Service Life & Life Extension

Humans have been designing concrete structures or structures that use cementitious materials for ages without much thought given as to how long such structures would remain serviceable. Engineers knew that concrete hydration is a never ending reaction and concrete would keep on gaining strength if other negative factors (chemical, environmental, loading, etc.) do not slow that process or render it irrelevant.

Engineers designing concrete building or non-building structures produce designs that are expected to carry the loads safely and remain serviceable for the design life of the structure and outlive that design life, often being limited only by fatigue life or the severity of other factors. For wind turbine foundations, the specified design fatigue life was 20 years in early 2000s and was since increased to 25, 30 or even more years. For all types of structures, service life of concrete members or systems can be expected to be affected by various deterioration mechanisms, such as corrosion, cracking, freeze-thaw, alkali-aggregate reaction, etc.

Service life prediction of concrete structures is the focus of a design specification being developed by Committee 365 of the American Concrete Institute (ACI). A public discussion draft version of ACI CODE-365 is currently available and ACI are seeking public comments. CODE-365 is open for public comment February 11, 2024, until March 27, 2024. The draft and the public comments form can be obtained from ACI.

The proposed code introduces and defines roles and concepts such as service life engineer, durability limit states, predicted service life, service life prediction approaches, end-of-service criteria, etc.

It is of note that the proposed ACI CODE-365 applies only to new concrete structures. It is not intended for assessing the condition of existing structures or for estimating their remaining useful life (RUL).