Final answer:
True, concrete sold as 3000 psi typically has a higher tested strength in the lab to account for the 'factor of safety', ensuring that it can meet or exceed the specified strength even with on-site variations.
Step-by-step explanation:
The statement that a concrete that is sold as 3000 psi concrete will typically have a lab designed and tested strength much higher is True. Concrete mix designs are often created to exceed the specified strength by a certain margin to account for variability in materials, mixing, handling, and field conditions. This concept is known as the 'factor of safety', which ensures that even with potential variations, the concrete will still meet or exceed the required strength specification. The extra strength also compensates for long-term strength gain, curing conditions, and other factors that may affect concrete after it has been placed.
When 3000 psi concrete is specified, a higher target strength is set during the lab design and testing to ensure this performance level is consistently met in practice. This margin allows for any on-site challenges without compromising the structural integrity of the finished construction.