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International Concrete Abstracts Portal

Showing 1-5 of 10 Abstracts search results

Document: 

SP331

Date: 

March 1, 2019

Author(s):

ACI Committee 345, ACI Committee 201, Yail J. Kim, Isamu Yoshitake, and Mark F. Green

Publication:

Symposium Papers

Volume:

331

Abstract:

Sustainability is one of the salient requirements in modern society. Structures frequently deteriorate because of aggressive service environments; consequently, federal and state agencies expend significant endeavors to maintain the quality of the structures. Among many factors, durability plays a major role in accomplishing the concept of sustainability. Extensive research has been conducted to understand the deterioration mechanisms of concrete and to extend the longevity of concrete members. Over the past decades, the advancement of technologies has resulted in durable construction materials such as advanced composites. This Special Publication (SP) contains nine papers selected from two technical sessions held in the ACI Spring Convention at Detroit, MI, in March 2017. All manuscripts were reviewed by at least two experts in accordance with the ACI publication policy.


Document: 

SP331-07

Date: 

February 1, 2019

Author(s):

Yasir M. Saeed and Franz N. Rad

Publication:

Symposium Papers

Volume:

331

Abstract:

This paper presents the experimental investigation of concrete beams pre-tensioned with Carbon Fiber Reinforced Polymer (CFRP) strands. Four rectangular prestressed concrete beams were fabricated and tested under cyclic loading, and then the beams were loaded monotonically until failure. All beams were prestressed with one 0.5-in. diameter (13 mm) CFRP strand. The results showed that bond failure between CFRP strands and surrounding concrete was the main cause of early and brittle failures. Adding extra steel stirrups improved the slippage resistance capacity but was not adequate to prevent slippage at higher loads. A new technique was developed and used by anchoring the CFRP strand at the ends using a steel-tube anchorage system. The new technique prevented the slippage and improved the flexural moment capacity by 39%. An analytical computer model was created to predict the load vs. deflection responses of the beams. The behavior of beams with CFRP strands were compared to beams with steel strands using the same computer program. It was found that CFRP beams had more flexural strength but lower ductility if both beams were designed to carry the same service loads.


Document: 

SP331-05

Date: 

February 1, 2019

Author(s):

Omid Gooranorimi, Doug Gremel, John J. Myers, Antonio Nanni

Publication:

Symposium Papers

Volume:

331

Abstract:

Glass fiber reinforced polymer (GFRP) bars are emerging as a feasible, economical solution to eliminate the corrosion problem of steel reinforcements in concrete structures. Confirmation of GFRP long-term durability is crucial to extend its application especially in structures exposed to aggressive environments. The objective of this study is to investigate the performance of GFRP bars exposed to the concrete alkalinity and ambient condition in two bridges with more than a decade old located in the City of Rolla, Missouri: i) Walker Bridge (built in 1999), which consists of GFRP-reinforced concrete box culverts; and; ii) Southview Bridge (built in 2004), which incorporates GFRP bars in the post-tensioned concrete deck. In order to monitor the possible changes in GFRP and concrete after years of service, samples were extracted from both bridges for various analyses. Carbonation depth, chloride diffusion, and pH of the concrete surrounding the GFRP bars were measured. Scanning electron microscopy (SEM) imaging and energy dispersive X-ray spectroscopy (EDS) were performed to monitor any microstructural degradation or change in the GFRP chemical compositions. Finally, GFRP horizontal shear strength, glass transition temperature (Tg) and fiber content were determined and compared with the results of similar tests performed on pristine samples produced in 2015. SEM and EDS did not show any sign of GFRP microstructural deterioration or existence of a chemical attack. Horizontal shear strength and Tg showed slight improvements while the fiber content was similar to the pristine values. The results of this study suggest that GFRP bars maintained their microstructural integrity and mechanical properties during years of service as concrete reinforcement in both bridges.


Document: 

SP331-02

Date: 

February 1, 2019

Author(s):

Ian Shaw, Hang Zhao and Bassem Andrawes

Publication:

Symposium Papers

Volume:

331

Abstract:

Fiber reinforced polymer (FRP) composites have emerged as a lightweight and efficient repair and retrofit material for many concrete infrastructure applications. FRP can be applied to concrete using many techniques, but primarily as either externally bonded laminates or near-surface mounted bars or plates. This paper presents the results of direct shear pull-out tests performed on aged concrete specimens reinforced with glass FRP (GFRP) and carbon FRP (CFRP) externally bonded laminates and near surface mounted (NSM) bars. An accelerated aging scheme consisting of freeze/thaw cycling in the presence of a deicing salt solution is implemented to determine the effect of long-term environmental exposure on the FRP/concrete interface in regions that experience aggressive winter environments. The results show that the NSM bar technique is superior to externally bonded laminates in terms of efficiency in the use of FRP material and the effects of accelerated aging. Generally, the performance of GFRP is affected less than CFRP after freeze/thaw cycling for both externally bonded laminates and NSM bars. For high strength NSM FRP bar applications, a spalled or cracked concrete surface caused by freeze/thaw cycling may drastically reduce the capacity of the FRP/concrete interface by inducing failure at the concrete/epoxy filler interface.


Document: 

SP331-01

Date: 

February 1, 2019

Author(s):

Tarek Omar and Moncef L. Nehdi

Publication:

Symposium Papers

Volume:

331

Abstract:

Bridge deck condition assessment is commonly conducted through visual inspection by bridge inspectors. Considering the colossal backlog of aging bridge structures, there is a need to develop cost-effective and innovative solutions to evaluate bridge deck conditions on regular time intervals, without interrupting traffic. This makes remote sensing technologies viable options in the field of bridge inspection. This paper explores the potential for applying infrared thermography (IRT) using unmanned aerial vehicle (UAV) to detect and quantify subsurface delaminations in concrete bridge decks. The UAV-borne thermal sensing system focuses on acquiring thermal imagery using a UAV and extracting information from the image data. Two in-service concrete bridge decks were inspected using a high resolution thermal camera mounted on a UAV. The captured images were then enhanced and stitched together using a tailored procedure to produce a mosaic view of the entire bridge deck, indicating the size and geometry of the detected delaminated areas. The results were validated by conducting hammer sounding and half-cell potential testing on the same bridge decks. The findings reveal the capability of the technology to provide measurements comparable to those derived from traditional hands-on inspection methods. Thus, it can be an excellent aid in efficient bridge maintenance and repair decision-making.


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