SlumpFlow

SlumpFlow, commonly written as slump flow, is a measure of the flowability of fresh concrete, particularly self-compacting concrete (SCC). It quantifies the spread diameter of concrete after the slump cone is removed and is used to assess workability of the mix.

Method: A standard slump cone is filled with concrete in layers, consolidated, and then lifted vertically. The concrete is allowed to spread freely, and the maximum diameter of the resulting circular mound is recorded as the slump-flow. The procedure follows EFNARC guidelines and related national standards; timing is important.

Applications: Slump-flow is essential in the design and QC of SCC, ensuring the mix can fill formwork and move around reinforcement without external vibration. It indicates potential for good compaction. It does not measure strength directly and cannot ensure absence of segregation or washing out.

Factors affecting results: water content, cementitious materials, aggregate grading and maximum size, admixtures (superplasticizers, viscosity modifiers), temperature, mixing, and elapsed time after mixing. Higher dosage of superplasticizer or finer aggregate tends to increase slump-flow; excessively high flows may increase segregation risk.

Standards and interpretation: Typical SCC slump-flow values lie roughly in the 650–800 mm range, with tighter specification depending on project requirements. Slump-flow is used alongside other tests, such as the V-funnel and L-box, to assess overall workability and passing ability.