Performance based durability design, carbonation part 1 – Benchmarking of European present design rules

Abstract

In each design situation the deemed-to-satisfy rules of selected countries were followed. The probabilistic calculations were mainly based on short-term carbonation data. However, some calculations were also based on long-term observation. The latter was implemented for independent validation purposes. The calculated reliability ranges are very broad and in some "unfavourable" situations, the deemed-to satisfy requirements do not guarantee the required limit state (LS) arget reliabilities for the particular exposure. In "favourable" situations less stringent demands would have been sufficient.

FE-Study on the Effect of Gradient Concrete on Early Constraint and Crack Risk

“…In a performance-based design concept, the aim is to predict the carbonation depth in concrete depending on the concrete age. One concept that is based on experimental observations and theoretically derived by diffusion theory can be found in the literature [4][5][6]39]. In this theory, carbon dioxide is diffused into concrete and reacts with non-carbonated calcium minerals in the concrete at the "moving carbonation boundary".…”

“…According to [4][5][6] the performance-based resistance to carbonation is highly dependent on the cement type. Cement CEM I (high hydration energy) has good carbonation resistance while CEM III (low hydration energy) has a poor one.…”

“…To account for environmental conditions (humidity, CO2 concentration, curing, wetting effects) additional factors are applied in [4][5][6].…”

“…The curves are calculated assuming a carbonation rate for CEM I of kNAC = 2.5 mm/year 0.5 and a carbonation rate for CEM III/B of kNAC = 4.5 mm/year 0.5 . Additionally, an execution tolerance of Δc = 10 mm, according to [4][5][6] and standard test conditions (ke = ka = kc = W(t) = 1) for carbonation rate were assumed. The following equation (10) was used:…”

“…The main influences are corrosion induced by carbonation of the concrete, corrosion induced by chloride, freeze-thaw attack, chemical attacks or abrasive wear as already stated in present codes such as [2]. In recent years, performance-based design concepts for durability of reinforced concrete structures against carbonation of the concrete have been developed (e.g., [3][4][5][6]). …”