General Contractor Practice Exam

What effect do sulfate salts have on concrete?

1. Strengthens the mixture

2. Causes swelling and disintegration

3. Improves curing time

4. Increases durability

The correct answer is: Causes swelling and disintegration

Sulfate salts have a detrimental effect on concrete, primarily causing swelling and disintegration of the material. When sulfate ions infiltrate concrete, they can react with the hydration products of cement, particularly with tricalcium aluminate, resulting in the formation of expansive products like ettringite. This reaction leads to internal pressures within the concrete, ultimately causing cracking, spalling, and loss of structural integrity. This understanding emphasizes the importance of controlling sulfate exposure in concrete applications, especially in environments where sulfates are prevalent, such as soils or groundwater. Measures may include using sulfate-resistant cement or other modifications to mitigate the harmful effects of sulfate exposure on concrete structures. Hence, the correct answer accurately reflects the negative consequences sulfate salts impart on concrete.