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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 25 Abstracts search results

Document: 

SP122-08

Date: 

June 1, 1990

Author(s):

Kamal H. Khayat, Ben C. Gerwick, Jr. and Weston T. Hester

Publication:

Symposium Papers

Volume:

122

Abstract:

The underwater placement of small concrete volumes for repair operations necessitates that the fresh concrete be highly resistant to water erosion and segregation, as well as self-compacting and self-leveling. The hardened concrete must develop high wear resistance and excellent adhesion to underlying surfaces and reinforcing steel. Four potential repair concretes and one conventional tremie mixture were cast underwater in small and relatively shallow depressions using tremie pipes. Research findings indicate that an anti-washout admixture should be used to minimize the risks of water dilution and segregation and to enhance the spreadability and leveling of underwater-cast concrete. Proven concrete mixtures recommended in this research can produce relatively flat repair surfaces with in-place compressive strength in excess of 8000 psi (55.2 MPa) and relative density close to 100 percent of similar values for concrete cast and consolidated above water. Bond strength close to 400 psi (2.8 MPa) can develop between underwater-cast concrete and neighboring concrete repair surfaces.

DOI:

10.14359/2484


Document: 

SP122

Date: 

June 1, 1990

Author(s):

Editor: David Whiting / Co-Sponsored by: ACI Committees 201 and ACI Committee 222

Publication:

Symposium Papers

Volume:

122

Abstract:

"A collection of 24 papers form an international panel of experts on topics ranging from fundamental laboratory studies of concrete durability to case histories of concrete rehabilitation. The volume is arranged in three parts. Part 1: covers the more fundamental aspects and laboratory investigations. Topics include freeze-thaw resistance, durability of high strength concrete, corrosion of reinforcing steel, air voids in concrete, and effects of high range water-reducers. Part 2: covers field studies where concrete is exposed to natural conditions. Topics include carbonation of concrete, deicer scaling resistance of roller compacted concrete pavements, performance in marine environments, and microbiologically-induced deterioration. Part 3: covers case histories of the performance and rehabilitation of concrete structures in severe service environments. The types of structures include cooling tower shells, precast prestressed concrete conveyor bridge, heavy duty dock, elevated road way, and a masonry structure under corrosive exposure." Note: The individual papers are also available as .pdf downloads.. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP122

DOI:

10.14359/14155


Document: 

SP122-22

Date: 

June 1, 1990

Author(s):

D. Bjegovic, V. Ukraincik, and Z. Beus

Publication:

Symposium Papers

Volume:

122

Abstract:

A characteristic example of reinforced concrete structural damage in an urban environment after 25 years' service is the east end of a stadium in Zagreb, Yugoslavia, for 11,000 spectators. This paper presents research works that served as a basis for the design of repairs to prolong the structure's service life. The damage is classified by types. The basic causes of the damage are explained with a detailed description of the influence of carbon dioxide from the air on the concrete. The repair design is described. The basic principle in repairing the upper and lower surface of the stand was that the materials and construction methods must be compatible with the existing concrete and also meet durability criteria. The repair design prescribes conditions for the materials, construction methods, and durability criteria. The paper presents preliminary investigations to select the optimum composition of a mortar that complies with the criteria required by the design. The influence of two polymer dispersions based on acryl and latex, as well as the influence of silica fume added to the mortar, are investigated. To repair the stand slab, the selected mortar applied was the cement mortar modified by added silica fume and superplasticizer to obtain a dense and compact composition and increased chemical resistance. The proposed solution for the lower surface was shotcrete improved by special admixtures. In designing the overlay, care was exercised that the additional load should not require strengthening of the stand structure. Acceptance of the repair work performed is outlined.

DOI:

10.14359/3418


Document: 

SP122-04

Date: 

June 1, 1990

Author(s):

C. Andrade, C. Alonso, I. Rz-Maribona, and M. Garcia

Publication:

Symposium Papers

Volume:

122

Abstract:

The air or oxygen permeability of concrete is usually measured by means of techniques that utilize mechanical driving forces. Thus, air or oxygen is forced to pass through a piece of concrete using different mechanical pressures. The flow of gas so measured is used as an indication of concrete permeability and sometimes is also used to predict the durability of concrete reinforcements based on the relationship between anodic corrosion rate and amount of oxygen, which may be reduced in the cathodic areas. However, this extrapolation may lead to erroneous conclusions, because a dry concrete allows a higher amount of oxygen to pass through it than a wet one, although the corrosion rate should be much lower in dry than in wet concrete. In this paper, comparisons between flow of oxygen measured in paste, mortar, and concrete specimens held at different relative humidities using electrochemical driving forces (polarization at about -750 mV SCE), and corrosion rates (measured by means of polarization resistance) are presented to discuss the inherent relationships. The results show that the oxygen permeability is only dependent on the amount of electrolyte inside the pores, but the corrosion rate is also dependent on the concrete resistivity, which is fixed by the amount of pore water content.

DOI:

10.14359/2453


Document: 

SP122-12

Date: 

June 1, 1990

Author(s):

Joseph F. Lamond and M. K. Lee

Publication:

Symposium Papers

Volume:

122

Abstract:

The ultimate test of concrete durability to natural weathering is how it performs in the environment in which it is to serve. Laboratory testing yields valuable indications of service life and durability. However, the potential disrupting influences in nature are so numerous and variable that actual field exposures are highly desirable to assess the durability of concrete exposed to natural weathering The U.S. Army Corps of Engineers, through the Waterways Experiment Station, Structures Laboratory, maintains a natural weathering exposure station. It is located on Treat Island in Cobscook Bay near Eastport, Maine. This station has been in use since 1936 and is an ideal location for exposure tests, providing twice-daily tide reversals and severe winters. The average tidal range is about 18 ft (5.4 m) with a maximum of 28 ft (8.5 m) and a minimum of 13 ft (4 m). In the winter, the combined effect of air and water temperatures creates a condition at meantide where specimens are repeatedly thawed and frozen. There have been 23 completed investigations and many of these have been previously reported. There are currently 40 active investigations. Four of these investigations are briefly discussed in this paper.

DOI:

10.14359/3739


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