How can angular aggregates negatively impact concrete workability?

Angular aggregates can negatively impact concrete workability primarily because their shape and rough texture influence how the particles interact with one another. When aggregates are angular, they create more friction between particles, which can hinder the flow of the concrete mix. This increased friction often necessitates the addition of more water and admixtures to achieve the desired workability for proper placement and finishing.

In contrast, rounded aggregates tend to enable better mobility within the mix, allowing for easier compaction and reduced water requirements. Therefore, when using angular aggregates, the need for additional water and chemical admixtures becomes pronounced to enhance workability, ensuring that the concrete can be effectively mixed, transported, and placed without compromising its structural integrity.

The other options, while they may pertain to concrete properties in other contexts, do not directly affect workability as angularity does. For example, while angular aggregates can influence curing times indirectly by affecting the overall mix characteristics, they do not permanently worsen curing time. Additionally, thermal efficiency and segregation risks are related to other factors in the mix and are not solely attributed to the angularity of aggregates.