International Concrete Abstracts Portal

Showing 1-5 of 23 Abstracts search results

Document: 

SP131-20

Date: 

March 1, 1992

Author(s):

R. Kristjansson and H. Olafsson

Publication:

Symposium Papers

Volume:

131

Abstract:

As the sole domestic building material in Iceland, concrete is widely used for house construction as well as for other construction, such as dams, bridges, and harbors. In Iceland, conditions are in many ways extreme: the climatic conditions are harsh, the cement is high in alkalies, aggregates are of varying quality (some being reactive), and codes and standards have been sparse. Field surveys have shown that alkali-aggregate reaction (AAR) damage occurs where no preventive measures were taken and other conditions were unfavorable. Preventive measures taken in dam and bridge construction have proven to be effective. No AAR damage has been found in constructions erected after 1979, when several preventive measures were taken. The most important one is 5 to 7+ percent replacement of cement with silica fume Stricter criteria have been enforced to secure freeze-thaw durability, and durability design is improving. Research in repair and maintenance methods has had considerable influence on the construction industry.

DOI:

10.14359/1340


Document: 

SP131-21

Date: 

March 1, 1992

Author(s):

Arne Damgaard Jensen

Publication:

Symposium Papers

Volume:

131

Abstract:

Concrete roads have been in use in Denmark since 1923. Many of the old roads are still in use today and exhibit excellent durability. The Danish Technological Institute has investigated some of the old roads from the 1930s. The investigations include thin-section analysis of cores from the roads. This technique was used extensively by G. M. Idorn during the 1950s and 1960s, and in the late 1970s, the technique was further developed by the Danish Technological Institute. The results of the investigation show that the old durable concrete is a dense, strong concrete without signs of internal deterioration.

DOI:

10.14359/1341


Document: 

SP131-22

Date: 

March 1, 1992

Author(s):

Michael A. Ozol and Donald O. Dusenberry

Publication:

Symposium Papers

Volume:

131

Abstract:

Five dormitory buildings on the Amherst College campus in Amherst, Massachusetts have essentially identical exposed aggregate precast concrete curtainwall panels. The panels on the three buildings that were constructed in 1963 are severely cracked and spalled; the buildings constructed in 1964 are relatively free of deterioration. The concrete used in the panels of all the buildings is composed of crushed quartz coarse and fine aggregate with strong and hard portland cement paste with low water-cement ratio and low void content. The significant difference between the materials used in the buildings is the amount of alkalies: the alkali content of the portland cement in the 1963 buildings is almost twice as high as in the 1964 buildings. A network of fine cracks developed in the panels due to alkali-silica reaction. These cracks allowed water to enter the panels and freeze during cold weather. The resulting progressive damage has led to disintegration of the cement paste, severe spalling, and corrosion of the reinforcing steel. The phased repair program, which began in the summer of 1989 and is expected to require several years to complete, involves removal and/or replacement of severely damaged panels, repair of damaged panels in place, modification of structural and waterproofing details to reduce exposure, and treating of undamaged panels to prolong their life.

DOI:

10.14359/1342


Document: 

SP131-02

Date: 

March 1, 1992

Author(s):

J. J. Basson and B. J. Addiss

Publication:

Symposium Papers

Volume:

131

Abstract:

Mechanisms of corrosion of concrete have been extensively studied and elucidated by various workers, but rate-determining factors have been neglected, as have the interactions between different corrodents. However, by considering all relevant influences as part of the total corrosive environment, it is possible to quantify aggressiveness as indexes and use them to select the appropriate technology for the circumstances under consideration.

DOI:

10.14359/1191


Document: 

SP131-04

Date: 

March 1, 1992

Author(s):

M. J. Simon, R. B. Jenkins, and K. C. Hover

Publication:

Symposium Papers

Volume:

131

Abstract:

Experiments were conducted to determine the influence of immersion vibration on the air-void system parameters of air-entrained concrete, as a function of both radial distance and depth from the point of vibrator insertion. For a 1½ in. (40 mm) diameter immersion vibrator, one could conclude that vibration has little or no effect on air-void systems at distances of 5, 8, or 10 in. (125, 200, or 250 mm) from the point of insertion. The same vibrator in the same concrete can reduce the total air content by 50 percent, and increase specific surface by as much as 100 percent directly at the point of vibrator insertion. Which particular effect one may observe in hardened concrete, therefore, depends on the selection of core location relative to point of vibrator insertion. These observations have implications for specifying, casting, and testing air-entrained concrete.

DOI:

10.14359/1203


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