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International Concrete Abstracts Portal

Showing 1-5 of 248 Abstracts search results

Document: 

SP337

Date: 

January 30, 2020

Author(s):

ACI Committee 357 – Offshore and Marine Concrete Structures, Mohammad S. Khan

Publication:

Symposium Papers

Volume:

337

Abstract:

Offshore and marine concrete structures have not received enough attention in the recent past, at least in the United States. The complexity and safety concerns associated with these structures are such that they probably need more attention compared to many other types of concrete structures. Also, offshore and marine concrete structures are so global in nature that there is a higher need for better coordination and synchronization of design, construction, inspection, and maintenance practices in different parts of the world. A two-part session, titled “Offshore and Marine Concrete Structures: Past, Present, and Future,” was held at the Spring 2019 ACI Concrete Convention and Exposition on March 24-28 in Quebec City, Quebec, Canada. The session, sponsored by ACI Committee 357, Offshore and Marine Concrete Structures, highlighted accomplishments of the past, current state-of-the-practice, and a path for the future. This ACI Special Publication (SP) is a compilation of select papers presented at the session. The efforts of all the reviewers in assuring the quality of this publication is greatly acknowledged.


Document: 

SP-337_07

Date: 

January 23, 2020

Author(s):

Pericles C. Stivaros; Varoujan Hagopian; and Alan D. Pepin

Publication:

Symposium Papers

Volume:

337

Abstract:

This paper discusses the structural assessment and repair of a waterfront concrete pier. This paper also discusses the responsibilities of the construction team through the investigation and repair process. The apron around the pier is an exposed concrete deck supported on steel beams and concrete caissons. The concrete apron exhibited various deteriorated conditions, including cracking and spalling. The pier owner requested a structural condition survey of the pier apron to determine the extent of the damage and to develop a repair program.

The design team proposed an investigation and repair program in accordance with various industry standards, including ACI 357, ACI 562, and ACI 364.1R. The challenge of this project was the limited budget and time allocated by the owner to perform the investigation and repair. As a result, the investigation was limited to visual observations only, and the repairs were restricted to repairing unsafe conditions only. Despite the investigation and repair construction limitations, the design team work around the needs and budgets of the owner and managed to restore the structure to a safe condition. However, the effects of insufficient evaluation of the structure before rehabilitation, had an adverse effect on the project schedule and extent of repairs performed. Also, due to the project budget limitations, the responsibilities of the design team were challenged.


Document: 

SP-337_06

Date: 

January 23, 2020

Author(s):

Edward (Ted) Moffatt, Michael Thomas and Andrew Fahim

Publication:

Symposium Papers

Volume:

337

Abstract:

In 1978, the Canadian Centre of Mineral and Energy Technology (CANMET) initiated a longterm study to determine the performance of concrete in a marine environment. Between 1978 and 1994, over three hundred prisms as part of 14 different experimental phases were placed at the mid-tide level at the Treat Island exposure site. Treat Island is an outdoor exposure site operated by the U.S. Army Corps of Engineers, and lies in the Passamaquoddy Bay, part of the Bay of Fundy, near the town of Eastport in Maine. Following 25 years of exposure, the blocks were retrieved after being exposed to tidal conditions representing approximately 18,250 cycles of wetting and drying, and 2,500 cycles of freezing and thawing. This paper presents the durability performance of concrete from several phases of the CANMET study. This includes concrete incorporating various levels of supplementary cementing materials (up to 80% by mass of cementing material in some cases), with normal density and light-weight aggregate. The paper also compares output from the service-life model Life-365 with experimental chloride profile data. The results indicate the efficacy of SCMs in increasing the concrete resistance to chloride penetration. However, use of very high levels of these materials was found to render the concrete more susceptible to surface scaling. The results also showed that Life-365 model can predict chloride penetration adequately with very simple inputs.


Document: 

SP-337_08

Date: 

January 23, 2020

Author(s):

Anthony Devito; Alex Krutovskiy and Leszek Czajkowski

Publication:

Symposium Papers

Volume:

337

Abstract:

The purpose of the LaGuardia Runway Extension Project is to extend existing runways 4-22 and 13-31 into Flushing Bay, at the inshore end of Long Island Sound, to support Engineered Material Arresting System (EMAS) - a crushable material installed at the end of each runway to reduce the risk of a plane overrun during takeoff.

The new runway deck extensions are marine concrete structures which utilize precast prestressed pile caps with a pre and post-tensioned composite precast deck and cast-in-place concrete topping slab. The concrete decks are supported by 250 ton (227 tonnes) 24 inch (61cm) diameter epoxy coated closed end concrete filled steel pipe piles with specialized wraps and sacrificial zinc anodes for corrosion protection. The piles are approximately 100 feet (30m) long and driven in about 30 feet (9m) of water through soft organic clay and dense glacial soils and founded on bedrock.

This paper provides an overall description of the runway extensions and a detailed account of both the technical and logistical challenges. Challenges included a prestressed composite deck design for both the aircraft impact and braking loads. Maintaining and replacing the lightbars of the Approach Lighting Systems (ALS) used to visually identify the runways was required, along with optimizing the pile hammer selection and driveability with wave equation analyses and dynamic pile driving PDA testing. Extensive coordination was necessary with the PANYNJ, FAA and various other stakeholders involved in this fast-paced design build project.


Document: 

SP326-89

Date: 

August 10, 2018

Author(s):

Jeanette Visser

Publication:

Symposium Papers

Volume:

326

Abstract:

The lack of resistance models to determine the penetration of airborne chlorides into the concrete makes service-life prediction hardly possible for concrete structures exposed to chlorides, something badly needed as airborne chlorides can lead to severe bar corrosion even at 10 km (6 miles) from the sea. Predicting chloride penetration currently is performed by solving the diffusion equation assuming submerged conditions and trying to remedy the different load condition for airborne chlorides by empirical extensions. This has resulted in many different models, none of which satisfactory explained the observed chloride penetration. A different solution of the diffusion equation is provided in this paper, introducing a constant chloride flux into the boundary conditions. This constant chloride flux model relates also the diffusion coefficient to the surface concentration, a missing relation up to now. The proposed model has been shown to satisfactorily fit test results obtained in the wind tunnel, especially with respect to the amount of the chlorides taken up by the concrete and the total amount of chlorides deposited on the surface. The model can, therefore, appropriately describe airborne-chloride penetration, as long as chloride content at concrete surface does not reach its maximum. Furthermore, the constant chloride flux model describes quite well the differences observed between the chloride profiles resulting from a direct exposure to a marine environment for similar concrete mixes. Especially the low surface concentration founds for concretes with a high diffusion coefficient and high surface concentrations found for concrete with a low diffusion coefficient while exposed at the same location, are now well described.


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