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Topics In Concrete
Home > Publications > International Concrete Abstracts Portal
Showing 1-5 of 65 Abstracts search results
Document:
24-095
Date:
January 1, 2025
Author(s):
Mshtaq Ahmed, Abdulrahman Alhozaimy, Abdulaziz Al-Negheimish, and Raja Rizwan Hussain
Publication:
Materials Journal
Volume:
122
Issue:
1
Abstract:
Chloride threshold values for steel reinforcing bars in reinforced concrete under the effect of varying temperatures and extended long-term conditions in hot climate are investigated. This investigation covers a gap in the current codes, including ACI 318, where the effect of temperature on the chloride threshold is not addressed. A total of 96 concrete specimens reinforced with carbon steel reinforcing bars sourced from two manufacturers were cast with different chloride contents and exposed to four temperatures of 20, 35, 50, and 65°C (68, 95, 122, and 149°F) for a period of more than 2 years. The chloride threshold values were determined based on corrosion potential, corrosion rate, and mass loss at the end of the exposure period. The results of the three techniques showed a consistent trend of significant dependency of the chloride threshold value on temperature. The average water-soluble chloride threshold values based on mass loss were found to be 0.77%, 0.72%, 0.47%, and 0.12% by weight of cement for temperatures of 20, 35, 50, and 65°C (68, 95, 122, and 149°F), respectively. These findings are significant as they showed a dramatic drop in the chloride threshold values at high temperature. This research highlights the need for reassessment of ACI Code limits considering hot climate.
DOI:
10.14359/51744379
23-359
December 17, 2024
Aaron Nzambi, Dênio Oliveira, João Filho
Structural Journal
This experimental study investigates the influence of flexural cracks and punching shear failure inclination on double-headed studs anchorage within the critical perimeter. The research also explored the technical feasibility of using synthetic coarse aggregates from bauxite residue as a sustainable alternative in structural concrete production. The results showed that the overall structural integrity is impaired at 40 to 50% due to flexural cracks at the critical perimeter of 2‧d (30°), however, the perimeter of 1.2‧d (45°) enhanced the shear reinforcement activation and shear strength up 15%, providing a balanced failure within the strengthening zone. Thus, an internal equilibrium of the concrete capacity design (IECCD) method was proposed to calculate the contribution of double-headed studs and accurate the codes of punching shear strength predictions in serviceability and ultimate limits states. In addition, synthetic aggregates performed similarly to natural aggregates, offering environmental benefits such as reducing the carbon footprint and production stages.
10.14359/51745467
22-124
September 1, 2023
Arindam Dey, Tara L. Cavalline, Miras Mamirov, and Jiong Hu
120
5
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.
10.14359/51738890
22-319
July 1, 2023
Fayez Moutassem and Samir E. Chidiac
4
A requirement for achieving sustainable concrete structures is to develop a quantitative method for designing concrete mixtures that yields the target rheological properties and compressive strength. Toward this objective, this paper proposes a mathematical model approach to improve the sustainability of the concrete industry. A postulation that packing density, a function of the concrete mixture, provides the link between concrete mixture, rheological properties, and compressive strength was investigated. Rheological models for yield stress and plastic viscosity, and a compressive strength model were adopted with packing density as a central variable. The rheological models employ a cell description that is representative of fresh concrete. The compressive strength model is based on excess paste theory to account for the concrete mixture proportions, gradation of aggregate particles, and porosity. An experimental program was developed to calibrate and test these models. Results revealed that packing density provides a consistent and reliable link, and that the concrete mixture composition can be designed to achieve the target rheological properties and hardened properties and ensure quality control. Consequently, a new mixture proportioning methodology was developed and proposed as an improvement to the ACI 211.1 mixture design method. Furthermore, a case study was conducted to test for the applicability and adequacy of this proposed method. This research outcome, which provides a quantitative approach to design concrete mixtures to meet specific strength requirements and rheology, can also be used to ensure quality control before concrete is cast.
10.14359/51738818
21-468
May 1, 2023
Damian Mateo Villa, Jennifer S. Patino, Daniel E. Mogrovejo, and Janneth G. Bernal
3
Polystyrene represents a substantial problem for the environment, as it is not properly recycled. Hence, this work seeks to demonstrate that concrete in which recycled expanded polystyrene (EPS) replaces a portion of the fine aggregate maintains adequate physical and mechanical characteristics while improving its economic and environmental sustainability. This fact is proven by evaluating concrete samples from standardized tests to determine their characteristics, as well as by implementing life-cycle assessment (LCA) and life-cycle cost analysis (LCCA). Results show that with a replacement of a 100% bulk ratio of EPS instead of fine aggregate, concrete workability, density, and compressive strength decrease up to 50% ( 2648 N/cm2 [3840 psi] concrete), 15% (2942 N/cm2 [4267 psi] concrete), and 29% (2354 N/cm2 [3414 psi] concrete), respectively, with regard to conventional concrete properties. In addition, EPS generates up to 4.2% of abrasive wear on its surface, according to 2648 N/cm2 (3840 psi) concrete with a replacement of 100% of EPS. Otherwise, a good decrease in temperature transfer up to 7°C (12.6°F) is reached in 2354 N/cm2 (3414 psi) concrete with a replacement of 100% of EPS. Furthermore, it reduces 15% of CO2 emissions and saves 16% in energy consumption with a minimal 7% increase in costs based on 2942 N/cm2 (4267 psi) concrete with a replacement of 88.2% of EPS. Finally, using a multi-criteria analysis, the optimum percentage of EPS in a 2648 N/cm2 (3840 psi) concrete is as high as 87%.
10.14359/51738666
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