Concrete Properties

Concrete Properties

The sub-processes of mixing, transport, moulding and compaction determine the key requirements for the concrete mix and fresh concrete.

Workability is not defined in physical terms and cannot be measured directly. Workability means how easy it is to place, handle, compact and finish the concrete. This notion includes both the rheological properties (i.e. viscosity, yield limit, internal friction) and the behaviour of the concrete mix during mixing, transport, moulding and compaction. Good workability is assumed if the concrete shows good cohesion and no segregation phenomena, and is fully compactable. Workability must be tailored to the specific application and is affected by the amount of cement paste, which acts like a glue and holds or bounds the aggregates together.

As a quantitative measure describing the workability and working time of the concrete, consistency is considered an important characteristic of the concrete mix, to ensure trouble-free transport, spreading and compaction of the mix and to achieve a good surface finish. The main factors that determine the consistency of the concrete mix are its rheological properties and the volume of the cement paste, as well as the type and particle composition of the aggregate. In practice, this adjustment is initially made by defining the water/cement ratio, which expresses the mass radio between the effective water content and the cement content in relation to one cubic meter of compacted fresh concrete.

However, the water/cement ratio alone is not sufficient to determine the consistency and workability of the concrete mix with reasonable certainty, the more paste mixed with the coarse and fine aggregates, the more workable is a mix.

Never try to make a mixture more workable by adding more water because this lowers the strength and durability of concrete.

• water content
• cement content and quality
• well graded aggregates, water demand of the concrete raw materials
• concrete and air temperature