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International Concrete Abstracts Portal

Showing 1-5 of 125 Abstracts search results

Document: 

18-347

Date: 

September 1, 2020

Author(s):

Song Wang and Mohamed A. ElGawady

Publication:

Materials Journal

Volume:

117

Issue:

5

Abstract:

In recent decades, concrete-filled fiber-reinforced polymer tube (CFFT) columns have gained increasing popularity in bridge construction as an alternative to conventional reinforced concrete columns. CFFT columns have excellent structural performance, which is attributed to the superior properties of the fiber-reinforced polymer (FRP) tubes. Furthermore, using FRP tubes eases the construction of CFFT columns. However, one obstacle hindering the greater acceptance of FRP as a common construction material in civil infrastructure application is the susceptibility of FRP to degradation during long-term exposure to a severe environment. The purpose of this study is to investigate the durability of CFFT columns subjected to seawater corrosion, which is the scenario for seashore bridges. CFFT stubs were immersed in simulated seawater with two different elevated temperatures for up to 450 days. Sustained axial loads were also applied to the stubs to simulate the real-life service load. Compression tests and hoop tensile tests were carried out on both pre- and post-conditioned specimens.

DOI:

10.14359/51724621


Document: 

19-416

Date: 

September 1, 2020

Author(s):

Ali F. Al-Khafaji, John J. Myers, and Antonio Nanni

Publication:

Materials Journal

Volume:

117

Issue:

5

Abstract:

Corrosion in reinforced concrete (RC) represents a serious issue in steel-reinforced concrete structures; therefore, finding an alternative to replace steel reinforcement with a non-corrosive material is necessary. One of these alternatives is glass fiber-reinforced polymer (GFRP) that arises as not only a feasible solution but also economical. The objective of this study is to assess the durability of GFRP bars in concrete bridges exposed to a real-time weather environment. The first bridge is Southview Bridge (in Missouri) and its GFRP bars have been in service for more than 11 years; the second bridge is Sierrita de la Cruz Creek Bridge (in Texas State) and its GFRP bars have been in service for more than 15 years. To observe any possible mechanical and chemical changes in the GFRP bars and concrete, several tests were conducted on the GFRP bars and surrounding concrete of the extracted cores. Carbonation depth, pH, and chlorides content were performed on the extracted concrete cores to evaluate the GFRP-surrounding environment and see how they influenced certain behaviors of GFRP bars. Scanning electron microscopy (SEM) was performed to observe any microstructural degradations within the GFRP bar and on the interfacial transition zone (ITZ). Energy dispersive spectroscopy (EDS) was applied to check for any chemical elemental changes. In addition, glass transition temperature (TA) and fiber content tests were carried out to assess the temperature state of the resin and check any loss in fiber content of the bar after these years of service. The results showed that there were no microstructural degradations in both bridges. EDS results were positive for one of the bridges, and they were negative with signs of leaching and alkali-hydrolysis attack on the other. Fiber content results for both bridges were within the permissible limits of ACI 440 standard. Carbonation depth was found only in one of the bridges. In addition, there were no signs of chloride attack in concrete. This study adds new evidence to the validation of the long-term durability of GFRP bars as concrete reinforcement used in field applications.

DOI:

10.14359/51725980


Document: 

19-322

Date: 

July 1, 2020

Author(s):

B. S. Sindu and Saptarshi Sasmal

Publication:

Materials Journal

Volume:

117

Issue:

4

Abstract:

To develop cementitious composites with improved properties, engineering has to be judiciously done at different scales. In this study, a multi-scale engineered cementitious composite (MS-ECC) with high tensile strength and strain-hardening properties is developed by incorporating nano-, micro-, and macro- (in the form of continuous fibers) fibers into it. At first, a cementitious composite is developed by individually incorporating nano- and microfibers to understand the influence of each type of fiber and to arrive at the optimum dosage level. Digital image correlation information is employed to investigate the crack properties and fracture process in the developed composite with individual scale fibers. Next, a hybrid cementitious composite, developed by incorporating nano- and microfibers, is found to demonstrate an improvement in the strength and strain hardening properties. Further improvement in higher scale is carried out by incorporating continuous fibers into it to develop MS-ECC which exhibited tensile strength of 23 MPa (3.63 ksi) and strain capacity more than 8000 micron.

DOI:

10.14359/51724625


Document: 

19-307

Date: 

July 1, 2020

Author(s):

Ishtiaque Tuhin and Mostafa Tazarv

Publication:

Materials Journal

Volume:

117

Issue:

4

Abstract:

Confinement enhances mechanical properties of concrete, especially the strain capacity. As a result, confined reinforced concrete (RC) members usually exhibit higher displacement capacities compared to unconfined members. Even though the behavior of concrete confined with external jackets has been extensively investigated in the past, confined properties of polyureajacketed concrete are largely unknown and were investigated in the present study. Thirty concrete cylinders were tested under slow uniaxial compression to investigate mechanical properties of polyurea-confined concrete and to establish stress-strain behavior. It was found that polyurea does not increase the strength of the confined sections under static loads. However, the compressive strain capacity of polyurea-confined concrete is more than 10%, equal to or higher than the reinforcing steel bar tensile strain capacity. Two uniaxial stress-strain models were developed for polyurea-confined concrete with circular sections under static loads. Analytical studies showed that the displacement ductility capacity of low-ductile bridge columns can be doubled using polyurea jackets. This unique property may make this type of confinement a viable retrofit or rehabilitation method to increase the displacement capacity of low-ductile members and structures in seismic regions.

DOI:

10.14359/51724617


Document: 

19-112

Date: 

March 1, 2020

Author(s):

Leonidas P. Emmenegger and Alberto A. Sagüés

Publication:

Materials Journal

Volume:

117

Issue:

2

Abstract:

Half-cell potential mapping is frequently used for the detection of corrosion in reinforced concrete. The procedure can be time-consuming and disruptive, partly due to the need for physical contact with the concrete surface. An alternative is presented in the form of a fast-responding, non-contacting electrode array that requires no surface pretreatment, and is suitable for mobile operation. This approach uses the vibrating Kelvin probe principle, with the electrode hovering over but not touching the concrete surface. Operation is demonstrated on an actual Florida bridge deck with a robust synchronized array as a model for lane-wide roadway scanning. The electrode-to-concrete (operating) surface gap can clear normal deck surface irregularities. Results replicated corrosion-identifying features from conventional half-cell electrode mapping without significant surface preparation or waiting for potential stabilization. The technology is promising for rapid corrosion assessment of bridges at low cost without extended lane closures.

DOI:

10.14359/51720306


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