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International Concrete Abstracts Portal

Showing 1-5 of 10 Abstracts search results

Document: 

18-514

Date: 

November 1, 2019

Author(s):

Andrés A. Torres-Acosta, Francisco Presuel-Moreno, and Carmen Andrade

Publication:

Materials Journal

Volume:

116

Issue:

6

Abstract:

The potential use of the electrical resistivity (ρ) and the saturated electrical resistivity (ρS) for the durability design of new concrete structures and the forecasting for in-service concrete structures has been increasing in the past three decades. Many investigations have proven the ease of the method and the possibility of it being a quality control/assurance tool during construction of new concrete infrastructure. Some previous investigations even consider the ρS test a feasible one to remove other, more complicated and expensive tests used in cement-based materials as durability indicators; a few of them defined correlations between ρS and the other indexes. The present investigation uses published data to determine if empirical correlations exist between ρS and rapid chloride permeability (RCP), and between ρS and the apparent chloride diffusion coefficient (DAP). A literature search was done on the three durability indexes in question (ρS, RCP, and DAP) and some empirical equations were derived. Good empirical correlations were observed for ρS versus RCP and ρS versus DAP. The latter correlation, obtained from data of different sources, supported that ρS and chloride diffusivity follows the well-defined Einstein law of diffusion with minor modifications for cement-based materials.

DOI:

10.14359/51718057


Document: 

110-M48

Date: 

September 1, 2013

Author(s):

H. Sezer Atamturktur, Christopher R. Gilligan, and Kelly A. Salyards

Publication:

Materials Journal

Volume:

110

Issue:

5

Abstract:

Rock-pocket and honeycomb defects impair overall stiffness, accelerate aging, reduce service life, and cause structural problems in hardened concrete members. Traditional methods for detecting such deficient volumes involve visual observations or localized nondestructive methods, which are labor-intensive, timeconsuming, highly sensitive to test conditions, and require knowledge of and accessibility to defect locations. The authors propose a vibration response-based nondestructive technique that combines experimental and numerical methodologies for use in identifying the location and severity of internal defects of concrete members. The experimental component entails collecting mode shape curvatures from laboratory beam specimens with size-controlled rock pocket and honeycomb defects, and the numerical component entails simulating beam vibration response through a finite element (FE) model parameterized with three defect-identifying variables indicating location (x, coordinate along the beam length) and severity of damage (a, stiffness reduction and b, mass reduction). Defects are detected by comparing the FE model predictions to experimental measurements and inferring the low number of defect- identifying variables. This method is particularly well-suited for rapid and cost-effective quality assurance for precast concrete members and for inspecting concrete members with simple geometric forms.

DOI:

10.14359/51685904


Document: 

110-M34

Date: 

July 1, 2013

Author(s):

Samuel D. Keske, Anton K. Schindler, and Robert W. Barnes

Publication:

Materials Journal

Volume:

110

Issue:

4

Abstract:

Five test methods were evaluated that assess the stability of fresh self-consolidating concrete (SCC): the visual stability index (VSI) test; column segregation test; rapid penetration test; sieve stability test; and surface settlement test. These tests were performed on nine precast, prestressed-suitable SCC mixtures each placed in four walls of varying heights, and the stability test results were compared to the results of ultrasonic pulse velocity (UPV) and pullout testing conducted on the hardened concrete walls. The surface settlement, VSI, and sieve stability test results were best correlated to the hardened concrete uniformity test results. Therefore, the surface settlement test should be used to prequalify precast, prestressed SCC mixtures prior to production, while the combined use of the VSI and sieve stability tests is recommended to determine batch acceptance during precast, prestressed concrete production.

DOI:

10.14359/51685785


Document: 

108-M54

Date: 

September 1, 2011

Author(s):

Jose Calavera, Jaime Fernandez-Gomez, German Gonzalez, Jorge Ley, and Pedro Lopez

Publication:

Materials Journal

Volume:

108

Issue:

5

Abstract:

The initial curing of concrete specimens for quality assurance is addressed in different ways in testing standards, which often specify requirements that are difficult to meet in practice unless very costly initial curing chambers are available. The failure to meet these requirements in many areas of the world does not appear to result in adverse consequences. This study analyzed six initial curing temperature schemes, all with cycles similar to natural conditions to avoid the simplifications inherent in constant temperature curing. Three strengths of concrete and two initial curing times (24 and 72 hours) were used in this study. The findings showed that initial curing time had no effect on 28-day strength. The 28-day strength also proved to be resilient to maximum and minimum initial curing temperatures outside the limits stated in the standards considered in this study.

DOI:

10.14359/51683260


Document: 

107-M66

Date: 

November 1, 2010

Author(s):

M. Mancio, J. R. Moore, Z. Brooks, P. J. M. Monteiro, and S. D. Glaser

Publication:

Materials Journal

Volume:

107

Issue:

6

Abstract:

The water-cement ratio (w/c) is one of the most important parameters determining the quality of cement-based materials. Currently, there is no practical way to accurately determine this ratio after all the ingredients of concrete have been mixed, posing a significant quality-control problem for the construction industry. A new method has been developed to address this challenge whereby an electrical resistivity probe is immersed in fresh concrete, providing an instantaneous and accurate measure of a concrete’s w/c. Experiments were conducted on eight concrete mixtures designed according to the ACI 211.1 procedure, with varying w/c (0.30, 0.40, 0.50, and 0.60) and fly ash percentages (0 and 25%). The results demonstrate a strong direct correlation between the resistivity of fresh concrete and the w/c. Average w/c estimates based on measurements using the resistivity probe were within ±0.01 of the actual values for all mixtures tested.

DOI:

10.14359/51664045


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