The Risk of Corrosion of Steel in Recycled Aggregate Concrete

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Title: The Risk of Corrosion of Steel in Recycled Aggregate Concrete

Author(s): L. Friedl, A. Volkwein, and P. SchieBl

Publication: Special Publication

Volume: 212

Issue:

Appears on pages(s): 1055-1072

Keywords: chlorides; corrosion; recycled aggregate concrete

Date: 6/1/2003

Abstract:
Contrary to ordinary concrete, where penetration of chlorides is caused by sources outside the concrete, recycled aggregate concrete has an additional source of chlorides, when chloride-contaminated concrete is used as aggregate inside the new concrete. Therefore special specimens were developed to simulate the transport of water and chlorides from recycled aggregate to the surrounding concrete matrix. Conventional methods like weighing and chemical analysis were used to measure the chloride and water transport. It was established, that the pretreatment of recycled aggregate (e.g. moistening) has a large effect on the quantity and the speed of redistribution of chlorides between recycled aggregate and the new matrix. Additional tests with conventional concrete corrosion cells, where individual chloride contaminated recycled aggregates were placed near the embedded steel, showed intense pitting corrosion already after 90 d. The results of rapid chloride migration tests and capillary suction tests are pre- sented for the penetration of chloride and water from outside. For these investigations the composition of the recycled aggregate concrete, especially the type and the proportion of recycled aggregate were varied. The results indicate that the quantity of recycled aggregate has a minor influence on chloride ingress. However, the concrete composition and the type of recycled aggregate can enhance the chloride ingress into recycled aggregate concrete.