Natural Carbonation Of Concrete

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Title: Natural Carbonation Of Concrete

Author(s): Federico M. Aguayo; Thano Drimalas; Kevin J. Folliard

Publication: Special Publication

Volume: 305

Issue:

Appears on pages(s): 2.1-2.12

Keywords: (Concrete, CO2 concentration, Exposure Site, Natural Carbonation, Supplementary Cementitious Materials)

Date: 9/1/2015

Abstract:

In this paper, the carbonation resistance of various concrete mixtures incorporating supplementary cementitious materials exposed to atmospheric CO2 concentration in Austin, Texas, USA, was investigated. The paper provides a detailed description on the creation of an outdoor exposure site to place and monitor concrete specimens under ambient air exposure conditions. Two exposure conditions were investigated, including specimens that were placed outdoors unsheltered and in sheltered environments protected from direct rainfall. The depth of carbonation was measured after 730 days of exposures. Additionally, relative humidity (RH), temperature, and environmental CO2 concentrations in the air were also monitored at the site to provide a general indication of the conditions at the exposure site. Various factors were investigated including water-cementitious materials ratio, type and dosage of supplementary material, and cement type. The depth of carbonation of mixtures without supplementary material was moderate. The addition of supplementary material significantly increased the carbonation depth, especially when replacement levels exceeded 30% of cement by mass. The results were exacerbated for those concrete specimens that were placed outdoors but sheltered from direct rainfall.