Which Aggregate Shape is Best for Your Project?

The shape and texture of the aggregate can have a major impact on the properties of fresh concrete, more so than hardened concrete. Smooth, rounded aggregates are more workable than rough or elongated angular aggregates. Depending on the shape, the aggregate is classified into several categories. The workability of concrete is greatly affected by the shape of the aggregate. In general, aggregates come in a variety of forms, such as angular aggregate, flake aggregate, elongated aggregate, rounded aggregate, sub-rounded aggregate, cubic aggregate, and more.

These aggregates reduce the amount of water needed for a concrete mix, which can also reduce workability but improve its innate strength. The entanglement between the aggregate particles is the best and therefore the bond development is very good. The shape of the aggregates chosen will have a significant effect on the workability of the concrete. However, in Hot Mix Asphalt (HMA), lower interlocking is generally a disadvantage since rounded aggregate will continue to compact, push and groove after construction. At HMA, since aggregates are relied on to provide rigidity and strength when interlocking with each other, angular shaped cubic particles with a rough surface texture are best.

If you need specific advice on the type of aggregates needed for your needs, it's helpful to talk to professionals. This is why rounded aggregate is not suitable for high-strength concrete and for pavements under stress. There are several common tests used to identify and quantify the shape of aggregated particles and the texture of the surface. Lightweight, ultra-light aggregates are more porous than their heavier counterparts, so they can be put to great use in green roof construction, for example. The shape of the aggregated particles and the texture of the surface are important for proper compaction, deformation resistance and workability.

However, the ideal shape for HMA and Portland Cement Concrete (PCC) is different because the aggregates serve different purposes in each material. The entanglement between aggregate particles is better than rounded aggregate but it is not suitable for use in high-strength concrete and stressed pavements. Aggregates form an essential part of many construction projects, from large-scale commercial works to smaller domestic works. Therefore, angular aggregate is very suitable for high-strength concrete and for pavements under stress. However, in PCC where aggregates are used as an inexpensive high-strength material to occupy volume, workability is the main problem with respect to particle shape.

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