Effect of micro-climate variations on carbonation rate of concrete in the inland environment

Department of Civil Engineering, The Federal Polytechnic Idah, Nigeria

Corresponding author: alhassanay@gmail.com

Abstract

In an inland environment, carbonation is the primary cause of initiation for potential corrosion of steel in reinforced concrete. This problem has been exacerbated over recent years by increased urbanisation and vehicular traffic, resulting in higher atmospheric carbon dioxide contents – a problem typical of economically active cities throughout the world. It is important that designers of reinforced concrete structures respond to these variations through appropriate specifications to ensure that structures perform satisfactorily over their intended service lives. This paper is part of a study undertaken to assess the carbonation of concretes exposed to a range of micro-climate variations in inland environments, particularly with variations in carbon dioxide content, temperature and relative humidity conditions with the intent of developing a prediction model for the rate of carbonation. Concretes samples were prepared using three binder types representing variations of blends with FA, GGBS and four w/b ratios ranging from 0.4 to 0.75 and subjected to different degrees of initial water curing (3, 7, 28 days). These samples were placed in three exposure conditions: indoors in laboratory air, outdoors sheltered from rain and sun and outdoors fully exposed to the elements. The depths of carbonation of these samples were monitored over a period of 24 months in order to determine the rates of carbonation. Concrete samples in the outdoor sheltered sites presented the highest rate of carbonation. Although samples in this exposure site carbonated faster, the risk of reinforcement corrosion is likely to be low because the samples are protected from direct moisture effect. Keywords: Carbonation, Corrosion, Reinforced concrete, Micro climate, Inland environments