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International Concrete Abstracts Portal

Showing 1-5 of 2856 Abstracts search results

Document: 

23-122

Date: 

July 17, 2024

Author(s):

Shahid Ul Islam, Shakeel Ahmad Waseem

Publication:

Materials Journal

Abstract:

This study examines the impact of deicers on the compressive strength and microstructure of concrete at ambient temperature in sub-zero areas. In this study, after seven days of curing in plain water, concrete specimens were exposed to four deicer chemical solutions: sodium chloride, sodium acetate, calcium nitrate, and urea at 3%, 6%, and 9% concentrations, respectively. The specimens were tested for compressive strength after 14 days, 28 days, and 90 days of exposure. All tested deicers, except calcium nitrate, have a propensity to decrease the compressive strength of concrete. Exposure to sodium acetate, which appears to have the most detrimental effect, decreased the compressive strength of concrete by a maximum of 30.79% at a concentration of 9%, whereas exposure to calcium nitrate increased the compressive strength of concrete by 17% at a concentration of 3%. Deicers changed the microstructure of concrete, which was investigated using Field Emission Scanning Electron Microscopy (FESEM). This was followed by X-ray diffraction (XRD) for qualitative analysis of phases present in deicer-treated concrete specimens. The desirability function was used to determine the optimal exposure period and calcium nitrate concentration for concrete in subzero environments, which were respectively 10 to 11 days and 8.8 to 9%.

DOI:

10.14359/51742114


Document: 

22-298

Date: 

July 17, 2024

Author(s):

Junhyung Kim, Raissa Douglas Ferron

Publication:

Materials Journal

Abstract:

Embedding magnetic particles into cement paste produces a smart material in which the rheological properties of the resultant paste can be actively controlled through the use of magnetorheological principles. This research investigates the rheological behavior of cement-based MR pastes with and without air entrainment to gain a better understanding of the effects of air-entrained bubbles on MR cement pastes. Such information would be critical for the use of such MR Pastes in 3D concrete printing applications. It is revealed that the incorporation of entrained air results in increasing the MR response and this effect is related to the bubble bridge effect.

DOI:

10.14359/51742113


Document: 

23-036

Date: 

July 10, 2024

Author(s):

Jialuo He, Ayumi Manawadu, Yong Deng, Jie Zhao, and Xianming Shi

Publication:

Materials Journal

Abstract:

This laboratory study employed synthesized urea-formaldehyde (UF) microcapsules and polyvinyl alcohol (PVA) microfibers as a self-healing system to improve the durability of concrete in cold climates. The resistance of concrete specimens to rapid freeze-thaw (F/T) cycles was evaluated by measuring the change of relative dynamic modulus of elasticity (RDM) with respect to the number of F/T cycles. The control specimens (either with or without PVA microfibers) approached the failure state with a reduction of 38% in RDM after being subjected to 54 F/T cycles, whereas the self-healing specimens (either with or without PVA microfibers) remained in a good state with a reduction of approximately 10 to 15% in RDM after 732 F/T cycles. A polynomial regression model was developed to establish the relationship between the RDM and number of F/T cycles, and a three-parameter Weibull distribution model was employed to conduct the probabilistic damage analysis and characterize the relationship between the number of F/T cycles (N) and the damage level (D) with various reliabilities. The results revealed that the benefits of UF microcapsules and PVA microfibers to the frost durability of concrete diminish once the damage level exceeds a certain high level. Based on the Weibull distribution model, we established and validated the relationships between N and D by comparing the experimental data, the predicted data based on the nonlinear polynomial regression model, and the predicted data based on N-D relationships. The field service life of the self-healing concrete was then predictable at any given reliability.

DOI:

10.14359/51742036


Document: 

24-011

Date: 

July 10, 2024

Author(s):

Hyeonki Hong, Amreen Fatima, Anol Mukhopadhyay, Mary Beth D. Hueste, John Mander, Stefan Hurlebaus

Publication:

Materials Journal

Abstract:

Although ultra-high-performance concrete (UHPC) is one of the promising materials for precast bridge girder applications due to its advanced properties and durability, its implementation in the precast industry is subject to several potential concerns. To support implementation, this paper presents the development of nonproprietary UHPC mixtures for precast, pretensioned UHPC bridge girder applications. The nonproprietary UHPC mixtures were developed using materials commonly available in the Texas precast industry with the additional requirement of obtaining a compressive strength of 12-14 ksi (83–97 MPa) within 24 hours without any heat treatment while maintaining current precast, pretensioned bridge girder fabrication practices. The fresh, hardened, and durability properties of both lab- and plant-made UHPC mixtures were investigated. The research results show that selected nonproprietary UHPC mixture developed in a lab setting can be successfully produced in a precast plant setting with comparable properties.

DOI:

10.14359/51742043


Document: 

23-311

Date: 

July 10, 2024

Author(s):

Sathya Thukkaram, Arun Kumar A

Publication:

Materials Journal

Abstract:

Lightweight concrete (LWC) finds wide-ranging applications in the construction industry due to its reduced dead load, good fire resistance, and low thermal and acoustic conductivity. Lightweight geopolymer concrete (LWGC) is an emerging type of concrete that is garnering attention in the construction industry for its sustainable and eco-friendly properties. LWGC is produced by using geopolymer binders instead of cement, thereby reducing the carbon footprint associated with conventional concrete production. However, the absence of standard codes for geopolymer concrete restricts its widespread application. To address this limitation, an investigation focused on developing a new mixture design for LWGC by modifying the existing ACI 211.2-98 provisions has been carried out. In this study, crucial parameters of LWGC such as alkaline/binder ratio, molarity, silicate/hydroxide ratio, and curing temperature were established using machine learning techniques. As a result, a simple and efficient method for determining the mix proportions for LWGC has been proposed.

DOI:

10.14359/51742040


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