ABSTRACT

However, the most pronounced form of concrete deterioration in Africa is carbonation-induced corrosion, which normally develops into cracking, delamination and spalling of concrete cover. Several experimental investigations into parameters and design variables that influence reinforcement corrosion have been developed into various models. However, most of these models have been developed basing on short-term accelerated laboratory experiments and their results often show poor agreement with or large variations from the actual real life observations. Also in practice, durability design of concrete is prescriptively done by specifying a minimum concrete cover depending on the exposure conditions, water/cement ratio, compressive strength, corrosion resistance, and diameter of the steel bars. However, there are uncertainties associated with these parameters which are associated to: (i) heterogeneity of concrete, (ii) variability in cover depth, which also hinges on quality control and workmanship during construction, (iii) variability in air CO2 concentration, relative humidity and temperature of the environment (Zhang & Lounis

1 PAPER SUMMARY

In the recent times, the use of concrete has grown in application to residential, industrial, commercial, innovative structures and constructions. It is pertinent to know that many concrete structures fail to achieve their expected service life due to the limited scientific knowledge on service life design. These issues are some of the major challenges confronting the modern construction industry. Consequently, billions of money is spent annually on repair and maintenance of ageing concrete infrastructure. In 1990, the National Research Council report in the U.S. gave an estimated cost of $2 to $3 trillion required over the next 20 years to repair concrete structures deteriorated by reinforcement corrosion (Hoff 1991) Also, in Sub Sahara Africa and many other parts of the world, a lot of money is spent annually on repairs and rehabilitation of existing concrete structures. The dilemma that has been argued by researchers is the definition of serviceability limit state for evaluation of the service life of the concrete structure. The difficulty is compounded by a myriad of factors such as ageing, global warming, natural disaster, lack of adequate impermeability of concrete, steel corrosion, and internal material reactions (Swamy 2005). Li et al. (2006) suggests that most of the

2006). These factors eventually lead to considerable uncertainty in service life prediction.