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International Concrete Abstracts Portal

Showing 1-5 of 46 Abstracts search results

Document: 

18-338

Date: 

September 1, 2019

Author(s):

Karthik H. Obla

Publication:

Materials Journal

Volume:

116

Issue:

5

Abstract:

Past research showed a correlation between the measured apparent chloride diffusion coefficient determined in accordance with ASTM C1556 and the ASTM C1202 rapid indication of chloride ion penetrability test (RCPT) results. Based on that research, a combination of RCPT and strength criteria was proposed to categorize mixtures based on their resistance to chloride ion penetration. This article proposes specification criteria based on a formation factor to categorize mixtures. The efficacy of using both approaches to categorize 44 concrete mixtures prepared from different portland cements, types and dosages of supplementary cementitious materials, and w/cm is examined. It is found that either approach can be used to categorize mixtures based on their resistance to chloride ion penetration. Specimens from 10 mixtures, moist-cured for over 8 years, were tested for surface and bulk resistivity. The same specimens were immersed in chloride solutions in accordance with ASTM C1556, and chloride-ion contents at specific depths from the exposed surface were measured and compared with the later-age bulk resistivity, early-age RCPT, and estimated formation factor.

DOI:

10.14359/51716835


Document: 

18-310

Date: 

September 1, 2019

Author(s):

M. Moini, K. Sobolev, I. Flores-Vivian, S. Muzenski, L. T. Pham, S. Cramer, and M. Beyene

Publication:

Materials Journal

Volume:

116

Issue:

5

Abstract:

Durability and long-term performance of concrete exposed to deleterious ions and environmental conditions are major concerns. The rapid chloride permeability (RCP) test is commonly used in specifications in the United States to evaluate the permeability of concrete. To evaluate the critical factors that control the service life of structures, the investigation of various concrete mixtures is required. In this paper, the performance of 54 concrete mixtures containing three types of water-reducing admixtures, two types of aggregates, and two levels of cement contents are evaluated in the RCP and freezing-and-thawing tests and the air void structure of selected mixtures are analyzed. It was found that the use of supplementary cementitious materials (SCMs) significantly enhances the performance of concrete mixtures in the RCP test. In addition, mixtures containing up to 30% of Class C fly ash and 50% slag content achieved exceptional durability performance in both RCP and freezing-and-thawing (F-T) tests. The “very-low” RCP values were found for mixtures containing Class F fly ash and polycarboxylate ether (PCE) admixture.

DOI:

10.14359/51716828


Document: 

18-309

Date: 

July 1, 2019

Author(s):

X. Wirth, D. Benkeser, N. N. Nortey Yeboah, C. R. Shearer, K. E. Kurtis, and S. E. Burns

Publication:

Materials Journal

Volume:

116

Issue:

4

Abstract:

Due to changes in energy production and increased emissions regulations, fly ashes that meet specifications for concrete production are becoming increasingly limited in North America. Woody biomass ash, ash from coal that has been co-fired with small amounts of biomass, and previously geologically disposed, weathered coal fly ashes are each vast and geographically distributed potential sources which could augment the limited supply of “on-spec” or ordinary fly ash. This study characterizes a range of these alternative ash sources to assess if they fulfill the physical and chemical requirements and the strength performance index in ASTM C618. Changes to ASTM C618 that address the current fly ash production environment are recommended, including broadening the definition of fly ash to allow for reclaimed weathered ashes, co-fired ashes, and blended ashes that meet prescriptive and performance specifications.

DOI:

10.14359/51716712


Document: 

18-311

Date: 

July 1, 2019

Author(s):

Saif Al-Shmaisani, Ryan D. Kalina, Raissa Douglas Ferron, and Maria C. G. Juenger

Publication:

Materials Journal

Volume:

116

Issue:

4

Abstract:

With the availability of ASTM C618 Class F fly ash decreasing, fly ash suppliers are working to find materials to meet demand by beneficiating ashes that do not comply with specifications and reclaiming ponded or landfilled ashes. The performance of three beneficiated and two reclaimed fly ashes was evaluated in this study by testing: 1) workability of paste, mortar, and concrete; 2) pozzolanic activity using isothermal calorimetry, portlandite consumption, and compressive strength of mortar and concrete; and 3) the ability to suppress expansion due to alkali-silica reaction and sulfate attack. Mixtures containing the fly ashes were compared against control mixtures containing portland cement and either a “production” fly ash or an inert quartz filler. All the beneficiated and reclaimed fly ashes are able to perform similarly to a production Class F fly ash, with differences in performance generally linked to particle size and shape following grinding.

DOI:

10.14359/51716713


Document: 

18-231

Date: 

May 1, 2019

Author(s):

Chunyu Qiao, Mehdi Khanzadeh Moradllo, Hope Hall, M. Tyler Ley, and W. Jason Weiss

Publication:

Materials Journal

Volume:

116

Issue:

3

Abstract:

This paper studies the influence of air content on the electrical resistivity and formation factor of concrete as these measures are often used in specifications for acceptance and payment. Experimental measurements are conducted on 30 air-entrained concretes with three water-cement ratios (w/c = 0.40, 0.45, and 0.50) over a large range of air contents (2.5 to 9.0%). The porosity of the concrete is measured, which is comparable to the theoretical estimation from the Powers-Brownyard model. Electrical resistivity measurements are performed on saturated concrete samples, and samples submerged in simulated pore solutions. The samples submerged in a bucket of simulated pore solution achieve a degree of saturation that relates to the filling of matrix pores, (that is, the Nick Point). The degree of saturation at the Nick Point (SNK) decreases as the air content increases. A formation factor (FSAT) is calculated for the saturated concrete, as well as the apparent formation factor FNK for the samples submerged which reach Nick Point saturation (SNK) in the simulated pore solution. As the air content increases, FSAT decreases due to the increased porosity (air voids) that are filled with conductive fluid, while FNK is independent on the air content (as the air voids are filled with nonconductive air). As the w/c increases, both FSAT and FNK decrease due to the increased porosity and connectivity. For the concrete with the same w/c, the addition of a high-range water-reducing admixture (HRWRA) results in higher values of FSAT and FNK due to the refined microstructure in mixtures containing HRWRA. A saturation function is used to provide a powerful tool in quality control to back-calculate FSAT that relates to different transport properties.

DOI:

10.14359/51714506


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