Carbonation Depths of Concrete with and without Condensed Silica Fume

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Title: Carbonation Depths of Concrete with and without Condensed Silica Fume

Author(s): O. Skjolsvold

Publication: Special Publication

Volume: 91

Issue:

Appears on pages(s): 1031-1048

Keywords: beams (supports); carbonation; concrete cores; concrete slabs; permeability; reinforced concrete; silica; strength; water-cement ratio.

Date: 2/1/1986

Abstract:
Cores were drilled from 16 structures with silica fume concrete (SC-concrete) and 11 without it (OPC-concrete). The nominal strength of the concretes was 25 MPa. Testing was done at different periods. Carbonation depths were corrected to 60 months and 33 MPa. The mean corrected carbonation depth for all structures with SC-concrete was 11.6mm. The corresponding value was 8.8mm, for OPC-concrete. However, the dispersion in the results was to high to make conclusions. The standard deviati-ons were 5.9mm and 2.4mm respectively for SC- and OPC-concrete. Considering statistical variation in carbonation depths and concrete cover over the reinforcement, the observed carbonation depths indicate an initiation period for corrosion as short as 2 - 3 years for both types of concrete at the stated strength level. This initiation period is very short. Carbonation depths were also measured on beams and slabs that were cured under different curing conditions. Curing conditions had significant effect. The rate of carbonation was proportional to the water/cement-ratio. Therefore the compressive strength is an unreliable parameter to judge the quality of concrete containing condensed silica fume.