International Concrete Abstracts Portal

International Concrete Abstracts Portal

The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.

Showing 1-5 of 793 Abstracts search results

Document: 

23-346

Date: 

July 1, 2025

Author(s):

Yail J. Kim and Abdulaziz Alqurashi

Publication:

Structural Journal

Volume:

122

Issue:

4

Abstract:

This paper presents the torsional behavior of hollow reinforced concrete beams strengthened with carbon fiber-reinforced polymer (CFRP) U-wraps. Test parameters involve variable wall thickness in the section and the width and spacing of the externally bonded CFRP sheets. An experimental program is conducted with 27 beams (three unstrengthened and 24 strengthened) to examine their capacities, shear flows, and force distributions when incorporating a ratio of 0.27 to 0.46 between the areas of the hollow and gross cross sections. The stiffness and capacity of the test beams are dominated by the wall thickness, and the effectiveness of CFRP strengthening becomes pronounced as the void of the beams decreases. The presence of CFRP redistributes internal shear forces in the cross section, which is facilitated by narrowing the spacing of the U-wraps. The effective zone of CFRP retrofit is positioned near the outer boundary of the strengthened section. Regarding crack control, multiple discrete U-wraps with narrow spacings outperform wide U-wraps with enlarged spacings. While the location of a shear-flow path is dependent upon the wall thickness, the width of the U-wraps controls the effective shear-flow area of the beams. The size of the void is related to the stress levels of internal reinforcing components, including yield characteristics. Transverse stirrups are the principal load-bearing element for the unstrengthened beams; however, the reliance of the stirrups is reduced for the strengthened beams because the U-wraps take over portions of the torsional resistance. Through a machine learning approach combined with stochastic simulations, design recommendations are proposed.

DOI:

10.14359/51743305


Document: 

24-046

Date: 

July 1, 2025

Author(s):

Xinmin Zhang, Chaoyuan Wu, Zengwei Guo, Fanxiang Xia, and Xianhu Ruan

Publication:

Structural Journal

Volume:

122

Issue:

4

Abstract:

It is well known that the estimates of most shear capacity prediction models for reinforced concrete (RC) components are of high dispersion due to their elaborate failure mechanisms and elusive material variability. A probability prediction model is more appropriate for estimating the shear capacity of RC members than a deterministic prediction model. Therefore, this study proposed a probabilistic model to evaluate the shear capacity of RC T-beams and employed a Bayesian-Markov chain Monte Carlo (MCMC) approach to determine the posterior parameter in the shear strength prediction model by Bayesian updating. The analysis results indicate that the probabilistic model achieves minimal variance, offering the most accurate predictions that closely match test data compared with other prediction models. The shear capacity of a T-beam increases with changes in flange width and flange height ratio, but remains constant once beyond a certain level. The shear capacity varies rapidly when the shear-span ratio (λ) is less than 2.5 or larger than 4.0 due to a notable shift in the failure mechanism. Besides, the shear capacity raises linearly by increasing the characteristic value of stirrups (ρvfyv).

DOI:

10.14359/51745491


Document: 

24-250

Date: 

June 11, 2025

Author(s):

Pratik Gujar, Beng Wei Chong, Precious Aduwenye, Xijun Shi* and Zachary C. Grasley

Publication:

Materials Journal

Abstract:

This study investigates the feasibility of utilizing a hybrid combination of recycled steel fibers (RSF) obtained from scrap tires and manufactured steel fibers (MSF) in concrete developed for pavement overlay applications. A total of five concrete mixtures with different combinations of MSF and RSF, along with a reference concrete mixture, were studied to evaluate fresh and mechanical properties. The experimental findings demonstrate that the concretes incorporating a hybrid combination of RSF with hooked-end MSF exhibit comparable or higher splitting tensile strength, flexural strength, and residual flexural strength to that of concretes containing only hooked-end MSF, straight MSF, and RSF. This enhanced mechanical performance can be ascribed to the multiscale fiber reinforcement effect that controls different scales (micro to macro) of cracking, thereby providing higher resistance to crack propagation. The concretes containing only RSF show lower splitting tensile strength, flexural strength, and residual flexural strength compared to concrete solely reinforced with straight MSF or other steel fiber-reinforced concrete (SFRC) mixtures due to the presence of various impurities in the RSF, such as thick steel wires, residual rubber, and tire textiles. Interestingly, blending RSF with hooked-end MSF overcomes these limitations, enhancing tensile strength, flexural strength, and residual flexural strength, while significantly reducing costs and promoting sustainability. Lastly, the findings from the pavement overlay design suggest that utilizing a hybrid combination of RSF with hooked-end MSF can reduce the design thickness of bonded concrete overlays by 50% compared to plain concrete without fiber reinforcement, making it a practical and efficient solution.

DOI:

10.14359/51747871


Document: 

24-303

Date: 

June 11, 2025

Author(s):

Tarek Uddin Mohammed, Mohammad Zunaied Bin Harun, Chowdhury Zubayer Bin Zahid, and Redwan Ul Islam

Publication:

Materials Journal

Abstract:

This research investigates the impact of using washed waste fines (WWF), a byproduct from ready-mixed concrete (RMC) plants, as a partial replacement for natural sand in concrete. Cylindrical (100mm x 200mm) and cubic mortar specimens (50mm x 50mm x 50mm) were created with 20% WWF substitution. Hardened properties such as compressive strength, tensile strength, UPV, and durability parameters such as chloride migration coefficient and carbonation coefficient were evaluated. The study also examined the microstructure of concrete using a Scanning Electron Microscope (SEM). Results showed that incorporating WWF enhanced both the hardened and durability properties of concrete, increasing compressive strength by 25% compared to the control case. Additionally, WWF decreased the non-steady-state chloride migration and carbonation coefficients, indicating improved durability. SEM analysis revealed a denser microstructure, and WWF incorporation reduced the permeable porosity and absorption capacity of concrete.

DOI:

10.14359/51747872


Document: 

24-002

Date: 

May 14, 2025

Author(s):

Gabriel R. Johnson, Elizabeth S. M. Poblete, and Cameron D. Murray

Publication:

Structural Journal

Abstract:

To use alternative cements such as belitic calcium sulfoaluminate (BCSA) cement for structural concrete, perhaps the most important consideration is ensuring that the rectangular stress block parameters used in flexural strength design are still applicable. This article describes a complex experimental study consisting of flexural-compression specimens loaded to replicate the compression side of the stress distribution in a reinforced concrete beam. From these coupled compression-flexural tests, the shape of the stress distribution in a BCSA cement concrete specimen can be derived and used to develop equivalent rectangular stress distribution parameters. BCSA cement concrete and portland cement concrete (PCC) unreinforced flexural compression specimens with various water-cement ratios (w/c) were fabricated and tested at varying ages. The results from the BCSA cement concrete flexural compression specimens were compared with PCC tests, extensive historical PCC data, and design code values. The current code equations approximating the rectangular stress block were found to be equivalent or conservative for BCSA cement concrete flexural members within the strength range of 54 to 85 MPa (7.8 to 12.4 ksi). This should give designers confidence in using this cement for structural concrete.

DOI:

10.14359/51746814


12345...>>

Results Per Page 




Edit Module Settings to define Page Content Reviewer