North Carolina Building Contractor License Practice Exam

Which of the following substances can retard the setting of concrete?

1. Water

2. Salt

3. Sugar

4. Vinegar

The correct answer is: Sugar

Sugar is known to retard the setting of concrete due to its role in slowing down the hydration process of cement. When sugar is added to a concrete mix, it interferes with the chemical reactions that typically occur when water is added to cement. This can extend the working time of the concrete, allowing for more time to work with the mix before it hardens. This property can be particularly beneficial in hot weather conditions where the quick setting of concrete can pose challenges for placement and finishing. In controlled amounts, sugar can be used to improve the workability of concrete without compromising its final strength. On the other hand, while water is essential for hydration and is necessary for setting, it does not retard the setting process. Salt can influence concrete curing but is typically detrimental to concrete strength. Vinegar is an acid that can adversely affect concrete quality. Understanding these distinctions is crucial for effective concrete management and ensuring the desired properties of the final product.