Service Life Prediction Model for Concrete
Jessica Jackson, Technical Service Engineer
Under the jurisdiction of ACI committee 365, a new
service life prediction model for concrete structures has been
introduced. Developed by Professor Mike Thomas, University of
Toronto, LIFE-365 is to become the standard model for predicting
service life for the entire concrete industry. The first
production version was released in October 2000. The committee
is hoping for ACI acceptance of the model within 5 years.
This model uses four analyses to estimate total
cost of the structure over its predicted service life. They
1. Predicting the initiation period
(time to onset of corrosion)—uses Fick’s Second Law
(diffusion) to estimate the concentration of chlorides at the
reinforcing steel. Initiation begins when the chloride threshold
has been exceeded. The model also takes into consideration
average monthly temperatures of where the structure is located,
type of structure, and mix design.
2. Predicting the propagation period—the
time from when corrosion starts until the first repair is needed.
3. Determining the repair schedule after
the first repair—uses a 10 year repair schedule after the
first repairs, and includes cost for repairing up to 10% of the
total surface area at each repair.
4. Estimating the life cycle costs—based
on the initial concrete (and other protection) costs and future
repair costs. Costs are given on a discounted (today’s