Why might angular aggregates require additional cement and water?

Angular aggregates typically have sharp edges and a rough surface texture, which creates an increased surface area compared to more rounded aggregates. This characteristic means that they require more water and cement for proper bonding and workability during mixing and placement. The additional cement helps to fill the voids created by the irregular shapes, while the extra water aids in achieving the correct consistency and flow of the concrete. The sharp angles can complicate the mixing process, causing the aggregates to interlock more, which in turn demands a stronger paste to coat and adhere to all surfaces effectively.

In contrast, factors such as density, water retention, or bonding ability may not significantly influence the specific requirements for cement and water when it comes to angular aggregates. Therefore, recognizing the impact of surface texture and geometric shape is critical for understanding the mixing characteristics of different aggregate types.