Florida DOT Concrete Batchman/Operator Practice Exam

Which type of admixture should NOT be used in drilled shaft concrete?

1. Type A

2. Type B

3. Type F, Type G, Type I, Type II

4. Type C

The correct answer is: Type F, Type G, Type I, Type II

The selection of admixtures for concrete in specific applications, such as drilled shaft concrete, is crucial for ensuring the desired performance and longevity of the structure. In this context, Type F, Type G, Type I, and Type II admixtures are generally known for their specific functions, including water-reduction properties, high strength, or improved durability. However, these types may interfere with the drilling process or the performance of the concrete once it is set, particularly in the context of underground construction where factors like water-cement ratio and mix workability are critical. Type A and Type B admixtures are typically water reducers. Type C is a set-retarding admixture which can be advantageous in certain situations but is less commonly subject to restrictions concerning drilled shafts. In contrast, the admixtures classified under Type F, Type G, Type I, and Type II may present challenges in maintaining the necessary balance in a drilled shaft's structural integrity or can lead to adverse reactions with the drilling environment. Thus, using them in this application is not advisable, making the choice of excluding these admixtures not only correct but essential for optimal concrete performance in drilled shafts.