North Carolina General Contractors Practice Exam

What do superplasticizers do in a concrete mixture?

1. Decrease the amount of water needed

2. Increase the set time

3. Enhance the mixing speed

4. Improve the appearance of concrete

The correct answer is: Decrease the amount of water needed

Superplasticizers are chemical additives used in concrete mixtures to significantly improve the flow properties of the mixture. The primary function of superplasticizers is to decrease the amount of water required to achieve a given workability or fluidity in the concrete. This reduction in water not only improves the strength and durability of the concrete once it cures but also minimizes the risk of excessive shrinkage and cracking. By allowing concrete to maintain a high level of workability with lower water content, superplasticizers help in achieving denser and more robust concrete structures. This is particularly important in applications where the concrete needs to flow into complex forms or around reinforcement bars. While their influence on set time, mixing speed, or appearance may vary based on specific formulations, these are not their primary functions and do not underscore the main benefit of superplasticizers in concrete technology.