How does the shape of aggregates affect the workability of concrete?

The shape of aggregates significantly influences the workability of concrete, which is a crucial factor in determining how easily the concrete can be mixed, placed, and finished. Round aggregates tend to improve workability because their smooth surfaces and rounded edges allow them to roll easily over one another, reducing internal friction. This characteristic results in a more fluid mix that is easier to work with.

On the other hand, angular aggregates, which have sharp edges and irregular shapes, create more interlocking and friction between particles. This interlocking can make the mix stiffer and less workable, often requiring additional water or admixtures to enhance workability. Therefore, when using angular aggregates, it is common for concrete mixes to demand more water or higher cement content to achieve the desired consistency and workability.

The other choices do not accurately represent the relationship between aggregate shape and workability. While angular aggregates aren’t universally beneficial for workability, the assertion that shape has no influence on workability or that round aggregates reduce needed cement content also misunderstand the importance of aggregate shape in concrete mixtures. Understanding these nuances allows for better concrete mix designs and construction practices.