Workability of concrete is a physical property of fresh concrete. It refers to the ease with which the mix can be transported, placed and compacted. Workability is influenced by many factors such as water/cement ratio, aggregate size and shape, type of mix design, admixtures, and the method used to prepare the concrete.
In general, higher workability results in a more fluid concrete that can be easily formed into the required shape. This is important when the concrete needs to be pumped or placed using other means such as a roller. A high level of workability also allows the concrete to be placed quickly and without segregation.
The most commonly used measure of workability is the slump test which measures the consistency of a concrete mix. The slump test involves filling a mould in the shape of a frustum of cone with bottom diameter 20 cm, top diameter 10 cm and height 30 cm with concrete which is then tamped down 25 times. The slump of the concrete after this is then measured in mm.
Increasing the water content increases the concrete’s workability by providing more paste that coats the aggregate particles and aids in compaction. However, adding too much water can decrease the strength of the concrete as it inhibits proper hydration and leads to segregation and poor finish.