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International Concrete Abstracts Portal

Showing 1-5 of 30586 Abstracts search results

Document: 

21-220

Date: 

May 14, 2024

Author(s):

Brian Giltner, Seamus Freyne, Anthony Lamanna

Publication:

Materials Journal

Abstract:

The focus of the study is to determine the optimum length of micro (average diameter less than 0.3 mm) and macro (average diameter greater than or equal to 0.3 mm) hemp fibers subjected to tensile loading in a cement paste mixture. Optimizing the length of the fibers to carry tensile loading for concrete members is important to minimize the waste of hemp material and to provide the best performance. This study evaluated three water/cement (w/c) ratios; 0.66, 0.49, 0.42 (f’c= 17.2, 24.1, 27.6 MPa respectively – f’c = 2500, 3500, 4000 psi respectively). Because of the high cost of cement, the replacement of cement with fly ash was also part of the program to determine if the addition of fly ash would have a negative impact on the performance of the hemp fibers. The results show that micro and macro hemp fibers bonded to the cement matrix and carry higher tensile loads at higher w/c ratios. Statistical analysis (regression modeling) shows that the optimum length for macro hemp fibers is 30 mm (1.18 in.) and 20 mm (0.79 in.) for micro-fibers.

DOI:

10.14359/51740822


Document: 

23-280

Date: 

May 7, 2024

Author(s):

N. Prem Kumar, J. Maheswaran, M. Chellapandian

Publication:

Materials Journal

Abstract:

In this research work, efforts to develop a sustainable natural fiber-reinforced strain-hardening cementitious composite (NFSHCC) mixture are attempted. The key objective of the present study is to develop and characterize the NFSHCC mixture prepared using plant-based fibers such as pineapple, flax, kenaf, and hemp. First, the raw natural fibers were pre-treated using an alkaline NaOH solution to remove the biodegradable properties such as wax, lignin, etc. Using the treated natural fibers, the NFSHCC mixture was produced for a detailed mechanical and morphological characterization. Results reveal that flax fiber-based SHCC could develop the characteristics of artificial fiber-based SHCC, such as high tensile strength and large ultimate strain limits. Specifically, the flax SHCC specimens showed a large tensile strength and ultimate strain values of 10.3MPa (1.49 ksi) and 2.5% respectively. Moreover, the micro-structural characterization using field emission scanning electron microscope analysis (FESEM) revealed excellent matrix-fiber bonding which eventually led all NFSHCC samples to exhibit better mechanical properties on par with the commercial fibers.

DOI:

10.14359/51740783


Document: 

23-207

Date: 

May 7, 2024

Author(s):

Zhao-Dong Xu, Yi Zhang, Jin-Bao Li, and Chang-Qing Miao

Publication:

Materials Journal

Abstract:

Accurately measuring the working stress of concrete through the stress release method is a crucial foundation for assessing the operational condition of building structures and formulating maintenance and reinforcement strategies. The slotting method, employed within the stress release technique, not only addresses the limitations associated with the core drilling and hole drilling methods but also offers a practical solution for engineering detection. This paper presents a novel multi-step slotting method employing a stress release rate model as its foundation. The fundamental equations governing space-related issues are introduced, and a theoretical model of the stress release rate is derived. By employing a multi-step slotting process instead of the conventional one-step slotting approach, the limitations of the traditional drilling method are overcome. The stress release rate model is calibrated using numerical simulation outcomes, followed by both numerical simulation and experimental verification. With a relative error of 3.5% between theoretical and simulated values, and 9.4% with experimental values after excluding the initial slotting data, it is evident that the stress release rate model demonstrates notable accuracy and applicability. This reaffirms the effectiveness and convenience of the multi-step slotting method for measuring concrete working stress.

DOI:

10.14359/51740782


Document: 

23-172

Date: 

May 1, 2024

Author(s):

Ju-Hyung Kim, Yail J. Kim, and Hong-Gun Park

Publication:

Structural Journal

Volume:

121

Issue:

3

Abstract:

This paper presents mechanics-based modeling approaches to understand the shear behavior of squat walls reinforced with glass fiber-reinforced polymer (GFRP) bars when subjected to lateral loading. The applicability of design provisions in published specifications is examined using collated laboratory test data, resulting in the need for developing revised guidelines. Analytical studies are undertaken to evaluate the effects of reinforcement type on the response of load-bearing walls and to establish failure criteria as a function of various stress states in constituents. Obvious distinctions are noticed in the behavior of squat walls with steel and GFRP reinforcing bars owing to their different reinforcing schemes, tension-stiffening mechanisms, and material properties. Newly proposed equations outperform existing ones in terms of predicting the shear capacity of GFRP-reinforced squat walls. Furthermore, based on geometric and reinforcing attributes, a novel determinant index is derived for the classification of structural walls into squat and slender categories, which overcomes the limitations of prevalent methodologies based solely on aspect ratio. A practical method is suggested to adjust the failure mode of walls with GFRP reinforcing bars, incorporating a characteristic reinforcement ratio.

DOI:

10.14359/51740489


Document: 

22-429

Date: 

May 1, 2024

Author(s):

Bahareh Nader Tehrani, Ahmed Sabry Farghaly, and Brahim Benmokrane

Publication:

Structural Journal

Volume:

121

Issue:

3

Abstract:

While reinforcing bar lap splicing is inevitable in reinforced concrete (RC) structures, it critically affects structural behavior, especially in structures subjected to seismic load. That notwithstanding, current North American design standards do not provide any recommendations or equations for lap-spliced glass fiber-reinforced polymer (GFRP) reinforcing bars under seismic load. This study tested six full-scale RC columns measuring 1850 mm (73 in.) in height and 400 x 400 mm (16 x 16 in.) in cross section under constant axial load and incremental reversed cyclic lateral loading. Four columns were reinforced with GFRP bars, and two were reinforced with steel bars for comparison. The test parameters included lap-splice length and type of reinforcement. The structural performance of the specimens was evaluated based on the cracking behavior, failure mechanism, hysteretic response, load-carrying capacity, dissipated energy, stiffness degradation, and strain behavior. Afterward, available models in North American design standards for the splice length of GFRP reinforcing bars under monotonic loading were evaluated based on the experimental results. According to the results, providing adequate splice length can secure satisfactory structural performance in spliced GFRP-RC columns. The splice length determined based on the North American design standards for monotonic loading cannot, however, be directly used to achieve the required drift capacity in GFRP-RC columns under reversed cyclic lateral loading.

DOI:

10.14359/51740460


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