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Home > Publications > 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
SP131-02
J. J. Basson and B. J. Addiss
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.
10.14359/1191
SP131-01
V. Ukraincik and D. Bjegovic
The greatest threat to the durability of reinforced concrete structures is the reinforcement corrosion. The paper presents the importance of the concrete protective cover and the conditions causing the reinforcement corrosion under the action of chlorides and carbonic acid. Processes of absorption, diffusion and flow, i.e. of transport of media through concrete depend on the pore system and the amount of water in the pores.Physical laws describing the penetration of aggressive agents into concre-te can serve as a basis for engineering calculations of reinforcement durability in the concrete as well as for the designing of the concrete cover. Physical laws and corresponding material parametars are briefly reviewed in the paper. For engineering purposes, in calculating the durability, four typical tasks can be solved. The processes of degradation depend on the pore system in the concrete structure, and the paper indicates some possible technological measures of structure modifications.
10.14359/10025
SP131-21
Arne Damgaard Jensen
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.
10.14359/1341
SP131-22
Michael A. Ozol and Donald O. Dusenberry
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.
10.14359/1342
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