Relative Effects of Sodium Chloride and Magnesium Chloride on Reinforced Concrete: State of the Art

Abstract

Magnesium chloride (MgCl2) use for snow and ice control is becoming a well-established practice but has been limited to the past 10 years. Impacts associated with sodium chloride (NaCl) use are well documented, but concerns have been raised regarding the potential effects of MgCl2 use on concrete and steel reinforcement. The British Columbia Ministry of Transportation intended to establish guidelines for MgCl2 use by highway maintenance contractors. Information was gathered from available literature and interviews with academia and industry. Generally, few studies directly and comprehensively address the topic, and although significant research efforts are currently under way, results are not expected for several years. Past laboratory studies suggest that MgCl2 reacts with cement paste to reduce concrete strength and degrade concrete. Studies also suggest that chloride ions associated with MgCl2 have higher diffusion coefficients than those associated with NaCl. Field studies are limited, but laboratory coefficients for chloride ion diffusion correlate with results of a field study conducted in Montana. Higher chloride diffusion coefficients can reduce the initiation time for chloride-induced corrosion of reinforcing steel. No evidence to date directly links the increased deterioration of a structure to MgCl2 use; however, the history of use is short, and caution is recommended until additional studies can establish more evidence.

Chloride Penetration Resistance of Concrete Sealer and Coating Systems

“…Although this chloride content exceeded the maximum allowable limit of 0.019-0.025%, it was significantly lower than the penetrated water-soluble chlorides caused by NaCl and MgCl 2 deicing chemicals. This is because the diffusion of CaCl 2 into concrete is slower than that of NaCl (Hooton, Julio-Betancourt 2005;Mussato et al 2004). In addition, calcium oxy-chloride forms in the presence of CaCl 2 .…”

“…This finding suggests that MgCl 2 could be more detrimental to cause corrosion of steel reinforcement in reinforced concrete. MgCl 2 diffuses into concrete much slower than NaCl and CaCl 2 (Hooton, Julio-Betancourt 2005;Mussato et al 2004). Yet the penetrated water-soluble chloride content was significantly higher in the case of exposure to MgCl 2 versus NaCl or CaCl 2 .…”

Deicer Impacts on Pavement Materials: Introduction and Recent Developments

“…The scaling of concrete in the presence of deicers, referred to as "salt scaling" has been recognized as the main cause of frost-related concrete deterioration, and has been found closely related to concrete quality (e.g., air entrainment level), weather conditions, and the number of freeze/thaw cycles [11][12][13][14]. Concrete damage from salt scaling was found to be significantly dependent on the salt type (sodium, potassium, magnesium or calcium chloride) and salts containing potassium seemed to cause more scaling damage for unknown reasons [15].…”

Effectiveness of anti-icing operations for snow and ice control of parking lots and sidewalks

“…This large cost includes the use of large amounts of road salts for de-icing and anti-icing operations to remove snow and ice from transportation facilities. However, salt is detrimental to the environment and has corrosive effects to the infrastructure and damages vehicles (Mussato et al 2004;NCHRP-577 2007;Shi et al 2009;Jain et al 2012). To reduce maintenance costs and the adverse effects of salts, a significant amount of efforts have been made to improve the efficiency and effectiveness of winter maintenance methods.…”