ACI-222R-19 Guide to Protection of Reinforcing Steel in Concrete against Corrosion

ACI-222R-19 Guide to Protection of Reinforcing Steel in Concrete against Corrosion. 4.2.1 Consideration of environmental conditions—The rate at which a structure is damaged by corrosion is depen- dent on the global and local environments in which the struc- ture is constructed. Chapter 3 provided information on the infuence of chlorides and carbonation on corrosion of steel in concrete. For an actively corroding structure, tempera- ture is also a signifcant environmental parameter. Environ- ments in which chlorides are present and CO 2 levels are high will require corrosion prevention strategies during design. Sohanghpurwala (2006) defnes corrosivity zones for the United States based on climatic conditions and the use of deicing salts. However, the author also reported signif- cant variation in input variables used to defne the zones and cautioned the reader on using these zones for design purposes. The designer should assess exposure conditions using generally available resources, but also exercise judg- ment regarding local environments and standards of practice. ACI 365.1R describes approaches to modeling the design service life and can assist in setting owner expectations. In addition to global environmental conditions, local envi- ronmental conditions can infuence the corrosion rate of the steel reinforcement (Lindvall 2000). For example, in concrete that is continuously submerged, the rate of corrosion is often low, limited by the rate of oxygen difusion (Gjorv et al. 1976; Kobayashi and Shuttoh 1991; Hussain et al. 2012; Guo et al. 2015). Alternatively, splash zones or concrete embedded in soil, where deicing salt runof occurs, are areas where high concentrations of chlorides can accumulate, which can lead to high rates of corrosion (Hansson et al. 2006). Thus, it is possible that diferent portions of the same structure might require diferent corrosion resistance strategies to achieve the design service life for the entire structure. 4.2.2 Consideration of structural design parameters— The detailing of a reinforced concrete structure is critical to its durability characteristics and service life. Adequate drainage and a method of removing drainage water from the structure are particularly important. Pockets that hold water or even horizontal surfaces that allow water to stand can lead to increased absorption of water containing aggressive ions (Hartt et al. 2004). Similarly, even vertical surfaces that stay damp for long periods may be subjected to a greater ingress of water and chlorides. For reinforced concrete structural members exposed to chlorides and subjected to intermittent wetting, the degree of protection against corrosion...