Which factor does NOT play a role in determining concrete strength?

The color of the concrete mix does not influence its strength. Concrete strength is primarily determined by the composition and ratios of its constituents, notably the type of aggregate, the water-to-cement ratio, and the curing conditions.

The type of aggregate used affects the mix's overall performance; different aggregates can impart varying strength characteristics and durability to the concrete. The water-to-cement ratio is a crucial factor since it directly influences the hydration process of cement and the resultant density and strength of the hardened concrete. Proper curing temperature and duration also play a significant role, as adequate curing promotes effective hydration, which is vital for developing concrete strength over time.

While color may affect the aesthetic appearance of the concrete, it does not alter the physical properties that contribute to the strength of the mix. As such, it is the only option that does not pertain to the characteristics that enhance or diminish the strength of the concrete.