North Carolina Building Contractor License Practice Exam

What is the minimum frequency for taking strength test samples for slabs placed?

1. Once per 5,000 square feet

2. Once per 2,500 square feet

3. Once per 10,000 square feet

4. Once per 1,000 square feet

The correct answer is: Once per 5,000 square feet

The correct answer is based on the guidelines set forth by the American Concrete Institute (ACI) and the standards adopted in the industry for concrete construction. The minimum frequency for taking strength test samples for slabs placed is established as once per 5,000 square feet. This practice ensures that the quality and integrity of the concrete are adequately monitored over large areas, allowing for timely identification of potential issues with the concrete's strength. Taking samples at this frequency strikes a balance between maintaining quality standards and being practical in terms of resources and time. It ensures that there are enough data points to assess the overall strength of the slab while not being overly burdensome on the construction process. Other options suggest varying frequencies that do not align with established industry practices. For instance, testing at intervals smaller than 5,000 square feet may lead to unnecessary costs and labor without significantly improving quality assurance, while larger intervals may not provide sufficient monitoring for quality control during larger slab installations. Thus, adhering to the standard of once per 5,000 square feet provides an effective protocol for ensuring concrete quality.