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International Concrete Abstracts Portal

Showing 1-5 of 393 Abstracts search results

Document: 

21-470

Date: 

November 2, 2022

Author(s):

Julie K. Buffenbarger, James M. Casilio, Hessam AzariJafari, and Stephen S. Szoke

Publication:

Materials Journal

Abstract:

The overdesign of concrete mixtures and substandard concrete acceptance testing practices significantly impact the concrete industry's role in sustainable construction. This study evaluates the impact of overdesign on the sustainability of concrete and embodied carbon emissions at the national and project scales. In addition, this paper reviews quality results from a concrete producer survey; established industry standards and their role in acceptance testing in the building codes; the reliance on proper acceptance testing by the Licensed Design Professional, Building Code Official, and the project owner; and the carbon footprints that result from overdesign of concrete mixtures. In 2020, a field survey conducted on over 100 projects documented Pennsylvania's quality of field testing. Of those surveyed, only 15% percent of the projects met the testing criteria within the ASTM and building code requirements. As a result, the total overdesign-induced cement consumption is as large as 6.7% of the U.S. estimated cement used in the U.S.

DOI:

10.14359/51737334


Document: 

21-360

Date: 

September 1, 2022

Author(s):

F. Dabbaghi, A. Tanhadoust, M. L. Nehdi, M. Dehestani, H. Yousefpour, and H.-T. Thai

Publication:

Materials Journal

Volume:

119

Issue:

5

Abstract:

Structural lightweight-aggregate concrete (LWAC) has gained a broad range of applications in the construction industry owing to its reduced dead load and enhanced fire resistance. In this study, the potential of using lightweight expanded clay aggregates as a partial replacement for fine and coarse natural aggregates was experimentally and numerically examined. Testing was performed on cylindrical specimens made of normalweight and lightweight concrete incorporating microsilica as a partial replacement for cement to determine the associated stress-strain behavior. Subsequently, three-point bending testing was conducted on reinforced concrete beams to evaluate their structural behavior. Four levels of temperature were considered: 25°C (ambient temperature), and 250, 500, and 750°C (elevated temperatures). The finite element method through Abaqus software was deployed to numerically investigate the behavior at elevated temperatures through a comprehensive parametric study. The experimental and numerical results indicate that under high-temperature exposure, LWAC outperforms its normal counterpart in terms of strength, stiffness, and Young’s modulus. It is also noticeable that LWAC beams retained their load-bearing capacity better than normal weight aggregate concrete (NWAC) after reaching the peak load.

DOI:

10.14359/51736093


Document: 

22-064

Date: 

August 29, 2022

Author(s):

Julia A. Bruce, Evan C. Bentz, Oh-Sung Kwon

Publication:

Materials Journal

Volume:

119

Issue:

6

Abstract:

This paper summarizes the results of a pilot experimental program intended to develop robust data for global airflow through cracked concrete, with comparisons against a traditionally used prediction method. Current models for predicting airflow through concrete based on Poiseuille flow poorly translate to large-scale specimens and real-world conditions without calibration. This paper presents a novel testing apparatus that will be used to identify key variables affecting flow rate and develop numerical prediction methods for industrial applications.

DOI:

10.14359/51737197


Document: 

22-023

Date: 

August 28, 2022

Author(s):

Saman Hedjazi and Ehsanul Kabir

Publication:

Materials Journal

Volume:

119

Issue:

6

Abstract:

Chloride diffusivity and steel corrosion are two major factors in durability characteristics of concrete structures. It is possible to use the electrical resistivity (ER) of concrete as a measure of concrete’s ability to resist the movement of ions within the material. In this study, surface electrical resistivity (SR) and bulk electrical resistivity (BR) of concrete cylinders were measured from 3 to 161 days for concrete mixes with four varying water to cement (w/c) ratios (0.45 to 0.60) and three distinct cement types. The study investigated the influence of important durability parameters such as cement type, long-term curing period, and w/c ratio on concrete electrical resistivity. In addition, the impact of cylinder size on SR of concrete was observed. The findings show that both SR and BR of concrete decrease with increasing w/c ratio except for concrete with cement Type-I/II, which showed a minor increase in resistivity with a w/c ratio of 0.55. Concrete with Type-V cement showed the highest electrical resistance. Moreover, a strong linear relationship between the two types of resistivity was established, and a new equation was introduced in terms of cement type, w/c ratio, and long-term curing period. The correlation between SR and BR was validated by determining the mean absolute error (MAE) of the proposed equation for the three types of cement, which were 0.41 (Type-I/II), 0.65 (Type-III), and 0.35 (Type-V). For all three cement types, the mean absolute percentage error (MAPE) and coefficient of variation (COV) were within acceptable limits, and the 95% confidence interval (CI) indicated a small error margin for the proposed equation when estimating BR from SR using experimental data. Statistical analysis showed that the new equation was less reliable for Type-III cement than the other two types, possibly due to its rapid strength increase property.

DOI:

10.14359/51737191


Document: 

22-074

Date: 

August 28, 2022

Author(s):

Yubo Sun, Yaxin Tao, A. V. Rahul, Guang Ye, Geert De Schutter

Publication:

Materials Journal

Volume:

119

Issue:

6

Abstract:

The rapid workability loss of alkali-activated materials (AAM) has been a major obstacle limiting its onsite application. In this study, two conventional SPs (made of polynaphthalene sulfonate (PNS) and lignosulfonate (LS) salts), which have been reported to be effective in some specific AAM mixtures were separately applied in alkali-activated slag (AAS) concretes. A comprehensive testing program was performed to study their effect on reaction kinetics, rheology evolution, and strength development. Results showed sodium silicate-activated AAS mixtures exhibited lower yield stress than those activated by sodium hydroxide. In hydroxide media, PNS and LS remained effective to reduce yield stress and increase slump value, while they both failed to improve the rheological behavior of AAS activated by silicate. Moreover, the inclusion of 2% admixtures did not result in much strength reduction in both activators although LS showed a retardation effect and subsequent increase in the setting time in the fresh state.

DOI:

10.14359/51737192


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