Comparative Study of Natural and Accelerated Carbonation Tests of HPC with Pozzolans: A Preliminary Approach

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Title: Comparative Study of Natural and Accelerated Carbonation Tests of HPC with Pozzolans: A Preliminary Approach

Author(s): G.C. Isaia, M. Vaghetti, and A.L.G. Gastaldini

Publication: Special Publication

Volume: 207

Issue:

Appears on pages(s): 467-488

Keywords: carbonation; concrete; pozzolans; strength

Date: 10/7/2002

Abstract:
Most of the carbonation studies are carried out by means of accelerated tests in conditioned chambers in order to obtain data in a shorter time, although the results are not always well correlated with field or laboratory data in natural tests. This work presents a comparative study between a reference portland cement concrete and pozzolanic mixtures with 10% to 50% fly ash, rice husk ash and silica fume in binary and ternary mixtures. Accelerated tests in a conditioned chamber with carbonation depth readings after 4, 8, 12 and 16 weeks, and natural tests with similar specimens exposed to the lab air environment with readings after 0.5, 1 and 2 years, were performed. The calculated rate between the carbonation coefficient of accelerated and natural tests was approximately 1 mm.week0.5 = 1 mm.year0.5 for concrete with w/cm < 0.45 and pozzolan contents up to 25%. For higher w/cm rates and w/cm < 0.45 and pozzolan contents up to 25%. For higher w/cm rates and pozzolan contents, the accelerated tests showed coefftcients 2 to 6 times higher than those observed in the natural test. This work presents preliminary data and it will be continued for 5 years more, in order to obtain readings after exposure to lab air for 4 and 8 years, after casting.