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International Concrete Abstracts Portal

Showing 1-5 of 56 Abstracts search results

Document: 

18-345

Date: 

July 1, 2020

Author(s):

Ashutosh G. Dabli, Abhay N. Bambole, and Kamalkishor M. Bajoria

Publication:

Materials Journal

Volume:

117

Issue:

4

Abstract:

The use of strain relief method is one of the most direct methods for determination of in-place stresses. In this method, a hole is drilled in the concrete member and the change in strain in the vicinity of the hole, on the surface of the member, is measured by means of electrical resistance strain gauges (ERSG). This change in strain due to drilling is used to assess the in-place stress in the member using constitutive relationship and calibration coefficient. This paper presents the experimental application of incremental hole drilling method (IHDM) in concrete under uniaxial stress. A small hole of 25 mm diameter and 40 mm deep was drilled incrementally to estimate the in-place stress in an axially loaded column with minimum damage. Dry drilling was used to eliminate the effect of swelling due to moisture (water) during the drilling. The experimental strain released was then correlated with an analytical solution using the theory of elasticity and finite element method (FEM). The excellent agreement of experimental results with analytical and numerical values of strain released suggests that IHDM can be conveniently used to evaluate in-place stresses in columns.

DOI:

10.14359/51724612


Document: 

19-177

Date: 

March 1, 2020

Author(s):

Piotr Wiciak, Giovanni Cascante, and Maria Anna Polak

Publication:

Materials Journal

Volume:

117

Issue:

2

Abstract:

The ultrasonic pulse velocity (UPV) method is commonly used as a nondestructive testing (NDT) method in civil engineering and is the ASTM standard for the relative evaluation of concrete quality. However, its limitations due to specimen dimensions or the frequency content of the transmitter excitation are not well understood. The only ASTM recommendation related to the specimen dimension is that the length should be larger than one wavelength. In this study, an experimental program is designed to specifically address the current gap in the understanding of transducer coupling and geometric effects on UPV testing. A state-of-the-art laser vibrometer and numerical simulations are used to evaluate a group of 30 specimens to give a comprehensive range of dimension-to-wavelength ratios. This study shows the response of the ultrasonic transducers in terms of the actual displacements, which indicate their complex character instead of the single pulse response typically assumed. In addition, to improve the reliability of the UPV test, the minimum specimen length-to-wavelength ratio should be greater than 4, instead of 1 as typically recommended, and the diameter-to-wavelength ratio should be greater than 3 instead of 1. If the new set of recommendations is not fulfilled, the error of the UPV measurements can reach up to 20%.

DOI:

10.14359/51722399


Document: 

18-565

Date: 

January 1, 2020

Author(s):

Julie Ann Hartell and Hang Zeng

Publication:

Materials Journal

Volume:

117

Issue:

1

Abstract:

Based on a 10-year climate survey for Oklahoma City, OK, three exposure regimens were devised: cyclic high temperature exposure, cyclic freezing-and-thawing exposure, and cyclic wetting-and-drying exposure. A total of four different test methods were compared to determine the extent of damage induced by the exposure mechanisms. Two standard nondestructive methods—ultrasonic pulse velocity and resonant frequency—were compared along with compression load testing. It was found that resonant frequency testing was more sensitive to microcrack formation. All methods discerned a change in properties after 30 cycles of freezing-and-thawing exposure. Interestingly, all three exposure regimens demonstrated a similar extent in degradation after 90 exposure cycles; however, high temperature and wet-dry cyclic exposure induced further damage than freezing-and-thawing-induced damage. Moreover, acoustic emission (AE) monitoring was performed during mechanical loading. A simple AE parameter-based evaluation confirmed the presence of material distress as that found for the destructive and nondestructive evaluation.

DOI:

10.14359/51719078


Document: 

18-059

Date: 

January 1, 2019

Author(s):

Eric Garcia, Ece Erdogmus, Michael Schuller, and Donald Harvey

Publication:

Materials Journal

Volume:

116

Issue:

1

Abstract:

The experimental results of a novel ultrasonic monitoring method to identify different types of flaws in reinforced concrete are presented. The authors’ previous work has demonstrated the ability to use the proposed ultrasonic guided wave leakage (UGWL) to identify the onset of mechanical delamination. This paper presents the results from using the UGWL method to identify chemical delamination (corrosion) and cracking in concrete (other than delamination at the steel-concrete interface) in reinforced concrete. The proposed UGWL method monitors the change in amplitude of ultrasonic waves leaked from a guided wave transmitted through an embedded steel reinforcing bar. The energy of UGWL is influenced by the conditions between the steel reinforcing bar, acting as the waveguide, and the surrounding concrete. This experimental study demonstrated that the UGWL monitoring method is sensitive not only to the onset of delaminations, but also to the development of corrosion activity and cracks.

DOI:

10.14359/51710962


Document: 

16-256

Date: 

November 1, 2018

Author(s):

Siwar Naji, Kamal H. Khayat, and Mourad Karray

Publication:

Materials Journal

Volume:

115

Issue:

6

Abstract:

The objective of this paper is to investigate the effect of the sensor size used in the piezoelectric ring actuator technique (P-RAT) on the accuracy of shear wave (S-wave) measurements that can be used to determine setting characteristics of concrete. Three different P-RAT sensor dimensions operating at different central frequencies of 25, 28, and 45 kHz (big, medium, and small P-RAT, respectively) were investigated. In total, 14 self-consolidating concrete (SCC) mixtures were proportioned with slump-flow values of 600 to 780 mm (23.6 to 30.7 in.). A conventional concrete was also prepared with 220 mm (8.7 in.) slump. The quality of the transmitted signal was found to be higher when using the big P-RAT sensor where less scattering and less energy loss were obtained. This can make it easier to determine the S-wave arrival time, which is needed to calculate the S-wave velocity for concrete with relatively high precision. The setting time of concrete based on the criteria of the S-wave velocity (Vs) derivative is shown to correspond well to values evaluated using the standard penetration resistance test tested on mortar sieved from concrete. The results showed that the big P-RAT sensor is suitable to determine the setting time of concrete by means of the derivative S-wave velocity (in time domain). However, the average setting time of mortar sieved from concrete determined from the standard penetration resistance occurred approximately 60 minutes later compared to the setting time of concrete obtained with the P-RAT approach. This shift can be due to the presence of coarse aggregate that can affect Vs.

DOI:

10.14359/51706939


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