Effects of Deicing Chemicals on Concrete Durability
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This paper investigates the effects of various deicing chemicals, including sodium chloride, calcium chloride, magnesium chloride, and calcium magnesium acetate, on concrete durability under wetting and drying cycles at different concentrations.
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Research summary
Key Insights: Effects of Deicing Chemicals on Concrete Durability
This ACI technical paper reveals that certain common deicing chemicals, especially at higher concentrations and under wetting-drying cycles, can significantly degrade concrete over time, leading to reduced stiffness and strength, even without freeze-thaw action.
Research Focus
This research addressed the critical question of how different deicing chemicals impact concrete durability beyond just freeze-thaw scaling. Understanding these effects is vital for transportation infrastructure engineers and specifiers who must select materials and deicers that ensure long-term performance and safety. The study employed a controlled laboratory approach, exposing concrete specimens to cyclic wetting and drying in solutions of various deicing chemicals at concentrations relevant to field applications.
What the Research Found
Finding 1: Concentration and Chemical Type Dramatically Influence Damage
While lower concentrations of sodium chloride (NaCl) and calcium chloride (CaCl₂) showed minor negative impacts, higher concentrations of these, along with magnesium chloride (MgCl₂) and calcium magnesium acetate (CMA), caused significant material loss and reduced stiffness. This highlights that not all deicers are equal in their aggressive potential.
Finding 2: Wetting and Drying Cycles Amplify Deicer Damage
Unlike freeze-thaw conditions where damage might peak at intermediate concentrations, this study found that concrete deterioration due to wetting and drying cycles generally increases with higher deicer concentrations. This is crucial because deicer concentrations can build up within concrete structures over time.
Finding 3: Specific Chemical Reactions Cause Material Degradation
Beyond physical salt crystallization, chemical interactions within the cement paste, such as the formation of magnesium silicate hydrate with MgCl₂ and CMA, directly convert durable cementitious compounds into weaker, non-cementitious materials. This internal chemical attack poses a long-term threat to concrete integrity.
Why It Matters for Practice
These findings challenge the assumption that deicer damage is solely a freeze-thaw phenomenon. They underscore the need for engineers to consider the chemical composition and concentration of deicers used on concrete structures, especially those subjected to frequent wetting and drying, such as bridge decks and parking structures. This research opens opportunities for more informed material selection and the development of more resilient concrete mixes.
Putting It Into Practice
Based on these findings, professionals should consider:
- • Deicer Selection: Prioritize deicers with a lower known potential for chemical attack on cementitious materials.
- • Concentration Management: Understand that higher concentrations are more aggressive under wetting-drying conditions.
- • Concrete Mix Design: Investigate the use of supplementary cementitious materials (SCMs) or specialized admixtures that can enhance resistance to chemical attack.
- • Durability Specifications: Review and potentially update specifications for concrete exposed to deicing chemicals, particularly for critical infrastructure.
Limitations to Note
The study focused on specific wetting and drying cycles and concentrations. Real-world conditions may involve more