ACI Certification Practice Exam

What must be protected to ensure quality when obtaining a concrete sample?

1. Rapid mixing

2. Proper drying

3. Contamination and rapid evaporation

4. Environmental temperature

The correct answer is: Contamination and rapid evaporation

To ensure the quality of a concrete sample, protecting it from contamination and rapid evaporation is crucial. Contamination can occur from external sources such as dirt, dust, or mixing with other materials, which can alter the chemical composition or performance characteristics of the concrete. Protecting against contamination ensures that the sample accurately reflects the intended mix design. Rapid evaporation is another significant concern, particularly in warmer or windy conditions. When concrete is exposed to air, moisture can evaporate quickly, leading to issues such as crusting or incomplete hydration of the cement. This could ultimately affect the strength and durability of the concrete when it is cured. Therefore, it is essential to use proper methods to shield the sample from environmental factors and maintain its integrity until testing can take place.