Which factor most significantly affects the workability of concrete?

The workability of concrete is primarily influenced by the water-cement ratio, which is the correct answer. This ratio refers to the proportion of water to cement in a concrete mix and plays a crucial role in determining the fluidity and ease of placement of the concrete. A higher water-cement ratio typically increases workability, making the mix easier to handle and place, while a lower ratio can strengthen the concrete but may lead to difficulty in mixing and placing it effectively.

The water-cement ratio affects the hydration process of the cement. Adequate water is necessary for the cement to hydrate properly, forming the desired strength and durability of the concrete. If the ratio is too low, the resulting concrete may be too stiff and difficult to work with, leading to problems during mixing and placement. Balancing the water-cement ratio is vital to ensure both workability and the strength of the cured concrete.

While components like the type of aggregate, ambient temperature, and curing duration do influence the overall performance of concrete, none have as significant an impact on workability as the water-cement ratio. For example, certain types of aggregate can affect the concrete's grading and may influence workability, but this is secondary to the influence of the water-cement ratio.