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  • 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.

International Concrete Abstracts Portal

Showing 1-5 of 278 Abstracts search results

Document: 

SP-337_05

Date: 

January 23, 2020

Author(s):

Kjell Tore Fosså and Widianto

Publication:

Symposium Papers

Volume:

337

Abstract:

This paper describes the development in concrete technology for offshore concrete structures from the 1970’s until now and discusses some potential topics for future research which would result in more cost-effective offshore concrete structures.

Most of the offshore concrete structures constructed in the last 4 decades are still in operation, with no or only minor maintenance required, even though the average age for these structures in the North Sea is more than 25 years. The compressive strength in offshore structures has gradually increased from about 40MPa (5800 psi) in the 1970’s to more than 100MPa (14500 psi) in some of the latest concrete structures. Standards and concrete specifications have been revised several times during these years. In parallel, the knowledge from several research and development programs has been used to further improve the concrete properties and overcome the limitations. Focus has been primarily to improve the compressive strength of the concrete as well as the durability and concrete workability. The cement and admixture industry have been heavily involved in research programs to further adapt and develop these material properties. The result of the product developments in the concrete constituency has also improved cost-effectiveness and durability (including overall life-cycle cost-effectiveness) for offshore concrete structures.

With the new generation technology, the technical limitations we face today will be overcome. With more knowledge and improved technology, the quantity and size of cracks in concrete in service are expected to be reduced, which would also improve durability. In addition, the focus in the future will also be on sustainable and environmentally friendly materials.


Document: 

SP-334-02

Date: 

September 30, 2019

Author(s):

Anol Mukhopadhyay and Xijun Shi

Publication:

Symposium Papers

Volume:

334

Abstract:

Potential issues associated with depletion of good aggregate sources and management of excess RAP stockpiles increasingly motivate use of RAP in PCC as a coarse aggregate replacement. Texas has shown great interest in disposing excess RAP stockpiles and a systematic study on using RAP in PCC for Texas pavement applications was conducted by the authors recently. This paper provides a concise summary of the findings from this study. The major conclusions are (1) PCC mixture with dense aggregate gradation can be achieved by adding coarse RAP with adequate intermediate sized particles, which offers better overall performance in terms of workability and mechanical properties, (2) RAP-PCC with coarse RAP replacement up to 40% showed considerable reduction for modulus of rupture. Asphalt cohesive failure (crack passing through the asphalt layer) was found to be the main mechanism responsible for the strength reductions, (3) the addition of allowable amounts of RAP into PCC provides equivalent durability performance relative to plain PCC, and (4) constructing pavements with RAP-PCC yields economic, environmental and social benefits.


Document: 

SP-334-13

Date: 

September 30, 2019

Author(s):

Luz Angélica Rodríguez-Bello, Pedro Nel Quiroga, Juan Pablo Agudelo, and María Paulina Villegas-De-Brigard

Publication:

Symposium Papers

Volume:

334

Abstract:

Construction and demolition waste (CDW) has become an environmental, social and economic problem in some regions. Many initiatives to increase CDW recycling and concrete with recycled aggregates have failed or have not accomplished the goals, due to the lack of good management. In Bogotá, even though regulations establish that 25% must be harnessed, only 17% is achieved. To obtain rates as high as the global ones, a CDW diagnosis in works is run and policy instruments that would allow the application of a circular economy concept as opposed to a linear economy are determined. It is found that economic and informative instruments are the most popular worldwide and the most requested at the national level, in comparison to regulatory instruments which currently prevail in Bogotá. Likewise, the literature highlights prevention actions and the national context prefers recycling and disposition actions.


Document: 

SP-332_02

Date: 

July 1, 2019

Author(s):

Pericles C. Stivaros

Publication:

Symposium Papers

Volume:

332

Abstract:

A successful concrete repair project requires a close coordination of efforts between the three major parties involved: the owner, the licensed design professional (LDP), and the contractor. Lack of coordination and clear understanding of the professional and contractual responsibilities, as well as the expectations, of each party involved in a concrete repair project, could result in long legal disputes to attempt to sort out the responsibilities of each party. The greatest victim of the dispute is usually the structure itself. The American Concrete Institute (ACI) has led the effort to develop responsibility guidelines in concrete construction. ACI 132 identifies and suggests the allocation of responsibilities to various parties involved in concrete construction. ACI 132 document is applicable to general concrete construction, and it does not consider the particularities of evaluating and repairing existing concrete structures. ACI 562 provides minimum requirements for assessment, repair and rehabilitation of existing distressed concrete structures, including a discussion on the responsibilities of the licensed design professional for the evaluation and repair of concrete structures. This paper discusses the responsibilities of the licensed design professional, the contractor, and the owner through a repair case study. The paper demonstrates the need to expand ACI 132 and/or ACI 562 to include responsibility guidelines for concrete repair projects.


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.


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