On what basis are mix designs accepted by the department?

The correct answer is based on the idea that mix designs submitted for approval must meet specified requirements outlined in the relevant standards and specifications. These specifications set parameters for the proportions of materials, performance characteristics, and overall quality to ensure that the concrete used in construction will perform as expected under various conditions.

When a mix proposal is aligned with these specification requirements, it demonstrates that it has been carefully formulated to achieve the durability, strength, and workability necessary for the intended application. This compliance ensures that the concrete will meet the structural and safety standards required by the department, thereby supporting the integrity of the construction projects being undertaken.

While factors like yield and cost, federal guidelines, and historical performance are important considerations in the broader context of concrete production and project management, the primary basis for the acceptance of mix designs lies in their ability to meet the specific requirements set forth by the department. This direct alignment with specifications ensures that the materials used will function effectively in the intended environment.