Concrete is the most used material for infrastructure development. However, durability of these structures is one of the main concerns, as the expected service life is approaching more than a hundred years. Among the known durability issues for concrete, corrosion of reinforcing steel is the main problem. In concrete structures, reinforcing steel is protected due to the high alkaline environment provided by the pore solution (pH > 12.5 units). However, it may corrode if the protection is lost. The protection may be lost due to chloride attack or due to the neutralization of the concrete pore solution surrounding the reinforcing steel. This neutralization of the pore solution is also called
concrete carbonation. Concrete carbonation is the result of the reaction of hydrated cement compounds with atmospheric CO2. Carbonation reduces the pH of the concrete pore solution (pH ≈ 8 units), developing uniform corrosion in the reinforcing steel. In places with tropical climate, atmospheric conditions may encourage the CO2 aggressiveness. However, the carbonation rate depends on several factors such as the type and amount of cement, porosity of the material, and amount of pozzolanic additions. The porosity of concrete is related to the porosity of both the cement paste and the aggregate and the proper compaction during casting. The porosity of the cement paste is related to the water/cement ratio and the degree of hydration. From the durability point of view, it is accepted that the porosity of the cement paste is the one that controls
the porosity of concrete. According to the literature,
concrete’s porosity above 15% is an indication of bad quality and below 10% is an indication of good quality.
Normal aggregates used in concrete have absorption
levels in the range of 0.2% to 4% for coarse aggregate and 0.2 to 2% for fine aggregate [6]. However, some limestone aggregates have absorption levels above these values. And due to the high-absorption characteristics of the aggregate, concrete made with this material has porosity values above 15%, thus suggesting bad quality concrete fromthe durability
point of view. One way to prove if this material is suitable for durable concrete structures is by determining the carbonation coefficient of the material. However, as concrete carbonation 2 Advances in Materials Science and Engineering proceeds at a very low rate, the use of an accelerated carbonation chamber is required. Therefore, the objective of this investigation was to study the carbonation rates of concrete specimensmade with highabsorption limestone aggregate.
