Study on Mass and Performance Deterioration of Concrete Under Multiple Corrosive Environments

Area of Science:

• Materials Science
• Civil Engineering
• Corrosion Science

Background:

• Concrete durability is critical for infrastructure longevity.
• Understanding concrete's response to aggressive environments is essential for material selection and design.
• Chloride and sulfate attacks are major degradation mechanisms for concrete structures.

Purpose of the Study:

• To evaluate the corrosion behavior and durability of Portland cement concrete (PC) and slag-substituted concrete (G60).
• To compare the effects of different corrosive environments (NaCl, composite NaCl + Na2SO4) and exposure conditions (immersion, dry-wet cycles) on concrete.
• To assess the protective role of slag incorporation against chemical attack and salt crystallization.

Main Methods:

• Specimens of PC and G60 concrete were subjected to immersion in 3.5% NaCl and a composite solution (3.5% NaCl + 5.7% Na2SO4).
• Dry-wet cycles were employed to simulate accelerated weathering conditions.
• Mass changes, relative dynamic elastic modulus, and visual surface changes (spalling, efflorescence) were monitored over 540 days.

Main Results:

• Under pure NaCl or water, minimal degradation was observed in both concrete types.
• The composite solution induced severe spalling, with G60 showing approximately 1.4% mass loss and a modulus reduction to 90% after 540 days.
• Dry-wet cycling significantly accelerated degradation compared to immersion, leading to greater mass loss and modulus reduction.
• Slag incorporation enhanced resistance to ionic penetration but this benefit decreased with extended exposure and increased cycling.

Conclusions:

• Combined chloride and sulfate attack, especially under dry-wet cycles, poses a severe threat to concrete durability.
• While slag substitution improves initial resistance to corrosive ions, its long-term efficacy is limited under harsh conditions.
• Further research is needed to optimize slag utilization for enhanced concrete resilience in aggressive environments.