

Abstract:

This study investigated using acoustic emission (AE) monitoring to assess the abrasion performance of fiber-reinforced selfconsolidating concrete at cold temperatures (–20°C). In addition, the study targeted correlating the abrasion damage to AE data through AE intensity analysis parameters. Seven concrete mixtures were developed with variable water-binder ratios (w/b) (0.4 and 0.55), fiber types (steel and polypropylene synthetic fibers), fiber lengths (19 and 38 mm), and fiber volumes (0.2 and 1%). Tests on 100 mm cubic samples were conducted at –20 and 25°C, for comparison, according to the rotating-cutter technique in conjunction with AE monitoring. Characteristics of the AE signals such as signal amplitudes, number of hits, and signal strength were collected and underwent b-value and intensity analyses, resulting in three subsidiary parameters: b-value, severity (Sr), and the historic index (H(t)). A clear correlation between abrasion damage progress and AE parameters was noticed. Analyzing AE parameters along with experimental measurements generally revealed a better abrasion resistance for all mixtures when tested at –20°C compared to those at room temperature. The mixtures with steel fibers, lower w/b values, shorter fibers, and higher fiber volume showed improved abrasion resistance irrespective of temperature. Noticeably, the mixtures containing longer fibers, higher w/b values, or lower fiber dosages experienced a more pronounced enhancement ratio in the abrasion resistance when cooled down to sub-zero temperatures. Two damage classification charts were developed to infer the mass loss percentage and wear depth due to abrasion using intensity analysis parameters: Sr and H(t).

DOI:

10.14359/51738806


Document: 

22-381

Date: 

July 1, 2023

Author(s):

R. M. Ghantous, A. Evseeva, B. Dickey, S. Gupta, A. Prihar, H. S. Esmaeeli, R. Moini, and W. J. Weiss

Publication:

Materials Journal

Volume:

120

Issue:

4

Abstract:

The use of three-dimensional (3-D) printing with cementitious materials is increasing in the construction industry. Limited information exists on the freezing-and-thawing (FT) performance of the 3-D-printed elements. A few studies have used standard FT testing procedures (ASTM C666) to assess the FT response; however, ASTM C666 is insensitive to anisotropy caused by printing directionality. This paper investigates the FT response of 3-D-printed cement paste elements using thermomechanical analysis (TMA) to examine the influence of directionality in comparison to cast counterparts. Cement paste with a water-cement ratio (w/c) of 0.275 was used. The critical degree of saturation (DOSCR) as well as the coefficient of thermal expansion (COTE) were determined for specimens with varying degrees of saturation (DOS). Micro-computed tomography (micro-CT) was conducted to quantitatively understand the heterogeneities in the pore microstructure of 3-D-printed materials. For the specimens fabricated in this study, the COTE and DOSCR are independent of the 3-D-printing directionality and were comparable to conventionally cast specimens. For samples at 100% saturation, the FT damage was higher in the 3-D-printed samples as compared to the cast samples. The use of a low w/c in the 3-D-printed materials, desired from a buildability perspective, led to low capillary porosity, which thus decreased the amount of freezable pore solution and increased the FT resistance of the 3-D-printed materials. Micro-CT analysis demonstrated a significant 4.6 times higher average porosity in the interfacial regions compared to the filament cores.

DOI:

10.14359/51738808


Document: 

22-265

Date: 

May 1, 2023

Author(s):

Haikuan Wu, Chao Zhao, Zhao Zhang, Shun Kang, and Changwu Liu

Publication:

Materials Journal

Volume:

120

Issue:

3

Abstract:

In rare-earth mining projects, ammonium sulfate (AS) solution has a great impact on the concrete structure, which often causes serious damage to the structure. To improve the corrosion resistance of concrete in AS solution, recycled plastic was used to replace concrete fine aggregate. Compared with normal concrete (NC), the deterioration mechanism of recycled plastic concrete (RPC) against the corrosion of AS solution (3, 5, and 7%) was studied. Through the tests and analysis of apparent morphology, relative mass, ultrasonic wave velocity, and compressive strength—as well as scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR)—of corroded concrete, the test results indicate that many spots and corner damage occurred in the early and later stages of corroded concrete, respectively. The corrosion reaction of AS solution produced more ettringite and gypsum, resulting in serious damage. The RPC was expansive under the corrosion of AS solution, and the expansion degree was greater than that of NC. The compressive strength of RPC decreased gradually in AS solution. The corrosion deterioration mechanism of RPC was revealed by microstructure and phase analysis.

DOI:

10.14359/51738687


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