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Home > Publications > International Concrete Abstracts Portal
Showing 1-5 of 458 Abstracts search results
Document:
SP364_4
Date:
December 1, 2024
Author(s):
Mohammad T. Nikoukalam, Shahabeddin Torabian, and Said Bolourchi
Publication:
Symposium Papers
Volume:
364
Abstract:
This research examines the hole-drilling method per ASTM E837, known for its minimal invasiveness, for measuring in situ stress in reinforcing bars embedded within concrete structures. The primary objective is to ascertain the applicability of this method in estimating non-apparent stresses, such as those resulting from the external loads, creep, shrinkage, or alkali-silica reaction, that are needed for structural assessment. Systematic experiments on reinforced concrete beams are conducted to validate the method’s viability in identifying these critical in situ stresses. The findings highlight the potential of the hole-drilling method to enhance structural health monitoring practices, offering an accurate tool for assessing stress states crucial for the maintenance and safety of concrete structures. The results demonstrated that while the hole-drilling method is robust for moderate-stress evaluations (up to about 70% of the nominal yield stress), it overestimates the stress in the reinforcing bar under high-stress conditions near the 100% nominal yield stress. This study contributes to the field by confirming the limits and applicability of the ASTM E837 standard for estimating the existing stress in the embedded reinforcing bars.
DOI:
10.14359/51745456
SP-362_04
June 5, 2024
Imane Bekrine, Benoît Hilloulin, Ahmed Loukili
362
Recently, considerable attention has been given to the use of calcined clays in cementitious systems due to their availability and the enhancement of concrete durability properties they can generate thanks to the pozzolanic reaction. However, the interpretation of the macro-mechanical behavior of cementitious materials incorporating calcined clays is still challenging, especially when combined with other supplementary cementitious materials, and an investigation at the microscale is required. To this end, micro and nanoindentation are local mechanical techniques that can be used to assess the micromechanical properties of these heterogeneous and complex systems. In this study, three ternary systems with 30%, 45%, and 60% substitution of cement with calcined clay and slag are compared to a CEM I-based reference mix at 28 days, in terms of mechanical performance, pore structure, and micromechanical properties. Results show that compressive strength is higher/equivalent to reference mix up to 45% of cement replacement. In addition, the elastic modulus of the pastes assessed by micro indentation was found to decrease with the substitution ratio, while the creep resistance was enhanced. Finally, mercury porosity and nanoindentation analysis showed that the higher the replacement ratio, the higher the amount of CSH in the tested ternary cement blends.
Recently, considerable attention has been given to the use of calcined clays in cementitious systems due to their availability and the enhancement of concrete durability properties they can generate thanks to the pozzolanic reaction. However, the interpretation of the macro-mechanical behavior of cementitious materials incorporating calcined clays is still challenging, especially when combined with other supplementary cementitious materials, and an investigation at the microscale is required. To this end, micro and nanoindentation are local mechanical techniques that can be used to assess the micromechanical properties of these heterogeneous and complex systems.
In this study, three ternary systems with 30%, 45%, and 60% substitution of cement with calcined clay and slag are compared to a CEM I-based reference mix at 28 days, in terms of mechanical performance, pore structure, and micromechanical properties. Results show that compressive strength is higher/equivalent to reference mix up to 45% of cement replacement. In addition, the elastic modulus of the pastes assessed by micro indentation was found to decrease with the substitution ratio, while the creep resistance was enhanced. Finally, mercury porosity and nanoindentation analysis showed that the higher the replacement ratio, the higher the amount of CSH in the tested ternary cement blends.
10.14359/51740874
CI4510Sicaras
September 29, 2023
Sicaras, V.K.
Concrete International
45
Issue:
10
Every year, ACI Foundation’s Concrete Research Council hosts a request for proposals (RFP) program that awards funding to several concrete research projects. The article describes one of these projects that focused on developing a time-dependent design model capturing the complex reality of how creep and shrinkage phenomena are interconnected.
SP357_05
April 1, 2023
Simone Ravasini, Francesca Vecchi, Beatrice Belletti, and Nicolo Bonati
357
During an extreme event occurring on a reinforced concrete structure, characterized by the loss of a load-bearing element, the remaining resisting members may develop alternate load paths to resist gravity loads. However, it is recognized that reinforced concrete flat slabs are prone to punching shear failure. This issue is particularly relevant for existing reinforced concrete structures where creep, shrinkage, and corrosion effects due to environmental conditions play a fundamental role before the occurrence of the extreme event. In this paper, nonlinear pushdown and dynamic analyses were performed on an existing continuous reinforced concrete flat slab to investigate the structural response in the case of an interior column loss. Firstly, the flexural and membrane action resisting contributions were in-deeply analyzed. Secondly, the crucial effects of creep, shrinkage and corrosion on the dynamic response and punching shear resistance of the system were critically evaluated. Finally, useful insights for the structural robustness assessment of existing RC structures subjected to material deterioration were provided.
10.14359/51738761
CI4408Attiogbe
August 1, 2022
Emmanuel K. Attiogbe
44
8
Restrained shrinkage cracking caused by differential drying is a major factor in determining the long-term durability of concrete. The article provides a procedure to evaluate the potential for restrained shrinkage cracking as a basis for prequalification of concrete mixtures. The procedure involves simple calculations and using concrete properties obtained from standard tests.
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